How Food Works

FWHOOOOWRDKS



FWHOOOOWRDKS

Editorial consultant Contributors CONTENTS
Dr. Sarah Brewer Joel Levy, Ginny Smith

Project Art Editors Senior Editor
Duncan Turner Rob Houston
Francis Wong
Editors
Steve Woosnam-Savage Lili Bryant
Wendy Horobin
Designers Janet Mohun
Gregory McCarthy Martyn Page
Francesco Piscitelli
Illustrators
Mark Clifton US Editor
Phil Gamble Margaret Parrish
Mike Garland

Managing Art Editor Jacket Editor
Michael Duffy Claire Gell

Senior Jacket Managing Editor
Designer Angeles Gavira Guerrero

Mark Cavanagh Jackets Design
Development Manager
Producer, Pre-production Sophia MTT
Catherine Williams

Producer Publisher
Anna Vallarino Liz Wheeler

Art Director Publishing Director
Karen Self Jonathan Metcalf

First American Edition, 2017
Published in the United States by DK Publishing
345 Hudson Street, New York, New York 10014

Copyright © 2017 Dorling Kindersley Limited
DK, a Division of Penguin Random House LLC

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copyright owner. Published in Great Britain by Dorling Kindersley Limited.

READER NOTICE
How Food Works provides information on a wide range of food science and nutritional topics and every
effort has been made to ensure that the information is accurate. The book is not a substitute for expert
nutritional advice, however, and you are advised always to consult a professional for specific information on
personal nutritional matters. The authors, contributors, consultants, and publisher do not accept any legal

responsibility for any personal injury or other damage or loss arising from any use or misuse of the
information in this book.

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ISBN: 978-1-4654-6119-3

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Our diet history 8 STORING 46
AND COOKING 48
FOOD 12 50
FUNDAMENTALS 14 How fresh is fresh? 52
16 Preservation 54
Nutrition basics 18 Chilling and freezing 56
Hunger and appetite 20 Fermentation 58
Flavor 22 Raw foods 60
Smell and taste 24 Food processing 62
Digesting nutrients 26 Additives 64
Carbohydrates 28 Cooking
Fiber 30 How food cooks
Protein 32 Safe cooking
Fats 34
Cholesterol 36
Vitamins 38
Minerals 40
Water 42
Convenience foods
Whole foods
Too much or too little?

TYPES OF FOOD

Red meat 68 Phytochemicals 110 DRINKS 152
White meat 70 Leafy vegetables 112 154
Cuts of meat 72 Brassicas 114 Drinking water 156
Processed meats 74 Root vegetables 116 Coffee 158
Meat substitutes 76 The onion family 118 Tea
Fish 78 Vegetable fruits 120 Fruit juice and 160
Shellfish 80 Sweet fruits 122 smoothies 162
Eggs 82 Mushrooms 124 Carbonated drinks 164
Milk and lactose 84 and fungi Energy drinks 166
Yogurt and 86 Nuts and seeds 126 Alcohol 168
live cultures Chilies and 128 Spirits 170
Cheese 88 other hot foods Alcohol and the body 172
Starchy foods 90 Spices 130 Wine
Grains 92 Herbs 132 Beer
Bread 94 Salt 134
Noodles and pasta 96 Fats and oils 136
Gluten 98 Sugar 138
Beans, peas, 100 Sugar highs 140
and pulses and lows
Soy 102 Desserts 142
Potatoes 104 Chocolate 144
Fruit and vegetables 106 Sweets 146
Superfoods 108 Alternative foods 148

DIETS

Balanced diet 176 Detoxing 202 FOOD AND
178 204 ENVIRONMENT
Do we need Popular diets 206
supplements? 180 208 Feeding the world 228
182 Allergies 210 230
Eating patterns 184 212 Intensive or organic? 232
186 Intolerances
Western diets 214 Factory farmed 234
188 Exclusion diets or free-range? 236
Eastern diets 216 238
190 Diet and blood 218 Fair trade 240
Religious and 192 pressure 242
ethical diets 194 220 Food fraud
196 Heart disease 244
Vegetarians 198 and stroke 222 Food waste
and vegans 200 224 246
Diabetes Food miles
Energy budget
Cancer, Genetically
Diet and exercise osteoporosis, modified foods
and anemia
Calorie counting Overfishing and
What to eat during sustainable fishing
Low-carb diets pregnancy
Future foods
High-fiber diet Babies and children

Intermittent fasting Eating disorders

INDEX 248
ACKNOWLEDGMENTS 256

MEAT EATING COOKING

When our ancestors Our ancestors developed
began to eat meat more than cooking before Homo sapiens
2 million years ago, the extra calories evolved 200,000 years ago. Cooking
meat provided, and the reduction in energy made food easier to digest, meaning they
needed for its digestion, may have allowed their could extract more calories from it, and didn’t
brains to become bigger and more energy-hungry, have to spend so much time and energy chewing
as the gut became smaller. However, meat was rare for and processing it. In addition to broadening their diets,
most ancient humans, so they would still have relied cooking may have allowed their jaw muscles and guts to
heavily on plants, including wild grains. become smaller, and their brains to expand further.

800,000 ya 70,000 ya 15,000 ya
Archaeological evidence More widespread evidence
of controlled fire of cooking hearths Invention
of bread
(unleavened)

2 million years ago (mya) 1 mya 500,000 years ago (ya) 50,000 ya 10,000 ya

Our diet history 12,000 ya
Goat domesticated

Diets have changed dramatically during human evolution, often 9,500 ya
causing our bodies to change in response. Dating these changes is Rice cultivated

challenging. Cooking may have originated 300,000 or 1.8 million 9,000 —8,500 ya
years ago, depending on how experts interpret archaeological Sheep domesticated

and genetic evidence. Despite this, scientists are building WHY
a picture of how our dietary history has affected us. ARE MANY

ASIAN PEOPLE

Dietary milestones INTOLERANT TO MILK?

Our anatomy and physiology have evolved as our diet has Intolerance to lactose in milk is

changed over many thousands of years. Some of these pivotal more prevalent in people from
events, such as meat eating or cooking, happened so long ago Asia, because domestic cattle
that our bodies have already evolved accordingly. Whether we were introduced there much
are suited to more recent changes is still to be seen. What has
become clear is that some aspects of the modern diet, with its more recently than in
abundance of energy-dense foods, can be very detrimental to other parts of

our health. Looking back in time may even help us to eat more the world.

healthily today.

GREAT COLUMBIAN EXCHANGE HOW FOOD WORKS 89
Our diet history
When Europeans first
THE SWEET TOOTH

met the native peoples of the For our ancestors, sweet food was a rare delicacy.
Americas in the 15th and 16th Honey and ripe fruits were a great source of
centuries, there began an unprecedented energy, but were scarce or seasonal. Today, we are
exchange of foods that one or the other surrounded by accessible, sweet food all the time,
population had never seen before. Potatoes and and our liking for it has contributed to an epidemic
corn rapidly became staples in the Old World, and of obesity and its related diseases.
sugarcane flourished when taken to the Americas.

8,000 ya EUROPE, ASIA, 1800 bce 997 ce 1911 ce
Cattle domesticated AND AFRICA Chocolate drunk Word “pizza” Home
AMERICAS in Central America first used in Italy
7,000 ya refrigerators
Sugarcane 6,000 ya appeared
cultivated Cheese invented and in the US
alcoholic drinks invented

5,000 ya 1 ce 1000 ce 2000 ce

6,000 ya 4,000 ya 1585 ce
Chicken domesticated Maize cultivated; Chocolate introduced to Europe
leavened bread
8,000 ya invented in Egypt
Potato cultivated

The cultivation of grain allowed Humans have traded food
humans to settle. This made having for thousands of years, but until
more children easier and they quickly fairly recently, only long-life products
out-competed hunter-gatherers in could be transported over extended distances.
most areas. However, their limited diets and The development of refrigeration and freezing,
tightly packed populations meant they had along with faster shipping, have meant that,
poorer health than hunter-gatherers. if you can afford them, foods from all over
the globe can be on your table.

FARMING REFRIGERATED GLOBAL SUPPLY CHAINS



FOOD
FUNDAMENTALS

Nutrition basics

For the body to function normally it requires fuel for energy, building
materials for growth and essential maintenance, plus a small but
vital combination of chemical ingredients to ensure its many
metabolic processes run smoothly. The body can make almost
everything it needs from the nutrients in a balanced diet.

What does the body need? Carbohydrates
Carbohydrates
An adequate combination of essential are the body’s
nutrients in our diet—water, carbohydrates, primary source of
proteins, fats, vitamins, and minerals—should energy. The body converts simple
enable our bodies to work efficiently and keep sugars and more complex starches
us in good health. Beyond basic nutrition, into glucose, which fuels our body
there are other nutrients that, although our cells. Whole grains and fruits and
body doesn’t necessarily need them, are vegetables that are high in fiber
certainly beneficial, such as phytochemicals are the most healthy sources
in fruit and vegetables and fatty acids in some of carbohydrates.
fish. Nutraceuticals, or “functional foods,”
including those containing probiotics SUGAR
(see p.87), are believed to have health
benefits beyond their nutritional value, Water LARGE INTESTINE
including disease prevention. Around 65 percent
of the body is made
MALNUTRITION up of water. This is
constantly being lost
Malnutrition results from a diet through digestion,
that does not contain the right breathing, sweating,
amounts of nutrients. While lack of and urine, and it is
carbohydrates and protein can lead critical that water
to major development and growth is replenished at
problems, deficiency in certain regular intervals.
vitamins and minerals can cause
specific illnesses. For example, a
lack of iron may lead to anemia.
Overnutrition occurs when an
oversupply of nutrients causes
health problems, such as obesity
caused by a high-calorie diet.

Minerals
Present in a wide variety of foods,
minerals are vital for building bones, hair,
skin, and blood cells. They also enhance

nerve function and help to turn food
into energy. Deficiencies can cause
chronic health problems.

FOOD FUNDAMENTALS 12 13
Nutrition basics

Getting what we need Building and maintaining cells
When we eat food, it passes into our
digestive system to be broken down and Cells are the basic functional units of the human
absorbed (see pp.20—21). Most nutrients body that make up its diverse tissues and organs.
are absorbed in the small intestine. Every one of our trillions of cells is built and
maintained by the nutrients we get through our
diet. If, through poor nutrition, our cells are unable
to function properly, our tissues and organs can
become compromised, leading to the onset of a
host of health conditions and diseases.

Proteins CELL MEMBRANE Cell support
Proteins are broken down into amino CYTOPLASM A broad range of nutrients
acids. Although they may be used by support cell formation and
the body for energy, their main role NUCLEUS growth. A cell’s main
is as building blocks of tissue growth structures are built from
and repair. Healthy protein sources CELL STRUCTURE amino acids and some
fatty acids, and every cell
include beans, lean meat, is fueled by carbohydrates
and other fatty acids.
STO dairy, and eggs.
MACH

AMINO 1 in 3
ACIDS
THE PROPORTION OF
SMALL INTESTINE FATTY Fats PEOPLE WORLDWIDE
ACIDS Fats are a rich source of energy and help THAT SUFFER FROM
in the absorption of fat-soluble vitamins. MALNUTRITION
Essential fatty acids cannot be made by
the body and must be obtained from
food. The healthiest fat sources

include dairy, nuts, fish, and
vegetable-based oils.

Vitamins WHAT IS A
Vitamins are vital “HEALTHY DIET”?
to the body’s
metabolic processes, A healthy diet is one that
especially those linked to tissue growth provides the body with the right
and maintenance. Most vitamins can’t
be stored in the body, so regular amounts of all the essential
intake through a balanced diet is nutrients it needs from a variety
essential. As with minerals, a lack
of certain vitamins can lead of different food sources. This
to deficiency diseases. should help you achieve and

maintain a healthy
body weight.

Hunger BRAIN
and appetite

Hunger is vital to our survival, and it ensures 1 Hunger triggers
we eat enough for our bodies to function. But a Seeing food can trigger
lot of the time we eat not because we are a desire to eat whether or not
hungry but because we enjoy food—this is we are hungry. (The same
down to our appetite. response is triggered by
anticipation of a mealtime).
Hunger and satiety The food passes to the stomach
via the esophagus.
Hunger is controlled by a complex interconnected system
including our brain, digestive system, and fat stores. The desire HUNGER GHRELIN
to eat can be triggered by internal factors, such as low blood
sugar or an empty stomach, or external triggers, such as the KEY Vagus nerve
sight and smell of food. After we have eaten, satiety, or “fullness” Ghrelin
signals are produced, which tell us we have had enough. Insulin Movement
Leptin of food
Hunger vs. appetite
2 Empty stomach
Appetite is different from hunger, but the two are linked. Hunger When the stomach has been
is the physiological need for food, driven by internal cues such empty for around 2 hours, the gut
as low blood sugar or an empty stomach. Appetite is the desire muscles contract, clearing out any
to eat, driven by seeing or smelling food or something we link last debris. Low blood sugar levels
with it. Memory for how much we have eaten is also important exacerbate the feelings of hunger.
in appetite, and people with short-term memory loss may eat Levels of a hunger hormone called
again soon after eating. Stress can also increase the desire to ghrelin also rise.
eat. Some substances can help control appetite by specific
actions on the body.

Water Grapefruit SMALL INTESTINE PANCREAS
Water stretches the stomach, The scent of grapefruit
triggering satiety. Satiety is seems to reduce activation
short-lived, since water is of the vagus nerve,
quickly absorbed and the body reducing appetite.
responds to the lack of nutrients. Nicotine
Fiber Nicotine activates
Foods high in fiber slow the receptors in the
emptying of the stomach and hypothalamus, reducing
delay the absorption of nutrients, hunger signals.
keeping you fuller for longer.

Protein Exercise
Protein affects the release of High-intensity aerobic
various appetite-regulating exercise affects the
hormones such as leptin, release of hunger
increasing feelings hormones, temporarily
of fullness. suppressing hunger.

FOOD FUNDAMENTALS 14 15
Hunger and appetite

Hypothalamus receives “full” APPETITE AND OBESITY
signal from vagus nerve

Brain receives People with a tendency to Hunger
“full” signals
6 obesity may respond differently stimulated by
external cue
to external hunger cues. They
The vagus nerve sends signals
straight to the hypothalamus, may also be less sensitive to

telling the brain that food has the fullness hormone, leptin.

been consumed and reducing Unfortunately, taking leptin as

the hunger drive. a drug doesn’t help obesity. The

body quickly adapts to be even

more insensitive to leptin,

even at high doses.

Leptin released

to no response ADIPOSE TISSUE

LEPTIN SATIETY

5 Leptin travels Cravings
to brain
Fat cells release a hunger-inhibiting Cravings are a dramatic and specific
hormone called leptin. After eating, desire for a certain type of food, and
more leptin is secreted and we feel most of us have experienced them.
INSULIN full. (Conversely, leptin levels Occasionally, they are caused by specific
VAGUS NERVE decrease with fasting, making us nutrient deficiencies, and may be the
feel hungry.) body’s way of telling you about the
problem. But mostly they are purely IRON
STOMAC 4 Pancreas psychological, driven by stress or CHALK
releases insulin boredom. Normally, craved foods are
The stretching stomach high in fat or sugar (or high in both),
H STRETCH RECEPTORS and the rise in glucose which trigger a rush of pleasurable
in the bloodstream, chemicals in the brain when eaten.
triggers the release of It may be this feeling that we crave
insulin. This allows the rather than the actual food.
conversion of glucose to
glycogen (in the liver) and
then to fat. Insulin may
also make the brain more
sensitive to satiety signals.

ADIPOSE WHY DOES MY
(FAT) TISSUE STOMACH RUMBLE
WHEN I’M HUNGRY?
3 Stomach stretches SOAP
As the stomach fills, After eating, your stomach Strange tastes
stretch receptors detect muscles contract to push food Some people, especially
expansion, causing hunger- through to the intestines. With pregnant women or very
reducing chemicals to be young children, experience
released. (Liquids, including an empty stomach, this still cravings for nonfood
water, stretch the stomach happens, but with nothing to substances, including soil,
temporarily, but are quickly chalk, iron, and soap.
absorbed, so hunger returns.) dampen the sound, you Psychiatrists call this “pica.”
Glucose released hear the growls!
into bloodstream
from digested food

Flavor Sour
Vietnamese dipping sauce
We eat food not only because we need to, but also uses a mixture of sour lime juice,
because we enjoy it, and this is at least in part down salty fish sauce, and sweet palm
to its flavor. Flavor is a combination of the taste and sugar, along with garlic and chili, to
smell of food, which combine with input from our activate almost all the receptors on
other senses to produce a pleasurable experience. your tongue at once. Sour tastes are
produced when taste buds detect
What gives food flavor? hydrogen ions. These come fromDIPPIN
acidic foods such as fruits
You detect smell when volatile chemicals travel into your nose—
either before you eat the food or when it is in your mouth. At the and vinegar.
same time, the tongue and mouth detect five basic tastes, which G SAUCE
combine with the smell to produce flavor. Other senses contribute
too—touch and hearing tell you about the food’s texture. Even the MANGO
color of a food can impact how we perceive flavor— STRIPS
a study showed that changing the color of
orange squash affected people’s ability
to identify its flavor correctly.

COULD THERE BE Sweet VIETNAMESE MANGO SALAD
UNDISCOVERED TASTES? Another of the basic tastes is
sweetness. Your sweet receptors
It is quite likely; some argue respond to sugars such as fructose
that metallic tastes are a (in fruit) and sucrose (table sugar).
separate category, while Some artificial sweeteners, such
calcium’s chalky taste can as aspartame, taste much sweeter
be detected by mice and than sugar, meaning you can
possibly humans, too.
use less in foods.

DRIED
SHRIMP

“NEW” TASTES

Recently, receptors have been found on our tongues Umami
Umami is the most recently
that bind to fatty acids, producing a taste of “fattiness.” discovered of the basic tastes—
the name is Japanese, and it roughly
Whether this is a true sixth taste is still under debate. translates as “savory.” Glutamic acid
in foods is detected as umami and it is
Another recent study suggested found in high quantities in fermented
and aged foods such as dried
humans can also taste starch, FRIES
but a receptor has not yet been shrimp, soy sauce, and
Parmesan cheese.
found. Oil-fried chunky fries

may trigger both of these

proposed new classes of taste.

FOOD FUNDAMENTALS 16 17
Flavor

TOMATOES RELEASE 222 Non-taste sensations
VOLATILE CHEMICALS
THAT GIVE THEM In addition to the five basic tastes, our tongues
THEIR FLAVOR and mouths can detect some other sensations
that are not classified as tastes. Nerves on the

tongue detect temperature, touch, and pain,

Bitter and foods that activate these nerves
Children often find bitter produce specific sensations. For example,
foods unpleasant, but many the carbon dioxide in carbonated drinks

adults enjoy bitter tastes such as tea doesn’t only activate our sour taste
(including green tea), coffee, and dark receptors. Its bubbles also cause touch
chocolate. It is the most sensitive taste, receptors to fire. The two combine to

probably because it evolved to
prevent us from eating bitter-
tasting poisonous plants. produce the fizzy sensation.

SPRING ROLLS SENSATION EXPLANATION
ETNAMESE TEA Astringent
Chemicals in tea and unripe fruit cause a
puckering sensation of the mucous membrane
and disrupt the saliva film, making the mouth
feel dry and rough.

VI

VIETNAMESE Cooling Menthol in mint sensitizes the cold receptors on
TEA Spiciness your tongue, giving a cool, refreshing sensation.

Capsaicin chemicals in chili stimulate pain
and heat receptors on the tongue, causing
a burning feeling.

SALTED PE Numbness There is a disagreement as to the cause, but
Sichuan pepper produces numbness or a tingling
ANUTS sensation, possibly by stimulating light touch
receptors.

Salty Smell and flavor COFFEE
Table salt is sodium chloride, CHOCOLATE
and we have sensors in our The smell of food can be different
mouths that detect sodium ions. from its taste, despite most of a
They are also triggered (though food’s flavor coming from its smell.
less strongly) by closely related This is because when food is in
atoms, including potassium. our mouth, scent molecules travel
up the back of the throat rather
than through the nose (see p.19).
This changes which molecules we
detect, and in what order, creating
a difference in the scent perceived.
This is particularly noticeable in
coffee and chocolate.

Smell and taste

Molecules in food dissolve in saliva and register as tastes when
they come into contact with your tongue. Airborne volatile
molecules released by food are detected by your nose as smells.

Perceiving our meals Mucus- Supporting
secreting gland cell
Molecules released by food in the air or by
chewing dissolve when they meet moisture, MUCUS ROELCFEAPCTTOORRSY
such as mucus in the nose and saliva in
the mouth. They can then be detected Scent molecule Scent molecule OLOFRATCHTIOONNASAL Scent molecule
by specialized nerve cells. These cells dissolving in binding to CHEWED
transmit electrical signals to the brain, mucus receptor FOOD
which identifies and categorizes each smell
and taste. Our noses can pick up hundreds Food particle Supporting cell TONGUE
of different kinds of smells, but our tongues
primarily detect five tastes—possibly more SALIVA
(see pp.16–17).

Olfactory receptor cell

How smell works
Your nasal cavity has a thin layer of mucus.
When scent molecules dissolve into it, they
bind to the ends of olfactory receptor cells.

WHY DOES THE
SMELL OF COOKING
MAKE YOU SALIVATE?

When you smell food, sensory
information is passed to the

brain, which sends nerve signals
to the salivary glands. Saliva is

produced to prepare
for the first stages
of digestion.

T

ASTE BUD

How taste works
The tongue’s surface is full of taste
receptor cells. Chemicals from food
and drink dissolved in saliva come
into contact with these cells.

Taste receptor cell Sensory nerve

FOOD FUNDAMENTALS 18 19
Smell and taste

ONE PAPILLA Why do foods have FRESH ROTTEN
ON THE TONGUE CAN tastes and smells?
CONTAIN HUNDREDS Fresh or rotten?
OF TASTE BUDS As the first humans evolved, they made Distinguishing between fresh
a wide range of food choices every day. (nutritious) or rotten (potentially
To the brain This means we have evolved more taste dangerous) fruit would have
Olfactory receptor cells in the receptors than animals who stick to one been helpful for our ancestors.
nose and taste receptor cells on the type of food. As infants, we like sweet
tongue send nerve signals to the tastes and reject bitter ones—this is
brain to register smells and tastes. thought to stem back to our evolutionary
past where sweet tastes signaled high-
TO BRAIN energy foods and bitterness could be a
NERVE SIGNA warning for poison. Our desire for salty
and umami (savory) tastes are thought
to be driven by our need for salt and
other minerals, and for protein.
LS
SWEET SALTY BITTE R

MUCUS E SIGNALS TO BRAIN
ORLEFTARCOTNIOANSAL

NERV High calorie Vital minerals Sign of poison
Sweet foods such as A taste for salt exists Typically, bitter tastes signal
honey provide high because sodium is one of poisonous foods, but with
amounts of calories. the macrominerals we experience we can learn to
need to survive. like some bitter tastes.
SALIVA

Smelling in reverse WHY DO MEALS ON PLANES TASTE BLAND?
Food in the mouth releases scent
molecules that waft up the back The dry air on a plane makes our
of the throat (retronasal olfaction) mouths dry and our noses stuffy,
rather than through the nose interferring with the moist media in
(orthonasal olfaction). Most of which molecules from food and drink
what you taste is actually made dissolve. This means taste and smell
up of smells detected via receptors don’t detect molecules
retronasal olfaction. properly. Our sensitivity to sweet and
salty foods drops by 30 percent on
planes, so in-flight meals are often
salted to give them an extra kick. Oddly,
umami tastes seem to be unaffected.

Digesting nutrients 1 Into the mouth
Chewing breaks food down
For your body to absorb nutrients, food must first be broken down— into smaller particles. This creates a
this is the process of digestion. Most of the food you eat will reach larger surface area for our digestive
your bowel within a few hours, but how long it stays there varies enzymes to work on. Enzymes in the
from person to person. Carbohydrates, proteins, and fats all break saliva begin breaking down starches
down at different stages of the process—fiber stays relatively intact. (types of carbohydrate) and fats.

Teeth chew food SAGLILVAANRDY

Enzyme
digests
starch

What happens when we eat? KEY Saliva Enzyme
Fat produced digests fat
A combination of chewing, crushing, churning, and Carbohydrate by salivary
the action of digestive enzymes breaks down large food Enzyme
molecules into smaller ones that can be absorbed into Protein gland
the bloodstream. Each enzyme has a specific shape, which Fiber
means it can only break down certain molecules, so we Muscles in throat push
have a number of different types working in our bodies— chewed food down into
all the way from our mouth to our intestines.
the stomach

LIVER ALLBLADD Churning OMACH ESOPHAGUS
The stomach moves,
G 2 Enzyme digests
ST proteins
ER
BILE DUCT churning the food and breaking
it down further. Acid in the
gastric juices and enzymes
released by glands in the
stomach work on proteins and
fats, helping turn them into
amino acids and fatty acids.

3 Releasing juices FATTY GASTRIC AMINO
The liver produces bile, and the ACIDS JUICES ACIDS

gallbladder stores and concentrates it. UNDIGESTED Enzyme
Acidic liquid from the stomach is neutralized FIBER digests fats
by bile, which is alkaline, before it passes
through the intestines. Bile also plays an Gastric juices contain
important role in digesting fats. enzymes that digest
protein and fat

PANCREAS 4 Enzymes in action
Bile breaks up fat droplets to
help the enzymes process them. In
the duodenum (the first part of the
small intestine), enzymes from the
pancreas digest carbohydrates,
DUODENUM proteins, and fats.

KEY 5 Absorption Fat globules
Simple sugars Next, the mostly digested liquid full of simple emulsified
Amino acids sugars, amino acids, fatty acids, and undigested fiber by bile
Fatty acids passes along the small intestine, where the majority
Enzyme of the nutrients and water are absorbed into the Enzyme
Water bloodstream. Fingerlike protrusions called breaks
Vitamins VILLI villi increase the surface area of the walls, down fats
SMALL INTESTINE helping with absorption.
Enzyme
Nutrients FATTY breaks down
absorbed by villi ACIDS proteins

Nutrients absorbed in UNDIGESTED Enzyme breaks AMINO FOOD FUNDAMENTALS
blood travel to parts of the FIBER down sugars ACIDS Digesting nutrients

body that need them SIMPLE
SUGARS
Water BLOOD VESSEL
absorbed Vitamins
HOW MUCH absorbed 6 Fermentation
FOOD CAN THE Feces pass slowly through the
STOMACH HOLD? large intestine, allowing bacteria to
ferment indigestible fiber. Any final
water and vitamins (including those
Most stomachs can produced by the bacteria) are 20 21
absorbed, and the remains are
comfortably fit around 2 pints compacted as waste.

(1 liter) of food, but some UNDIGESTED
FIBER
stomachs can stretch to
BACTERIA
accommodate much
RECTUM
larger meals. LARGE

INTESTINE

Carbohydrates DO CARBS

MAKE YOU FAT?

Most of the food we eat contains carbohydrates. Carbohydrates can cause you
They include sugar and starches, which provide to gain weight if you eat too
our body with energy, and fiber, which is vital many of them, but complex,
for a healthy digestive system.
high-fiber carbohydrates

are a key part of a

What are carbohydrates? healthy diet.

Carbohydrate molecules are made STARCHES

up of carbon, hydrogen, and oxygen

atoms, often in the form of

hexagonal or pentagonal rings. Unrefined starches Refined starches
If the rings are in ones or twos, These are found in foods Only the simpler, more easily
they are sugars, but if the rings including whole-grain breads, digested starches are found in
combine into unbranched or cereals, and beans. They are broken refined carbohydrates such as
branched chains, they become down slowly, releasing energy over a white flour and white rice. They break
starches and other complex long period of time. They are also a good down easily in the body, giving a quick
source of fiber, vitamins, and minerals. energy rush, but don’t keep you full for long.

carbohydrates. Very long,

indigestible chains make up

dietary fiber (see pp.24–25). In the WHOLE GRAINS BEANS AND WHITE CAKE WHITE
body, sugars and starches are RICE BREAD
converted into the sugar glucose— LEGUMES SUGARS

our body’s primary source of energy.

NOT ENOUGH CARBS? Milk and natural sugars Free sugars
Natural sugars are found in milk These can be added to food as refined
If you don’t eat enough carbs, your products, fruit, and some vegetables. table sugar, but are naturally present in
liver converts fats into ketones and The fiber in some of these foods honey, syrups, and fruit juices. These
protein into glucose, which are ensures that the sugar is absorbed provide lots of “empty calories” and it is
used to generate energy. Ketogenic at a gradual rate. easy to eat too much of them.
diets can help weight loss, but not
much is known about their long- APPLE BROCCOLI MILK HONEY FRUIT SYRUP
term health effects. They can also JUICE
give you smelly breath!
FIBER
Ketone
released A LOW-CARB DIET MAY LEAD TO
in breath MOOD SWINGS AS CARBS HELP
THE BRAIN MAKE A CHEMICAL
Smelly breath THAT STABILIZES MOODS
caused by ketones

FOOD FUNDAMENTALS 22 23
Carbohydrates

How the body uses carbohydrates BRAIN The brain is the
body’s most energy-
When we eat carbohydrates, our digestive tract breaks them down demanding organ
into sugars, which are absorbed into the blood. Glucose is used
directly by our various organs and muscles as a source of energy. 3 Using energy
Fructose—a simple fruit sugar that bonds with glucose to make Glucose is the
table sugar—can only be processed by the liver. People with easiest and most
high fructose diets are at higher risk of type 2 diabetes, possibly efficient fuel for the
because fructose is more likely to be converted into fat. body. Chemical

reactions in our cells
convert glucose (or
SMALL INTESTINE other molecules if
glucose isn’t available)
1 Absorption and into molecules that
distribution release energy.
Long-chain, starchy
carbohydrates need to be
broken down into sugars
to be absorbed. Digestion
begins in the mouth and
continues into the small
intestine, where the sugars
pass into the bloodstream. MUSCLE

Glucose BLOOD VESSEL Fructose Muscle cells
molecules molecules convert glucose
travel in the travel in the
blood into energy
blood
Glucose is used or HEART
VER stored by the liver
The heart uses
LI energy to pump
nutrients around
the body

Glucose travels
around the body

Some glucose is stored
as glycogen, a complex
carbohydrate like starch

FAT

Fructose is either 4 Fat stores
converted to glucose Once the liver’s
or stored as fat glycogen stores are full, excess

2 The liver’s role glucose is converted into fat
If we eat more carbohydrates than we and stored around the body,
need to use immediately, the liver stores the
excess as glycogen. When blood sugar levels to be used as fuel later if food
becomes scarce.
drop, the stored glycogen is converted back
into glucose to be used by the body.

Fiber Skin of your greens
In many plants, the most fiber-rich part
Fiber is the part of food that is not broken is the skin. Apple skins, for example, are
down by the body, and helps keep your a great source of the insoluble fiber
digestive system functioning properly. It cellulose. This type of fiber provides
is found in varying amounts in plant foods. structure to the apple's cell walls.

APPLE

APPLE CELLS

Types of fiber

Fiber is traditionally characterized into two types. Soluble fiber dissolves in

water, making a thick gel. It is found in foods such as fruit, root vegetables,

and lentils, and prevents constipation by softening stools. Insoluble fiber is

found in foods like cereals, nuts, and seeds. It keeps bowels healthy by Cellulose Plant cell
increasing the weight of stools. However, studies have shown that there strands provide
is crossover between the two categories and that solubility doesn't always
predict how a type of fiber will behave in the body. structure to
cell walls

Chain

FIBER STRANDS CELLULOSE STRANDS

CELLULOSE STRAND

Sugar molecule

Fiber strands Holding it together
Fiber is a carbohydrate comprised of The long strands of cellulose in
long chains of sugar molecules. However, apples bond together to form a
unlike other carbohydrates, they resist rigid framework, which provides
digestion in the stomach. This means they support for the cells.
reach the large intestine intact.

GETTING ENOUGH FIBER

Many of us don’t get enough fiber in our diets.
Whole grains are the most common source, but
refined grains have the fiber-rich outer layer removed,
so don’t provide much. The UK recommends 5⁄8oz
(18g) a day—although recommendations vary.

KEY 5⁄8oz (18g) Amount required to WHEAT CEREAL DRIED FIGS CHICKPEAS BROWN BREAD
of fiber reach 5⁄8oz (18g) of fiber 63⁄4oz (186g) 91⁄2oz (260g) 15oz (15oz) 181⁄2oz (514g)

FOOD FUNDAMENTALS 24 25
Fibre

COMPLEX FIBER FERMENTING IN COLON

VITAMIN K

Vitamin production Feeding your intestines bacteria Protection
Certain strains of bacteria produce Weak acids produced by
vitamins, some of which we can Fiber is an important source of food for your gut fermentation make the colon
absorb and use. We get some flora (microbes including bacteria and fungi that less hospitable to bad bacteria,
of our Vitamin K this way. live in your intestines) which ferment it into lowering the risk of stomach bugs.

FATTY fatty acids they can feed on. Keeping these FATTY
ACIDS bacteria healthy is vital—they produce ACIDS
enzymes to help digest other foods and
influence your health in ways that
we are only just beginning
to understand.

Healthy colon Improving immunity
More beneficial bacteria in the Some types of bacteria in your
colon increases the mass of gut improve your immune system
stools, diluting toxins and by producing inflammation-
keeping the bowel healthy. reducing compounds.

Fiber and health Cholesterol BLOOD VESSEL

Eating plenty of fiber (see pp.198–99) IVER Fiber
reduces the risk of heart disease,
certain cancers, obesity, and type 2 L
diabetes. A high-fiber diet counters
the increased risk of colon cancer
caused by eating processed meat
(see p.219).

Unexpected benefit BILE DUCT SMALL
Fiber, particularly the soluble kind, binds to INTESTINE
bile (a bitter liquid that breaks fats down Cholesterol pulled
to tiny droplets), causing it to be excreted. To into the liver in order Fiber and bile
replace the bile, the liver must pull cholesterol to produce bile excreted
out of the bloodstream, which may explain
how fiber lowers the risk of heart disease.

Protein HOW MUCH

Protein is a vital nutrient. The proteins we eat PROTEIN DO WE
are broken down into their building blocks and NEED EACH DAY?
used to make new proteins and other complex
molecules needed by the body. While protein can People need around 1g (1⁄32oz)
serve as an energy source, its main function is in of protein for each 1kg (21⁄4lb)
the creation, growth, and repair of human tissues. of body weight. This would
be 55g (2oz) for the average

man and 45g (11⁄2oz) for

LE the average woman.

What is protein? PROTEIN MOLECU
A
Proteins are chains of small S H O R T PEPTIDE CHAIN

molecules called amino acids.

While only 21 standard types

of amino acid occur naturally in MINO ACIDS
humans, they can join together
in any combination, meaning that

there are millions of different

types of protein available.

When you eat foods containing

protein, your body breaks them

down into amino acids, then Bond between Free amino acids,
reassembles them into different two amino with all peptide
sequences, producing whatever acids
types of protein it needs. bonds digested away

An important property of proteins

is their ability to fold and twist in Protein Protein fragment Protein components
on themselves, which gives each Proteins are giant, complex Shorter chains of amino acids Amino acids are small
protein its distinctive shape. This molecules made of many are called peptides. They form molecules made mainly of
is what allows proteins to have so amino acids connected in when protein is digested, but carbon, oxygen, hydrogen,
many different uses in the body. a chain, which often folds the body also makes them for and nitrogen. There are
into a compact shape. many purposes. 21 types in the human body.

Why are certain amino ll essential amino acid Eight amino acids Eight amino acids
acids “essential”?
A s
At some point in our evolutionary
history, we lost the ability to BEEF WHEAT LEGUMES
make nine of the amino acids
our body needs. This means we Complementary protein sources
must consume these “essential” Some foods such as beef have all the essential amino acids you need, but others do
amino acids in our food. Proteins not. Wheat is low in the amino acid lysine but high in methionine, whereas legumes
containing an abundance of all tend to have enough lysine but have lower levels of methionine. Combining these
nine of them are called “complete.” two sources of protein can provide all the essential amino acids you need.
Most animal products are complete
proteins, but so are quinoa, tofu,
and some nuts and seeds.

FOOD FUNDAMENTALS 26 27
Protein

How we use protein DNA PROTEIN IS
The body converts some PRESENT IN
Dietary protein, once digested amino acids into chemical “bases,” EVERY ONE
into amino acids, is involved in which, once assembled in order, OF OUR BODY’S
making a huge number of vital are the components of DNA that TRILLIONS
molecules, from DNA to hormones spell out its genetic code. OF CELLS
and neurotransmitters. Most
amino acids, however, are Base within
assembled into new proteins. DNA
Some of these form the structures
of our body, such as muscles. DNA STRAND
Many others act as enzymes—
molecular catalysts that trigger
and control the body’s vital
chemical processes.

Cell membrane proteins Hormones
A cell’s membrane is its outside Our body uses hormones to send
layer. Proteins embedded in it messages between different areas.
allow communication with the Many hormones, including adrenaline,
cell’s surroundings—for example, are proteins or peptides. They are
by allowing molecules to pass across. made by glands and organs.

CELL PROTEIN MEMBRANE Adrenaline

ADRENAL
GLANDS
KIDNEY

AMINO ACIDS

Muscle proteins NERVE
Muscles are made mainly of straight, CELL
long-chain proteins, which form muscle
fibers. We need to eat proteins to build our Neurotransmitter
muscles, and also to repair damage that Neurotransmitters
our muscles suffer when we use them. Some amino acids are used to
make neurotransmitters, which
MUSCLE are molecules that carry messages
between nerve cells throughout
our brain and nervous system.

Fats

Fats are essential for our body’s health. They provide

energy, store excess calories for later use, and have

a variety of other roles in the body, from forming cell

membranes to making hormones. Carbon

atom Glycerol holds the three fatty
acids together until they are
What are fats? broken down in the body

Along with carbohydrates and proteins, GLYCEROL Hydrogen
fats make up one of the three main classes of atom
macronutrients. Fats in food come as triglyceride
molecules. These are made of carbon, hydrogen, SATURATED FATTY ACID Oxygen
and oxygen atoms arranged so the carbons MONOUNSATURATED FATTY ACID atom
form three long chains called fatty acids, POLYUNSATURATED FATTY ACID
joined by a short chain called glycerol. Each Omega end—
carbon can bond to other carbons with a the carbons
single or a double bond; the number and
position of these double bonds changes in the chain are
the type of fatty acid and its effect counted from here
in the body. The fatty acids making
up a fat molecule can be the same or
different, giving a huge number
of possible types of fat.

Fat molecule
This triglyceride, or fat molecule, has one
of each type of fatty acid. The straight
one is a saturated fatty acid, made only
of single bonds. If a chain has one
double bond, its shape is bent and it
becomes a monounsaturated fatty
acid. More double bonds make
polyunsaturated chains with
complex shapes.

WILL FAT Bent fatty acids, such The third carbon
MAKE ME FAT? as oleic acid, found in from the omega

Fat is highly calorific, so olive oil, have one end is the first
can contribute to weight gain, double bond with a double
but compared to sweet foods, bond, making this
Stearic acid, found in meat, is polyunsaturated
it makes you feel full for chain an omega-3
longer after eating, so a little fully saturated with hydrogen—
fat may help stop you from fatty acid
there is no room for any more
snacking later! hydrogen atoms Each carbon-carbon double
bond excludes two hydrogens,

which would otherwise bond with

the carbons; since it is short of two

hydrogens, it is not saturated with

hydrogen—it is “unsaturated”

FOOD FUNDAMENTALS 28 29
Fats

Fats in the body Brain and nervous tissue ESSENTIAL FATTY ACIDS
are rich in fat—the brain
In addition to their use as energy is 60 percent fat and The human body can make most of
stores, fats play many other crucial needs a steady supply the fats it needs from other fats or
roles. Fats help us absorb and use raw materials. Only two fatty acids
some vitamins (see pp.32–33) and are BRAIN are truly essential, because we can’t
involved in constructing and repairing make them—the omega-3 fatty acid,
nervous tissue. They maintain healthy Steroid hormones, alpha-linolenic acid and the omega-6
skin and nails and are used to make such as testosterone fatty acid, linoleic acid. Both
hormones that control blood and estrogen, are are found in nuts and
pressure, the immune system, made from fats seeds, especially linseed.
growth, and blood clotting. Some other omega-3
Fats also form the basis of all oils are almost
the membranes in the body, essential because the
surrounding each cell and the body isn’t very good
structures within it (see p.30). at making them (see
fish, pp.78–79).
Fat is stored in subcutaneous FAT STORE
(under-skin) deposits and also in FLAX PLANT,
deeper deposits around organs SOURCE OF LINSEED

Fat or oil? MORE THAN
20 TYPES OF
The word fat is often used to describe items that are solid at room FATTY ACIDS
temperature, such as butter and lard, while oils are liquid. As a rough ARE FOUND
rule, oils contain more unsaturated fatty acids. For many years, it was IN FOODS
common to solidify vegetable oil by hydrogenating those fatty acids
to make margarine—a supposedly healthy alternative to butter. The A trans fatty acid is often
fats produced have since been found to be so unhealthy that straightened, but with a kink
margarine is now solidified by adding naturally solid palm oil instead.

Oleic acid is bent Stearic acid is straight

Oils Fats Hydrogenated fats
Unsaturated fats have at least Saturated fats contain no double Trans fats are made by
some fatty acids with at least one bonds, and their chains are straight. hydrogenating vegetable oils—
double bond. They are found in Their molecules pack tightly, so they a process that adds hydrogen to
vegetable oils, nuts, and seeds. The solidify easily, forming solids at room unsaturated double bonds, saturating
bends introduced by their double temperature. They are found in animal them and straightening their chains.
bonds give their molecules awkward products, such as butter and meat, This forms solid fat, such as that in
shapes that do not pack together, and also in palm and coconut oils. margarine. Trans fats have been
linked to a range of health issues
so they stay liquid at room BUTTER and are being phased out of
temperature.
many products.
OLIVE OIL
MARGARINE

Cholesterol

A waxy, fatlike substance found in CHOLESTEROL IN THE DIET
every cell of our bodies, cholesterol
is made by the liver, and it is vital for Humans can make all the LIVER DIET
normal body function. If too much cholesterol they need mainly 67–75% 25–33%
builds up in the blood, however, in the liver, but they gain extra
problems such as heart disease can in the diet—either directly
result. But the link between diet, from foods such as eggs
cholesterol, and cardiovascular health and meat, or, in some
is more complex than we thought. people, because saturated
fats, trans fats, and some
carbohydrates boost their
liver’s cholesterol production.

Crucial chemical Fluid inside cell Cell membrane
is water-based is a thin, flexible
Cholesterol is needed to manufacture some hormones, outer envelope
vitamin D, and bile acids, which form an ingredient of Small structures
digestive juices (see pp.20–21). It also keeps our cell within cell are
membranes—the thin layer surrounding every cell—
flexible but firm. The liver regulates our cholesterol each enclosed by
level, regardless of cholesterol in the diet, but a diet too a membrane
rich in certain foods can make some people produce
too much (see p.214).

CELL MEMBRANE Membrane made mainly CELL Internal membranes are
of oily chemicals called made the same way as
phospholipids the cell membrane

MEMPRBORTAENINE Cholesterol stiffens Cell membrane
the central part Each of our cells has a membrane
formed of two layers of molecules.
Cholesterol embedded within these
layers prevents the membrane from
becoming too fluid or too stiff, and gives
it just the right permeability to allow the
correct types and numbers of minerals
and other substances to pass through. It
also helps certain proteins attach to the
cell—these are vital for communicating
with the rest of the body.

THE HUMAN BODY
CONTAINS AROUND
40Z (100G) OF
CHOLESTEROL

FOOD FUNDAMENTALS 30 31
Cholesterol

Cholesterol Protein

Transporting fat Cholesterol

Fatty substances, including cholesterol, Protein
cannot mix with our water-based body fluids,
so they need to be bundled into a water- Phospholipid Phospholipid
friendly capsule to be transported around the Low-density lipoprotein (LDL)
body. Cholesterol is packaged into tiny High-density lipoprotein (HDL) These larger particles contain more
capsules called lipoproteins, which come in HDL particles are dense, because cholesterol, and a smaller proportion
two major types. The larger type, LDL, is they contain more protein and less of their weight is protein.
referred to as “bad cholesterol,” because its cholesterol and other fatty parts.
function is to deliver cholesterol to the blood,
where excess can build up. HDL, or “good
cholesterol,” takes cholesterol out of the blood.

The cholesterol cycle

Cholesterol cycles between the liver and the blood,

BLOOD VESSEL Bad cholesterol performing vital functions. The process relies on a
PLAQUE Increased LDL in the balance between the two lipoproteins—HDL and
blood can cause cholesterol- LDL. If you have more LDL than HDL circulating,
filled plaques (atheromas) plaques can build up in arteries, which can raise
to build up, narrowing the blood pressure and lead to heart disease (see
arteries and increasing pp.212–15). High LDL levels can be due to diet,
blood pressure. If the plaque obesity, or genes.
ruptures, blood clots
can form, cutting off Liver removes
blood supply.

cholesterol from

body in the form

LIVER of bile salts

HDL removes Liver converts excess
cholesterol cholesterol into bile
from plaque
acids and recycles
or excretes them

PLAQUE LDL adds HOW DO
cholesterol STATINS WORK?
to plaque
Statin drugs lower
Good cholesterol cholesterol by slowing the
HDL particles transport excess liver’s cholesterol production.
cholesterol from the cells, Statins have many drawbacks,
blood, and plaques back to however, such as impeding
the liver. High HDL levels
mean that more cholesterol the body’s ability to use
is removed, reducing cholesterol to make
plaque formation. vitamin D.

Vitamins

A group of micronutrients found in different types of food,
vitamins are essential for our body’s growth, vitality, and
general well-being. Most of us can get the majority of the
vitamins we need from a healthy, balanced diet, but in
some cases, supplements can be useful.

What are vitamins? Fat-soluble

Vitamins are organic compounds that Some of the vitamins our
body needs dissolve in fat.
play an essential part in controlling our This means they are mainly
found in fatty foods, such as oily
body’s metabolic processes. Some, such fish, eggs, and dairy foods, rather
than fruit and vegetables. Fat-
as vitamin C and E, act as antioxidants, soluble vitamins aren’t absorbed
properly by the body if they are
which are thought to benefit the consumed without any fat, which means
that supplements of these vitamins taken
body by neutralizing excess free Vitamin without the right food may be less effective.
discovery
radicals (see pp.111). We need In the 1800s, doctors THE LIVER CAN STORE
only tiny amounts, but the realized that some ENOUGH VITAMIN A TO
LAST THE BODY 2 YEARS
lack of them can impair diseases were caused
not by germs, but by
body function and lead nutrient deficiencies.
to deficiency diseases. Animal experiments

Vitamins are classified using different diets
and supplements led
according to whether to the discovery of
they dissolve in fats these micronutrients.

or water.

Storage of vitamins Vitamin A Vitamin D
Needed for vision, Aids uptake of some
Our body can store fat-soluble vitamins in the growth, and development. minerals. Low levels can
liver, so we don’t need to eat them every day. Lack of vitamin A can lead lead to calcium deficiency
But because of this, if we take in too much, to poor vision or blindness, and poor bone health,
levels can build up in the body and become especially in children. including rickets in children.
toxic. Water-soluble vitamins can’t be stored
and any excess is excreted in urine. This means
we need to consume them more frequently.

Water-soluble vitamins
ingested often

Liver stockpile LIVER Liver stores Vitamin E Vitamin K
Fat-soluble vitamins fat-soluble An antioxidant. Needed to make
are stored in the same vitamins Protects cell membranes, blood-clotting agents. Low
cells that store fat, maintaining healthy skin consumption can lead to
mainly in the liver and eyes, and strengthens disorders in blood clotting,
but also elsewhere the immune system. bleeding, and bruising.
in the body.

FOOD FUNDAMENTALS 32 33
Vitamins
Chickpeas
WHERE IS KEY Leafy greens
VITAMIN F? Meat Broccoli
Poultry Avocado
The gaps in the vitamin Liver Tomatoes
Fish Bananas
alphabet are left by substances Oily fish Oranges
Tuna Strawberries
once thought to be vitamins, but Eggs Nuts
Egg yolk Peanuts
later reclassified. Some were found Milk Olive oil
Rice
not to be vital. Vitamin F, though Whole-wheat
bread
essential, was found to be a pair

Water-soluble of fatty acids that were better
classified as fats instead
Water-soluble vitamins
of vitamins.
are found in a wide variety

of foods, including fruit,

vegetables, and protein-rich foods.

Because they dissolve in water,

these vitamins can easily be lost in

food preparation, for example, through

the boiling of vegetables. The B

vitamins, together called the vitamin B

complex, are often grouped in supplements

and are sometimes found in the same foods.

Vitamin B1 Vitamin B2 Vitamin B3
Helps generate Important for Maintains the
energy and ensures muscles metabolism and healthy nervous system and brain,
and nerves function well. skin, eyes, and nervous the cardiovascular system
Low levels may cause system. Deficiency produces and blood, skin, and
headaches and irritability. weakness and anemia. metabolism.

Vitamin B5 Vitamin B6 Vitamin B7
Important for Involved in nerve Biotin. Needed for
metabolism and in the function, metabolism, and healthy bones and hair, and
production of neuro- making antibodies and fat metabolism. Lack of B7
transmitters, hormones, haemoglobin. Deficiency can cause dermatitis, muscle
and hemoglobin. can affect mental health. pain, and tongue swelling.

Vitamin B9 Vitamin B12 Vitamin C
Folic acid. Vital for Involved in An antioxidant.
healthy infant development. metabolism and making red Helps the growth and repair
Deficiency in an expectant blood cells. B12 deficiency of various tissues throughout
mother increases the risk can lead to a condition the body. Deficiency can lead
of spina bifida in her baby. called pernicious anemia. to poor wound healing.

Minerals

Like vitamins, we need minerals to function properly. Our bodies
require seven “macrominerals” in relatively large amounts, and only
minute levels of other “trace minerals.” Minerals occur naturally in
certain foods, so a balanced diet should provide sufficient mineral
intake but supplements may be necessary in cases of deficiency.

KEY Sodium Magnesium Potassium
Ready meals Regulates the amount Found in bones and Involved in muscle
Red meat of fluid in our bodies. Low inside all cells; needed for and nerve activity and fluid
Bacon sodium levels can cause a immune system, muscle, and balance. Low levels can
Fish wide range of effects from nerve health. Deficiency may cause muscle cramps and
Fish bones headaches to comas. lead to muscle problems, abnormal heart rhythms.
Shellfish vomiting, and heart issues.
Eggs
Egg yolk Chloride Minerals
Milk An important
Cheese component of stomach Minerals come from rocks or
Cereals acid. It is very rare to soil and dissolve in groundwater to
Whole grains lack this mineral. become charged particles, or ions.
Crisps
Leafy greens Plants absorb these ions into their
Lettuce tissues through their roots and the
Broccoli minerals reach us through the food
Tomatoes chain. “Macrominerals” are the
Bananas
Nuts minerals we need in the
Olives largest amounts.
Drinking water
Tea Sulfur Phosphorus Calcium
An essential part Needed for bone Essential for keeping
of many proteins, it is health, and involved in the our bones and teeth strong,
important for building process that releases energy and has many other roles in
new body tissues. from food. Very low levels the body, including nerve
can cause muscle weakness. and muscle functioning.

FOOD FUNDAMENTALS 34 35
Minerals

MINERAL DEFICIENCIES Tiredness YOU CAN GET
caused by ALL THE SELENIUM
Deficiencies in mineral intake can lack of iron YOU NEED EACH
cause various health problems. DAY FROM JUST
For example, long-term calcium Nausea can ONE OR TWO
deficiency can lead to reduced bone be caused BRAZIL NUTS
density and osteoporosis; lack of iron by lack of
may cause anemia, with weakness and
fatigue; and the early symptoms of magnesium
magnesium deficiency include nausea.
For each of these, dietary changes or
supplement use may be recommended.

Copper Fluoride
Needed by many Helps keep our bones
enzymes and for iron and teeth strong. Lack of
metabolism. Although fluoride may lead to an
very rare, deficiency increase in tooth decay.
can cause anemia.
Manganese, chromium,
Trace minerals molybdenum, nickel,
silicon, vanadium, cobalt
Minerals needed in only Also needed in
tiny amounts by the body are miniscule amounts.
called trace minerals. Despite the fact
that we need so little of them, trace Iodine
minerals are no less important than Important for normal thyroid
macrominerals. They include iron—a function. Deficiency can lead to
mineral often deficient in our diets. developmental problems and
physical or learning disabilities.

Selenium Iron Zinc
An antioxidant that Allows red blood Forms part of many
helps protect our cells from cells to carry oxygen, enzymes without which
stress. People dependent on and helps with energy our bodies can’t function
produce grown in selenium- production. Iron deficiency normally. Deficiency is linked
poor soil risk deficiency. anemia is quite common. to diarrhea and pneumonia.

Water DRINKING CAN YOU DRINK
WATER TOO MUCH WATER?
Up to 60 percent of our body weight is
water and it is needed to keep our organs If you drink too much too
functioning. While we can live without food quickly, cells swell as water
for several weeks, without rushes in. Swollen brain cells
water, death occurs in days, cause headaches, dizziness,
showing just how important it is.
and confusion. In severe
Hydration BRAIN cases, water poisoning

Getting enough water keeps our skin can lead to death.
plump and elastic, helps regulate body
temperature, and ensures our kidneys filter Dehydration
out waste. If the water concentration in
the blood is too high or too low, the body If more water is lost than taken in,
compensates by moving water into or out symptoms of light-headedness and
of our cells; both can be damaging. tiredness can start within hours. Thirst
is the body trying to correct the problem
A hydrated brain before it becomes severe. In extreme
Water is vital for the brain to function. cases, dehydration causes fits, brain
The balance between water and the damage, and death.
substances dissolved in it is important
for neurons to transmit signals effectively. Decreased attention and memory
If you become dehydrated, brain tissues shrink,
Moist eyes EYE and it takes more effort to carry out simple
To keep the eyes clean tasks. Attention, mood, memory, and reaction
and comfortable, they are time can be affected, and you may even
continually moistened with become more sensitive to pain.
tears, the major component
of which is water. EYE

Blood flows easily BLOOD VESSEL Dry eyes
Blood fluid (plasma) is 92 percent Dehydration slows tear
water. The liquid allows oxygen-carrying production which can leave
red blood cells, infection-fighting white the eyes feeling dry, irritated,
blood cells, and other vital components and gritty.
to flow easily to where they are needed.
Low blood pressure
If dehydration is severe, the water content
of your blood falls. Blood becomes thick and
viscous, making it difficult for your heart to
pump it around the body. This can lead to low
blood pressure, dizziness, and fainting.

Regulating hydration INTESTINES HOW MUCH DO I NEED?

We lose water mainly through urine, The amount of water you need varies
but some evaporates from the skin, or depending on the climate and what
is breathed out. The kidneys regulate you spend your time doing. Eight
water levels in the body and prevent glasses per day (2–3 quarts/liters) is
blood from becoming too concentrated frequently advised for moderately
or dilute. If water levels in your body active people in temperate climates,
tissues or cells fall, thirst is triggered. but this includes fluid from other
drinks and food. For young, healthy
Fluids outside SALTY people, the best thing to do is to
cells, such as SNACK listen to your body and drink when
blood, drop you feel thirsty! However, elderly
in volume Water people can become dehydrated
levels in without feeling thirsty, and so
Water cells drops must watch their water intake.
levels
in cells
don't fall

Salt Water WATER SOUP JUICE
drawn

out of cell FOOD FUNDAMENTALS
Water
Thirst due to Thirst due to Water aids digestion Constipation THE BODY STARTS
less water high salt intake In your stomach, acidic If you are dehydrated TO ABSORB
Sensors in your heart The salt concentration liquid, some of which is and food passes through WATER AS SOON
and arteries respond of blood fluid water, helps churn and the large intestine, your AS 5 MINUTES
when blood volume increases if excess salt digest your food. As the body absorbs water AFTER DRINKING
falls by 10 percent is consumed, causing processed food passes from it. This leaves
or more, and signal water to be drawn through your intestines, stools dry and hard,
thirst. Drinking tops from cells. If salt liquid keeps it moving easily. causing constipation.
up the liquid in your concentration rises
blood, increasing the by 1 to 2 percent, 36 37
volume of blood. thirst is triggered.

Pale urine BLADDER Concentrated urine
When you are well hydrated, your urine When you are dehydrated, the kidneys reduce the
is a pale straw color. If you drink a lot, a amount of water excreted, retaining water in the
blood. Urine gets darker in color due to substances
more dilute urine is produced. dissolved in the urine becoming more concentrated.

Convenience foods

With busy lives, many of us turn to ready-made WHAT MAKES
convenience foods. They are quick, easy, and tasty, JUNK FOOD
but not usually the healthiest option. So why are
convenience foods bad for us? And are there SO MOREISH?
healthier types we can choose?
Most junk food carefully
What are convenience foods? balances sweetness, salt, and

Convenience foods are preprepared or processed and include fat – designed to give our
prepackaged meals, cake mixes, snack foods, preprepared fruit and brains maximum pleasure
vegetables, frozen ingredients, and canned food. Companies that and keep us coming back
make and sell convenience foods usually focus on taste and shelf-life
rather than on nutritional value. By exploiting our evolved affinity for for more.
sweetness and our desire for quick, easy, tasty, high-calorie food,
they ensure products sell in high quantities. 50

High in refined carbs MILLION AMERICANS
The flour used is refined and ARE SERVED AT FAST
processed, removing most of the FOOD RESTAURANTS
fiber and micronutrients, but EVERY DAY
leaving the high calorie count.

High in fat
In addition to the oil in the
noodles themselves, the noodles
are often fried to dry them,
making them high in fat.

High in salt and sugar
Lots of salt and sugar is
added to make the bland
noodles tasty. This can
often exceed our daily
recommended amounts.

Instant noodles Low in fiber and protein
Just adding water to instant There is little fiber or
noodles provides a tasty, filling protein in instant noodles,
snack. However, they contain so despite their high calorie
few beneficial nutrients and count, they won’t satisfy
have been linked to increased you for long.
risk of obesity, diabetes, heart
disease, and strokes.

FOOD FUNDAMENTALS 38 39
Convenience foods

Modern eating habits Influence of takeouts
A study has shown that people who are exposed to
Ready-made food is all around us, from more takeouts at home, near work, or on their route
sandwich shops to takeout to fancy between the two, eat more takeouts and are more
restaurants, and this affects the way we likely to have a higher body mass index.
eat. When working hours are long and time
for food preparation and cooking is short, HOME
the appeal of instant, fast food rises.
However, there can be a trade-off between TAKEOUT
convenience foods and health.
One, or a few, takeouts Fewer takeouts
ROUTE BACK FROM WORK passed on the way home consumed

TAKEOUT HOME

ROUTE BACK FROM WORK Many takeouts passed More takeouts
on the way home consumed

History of GOOD CONVENIENCE FOODS CARROT AND
convenience foods CILANTRO SOUP
Not all convenience foods are unhealthy. Canned and
Convenience food is not new. Food frozen fruit and vegetables, or ready-made soups, are
can be preserved in many ways; good sources of nutrients and fiber—sometimes
frozen, canned, dehydrated, or by containing more vitamins and phytochemicals than
using additives. For some, this has their fresh ingredients (cooking tomatoes releases
improved nutrition, but for others it lycopene). But sugar and salt are often added to
has made it worse. improve the taste and preserve the soup for longer.

1810 Cans 1930s Flash-freezing Late 1960s 1970s Number
first used to invented, allowing Freezers and of women in work
preserve food foods to be frozen frozen prepared increases, leading to
for sailors on en masse and sold meals become a rise in the popularity
long voyages. to the public. mainstream. of preprepared meals.
1894 Corn flakes
1800 invented by Dr. John 1953–54 The first 2000
Harvey Kellogg. This ready-to-eat meals
was one of the first sold, in a metal tray 1967 Countertop 1979 The first
ready-to-eat cereals that could be heated microwave ovens chilled ready
to be mass produced. in an oven. introduced—but it meal, launched
would be 20 years by a supermarket
before they were in the UK.
common in the home.

Whole foods ARE WHOLE FOODS
THE SAME AS ORGANIC?
First introduced in the 1940s, the whole foods
movement is still increasing in popularity. Its focus Organic foods are crops
on eating unprocessed food is likely to increase fiber grown with natural fertilizers
and micronutrient intake, providing health benefits, or pesticides or animals reared
but it can be limiting if taken to the extreme. on organic feed—they are a

All natural type of whole food. But,
Raspberries have the highest whole foods are not
amount of omega-3 fatty acids in always organic.
any raw fruit. Also, 31⁄2 oz (100 g)
of raspberries contains more Nutrients and minerals
than one-quarter of your A whole-food diet is likely to contain a
daily needs of vitamin C. good variety of vitamins and minerals.
Raspberries are particularly high in
vitamins C, K, and manganese.

What are Antioxidants
whole foods? Whole foods such as raspberries
are rich in potentially beneficial
Whole foods are the opposite antioxidants (see pp.108–09).
of processed foods—they are in However, sometimes these can
their natural form, or processed as be added artificially to foods.
little as possible. They might include Fiber
fresh fruit, vegetables, meat, fish, whole grains, Plant foods that are less
nuts, and seeds. Some proponents argue whole processed tend to contain more
foods must also be organic, but there is little fiber. High fiber intake benefits
evidence for the health benefit of organic foods. weight loss and protects against
certain diseases (see pp.198–99).

Good fats
Whole foods don’t contain the
damaging trans fats common in
processed products and many
are high in beneficial
unsaturated fats.
Fewer additives
Whole foods are “as nature
intended,” without added flavorings
or preservatives. However, this means
they often don’t have as long a shelf
life as processed versions.

FOOD FUNDAMENTALS 40 41
Whole foods

Necessary processing

Not all foods are safe to eat without some degree VITAMIN C VITAMIN E

of processing. Some, especially meats, need to be

prepared or cooked to destroy toxins or kill dangerous

bacteria. Others, such as tomatoes, become more

nutritious when cooked (see p.55). Whole-food

proponents advise doing this processing

yourself, and keeping it to a minimum.

However, even a little chopping can VITAMIN A
affect the nutrition of foods.

Vitamin leakage
Coverings and peels such as apple
skin protect the fruit’s vitamins. Once
exposed to air, a small portion of the
vitamins (particularly vitamin C) react
with oxygen and are lost.

Whole-foods movement 1960s Consumers 2016 Whole-foods
in the western world (“clean-eating”)
Farmers and consumers in Europe start to take an interest diet comes back
in the 1920s started to seek out in food nutrition. into fashion.
foods grown without insecticides.
These natural foods were coined 1900 2016
“whole foods” by Frank Newman 1980s First Whole Foods
Turner, a British organic farmer, in 1940s Frank Newman Market opens in Texas,
1946. The “clean-eating” diet in the Turner was the first to selling exclusively
developed world has seen whole promote whole foods. organic, natural foods.
foods rise in popularity.

DRAWBACKS OF WHOLE FOODS 5 OZ
(150 G)
A strict whole-food diet can be expensive and OF STRAWBERRIES
time-consuming to prepare, and difficult to stick to PROVIDES YOU WITH
at social occasions or restaurants. It can also take a ALL OF THE VITAMIN C
while to get accustomed to the taste of fresh food YOU NEED IN A DAY
that contains less sugar and salt, if you are used to
processed food.

PREP TIME

Too much or too little?

Nutrients such as vitamins and minerals are good for us, but that

does not mean that more is better. Regularly consuming too much

of some vitamins, such as vitamin A, can be as dangerous as not

getting enough of them. PERCENTAGE OF PEOPLE WITH SYMPTOMS OF TOXICITY

100 50 0

RED BONES RRHEA Toxicity
FRACTU Nutrients in excess can become
DIA toxins. Excess magnesium may cause
diarrhea, for instance. Water-soluble
TOO MUCH vitamins don’t generally cause long-term
problems, as excess is excreted in urine,
but fat-soluble vitamins can build up and
cause serious damage. Too much vitamin
A, for example, can damage your bones.

At very high levels, nearly The maximum recommended amount AMOUNT OF NUTRIENT IN THE DIET
everyone experiences is where 2.5 percent of people
toxicity symptoms develop toxicity symptoms

JUST ENOUGH Everyone is different Most people
getting enough
Setting recommended minimum and maximum The yellow area of the graph
levels of a nutrient that works for a whole population is represents the recommended
problematic, because everyone's needs are different. A intake of a certain nutrient
minimum safe level is often set as the smallest amount that is healthy for most
needed by 97.5 percent of healthy people of a certain individuals.
age. This establishes a safe limit that applies to most
people. The remaining 2.5 percent of people who follow The minimum recommended
these recommendations will not get quite enough or amount is where 2.5 percent
get a little too much of a certain nutrient. of people develop deficiency

symptoms

TOO LITTLE At very low levels, everyone EBLEEDS Deficiency
experiences deficiency If you are deficient in any essential
symptoms nutrients, your body will not function
properly. You may experience symptoms,
PROBLEMS such as fatigue and headaches.
VISION Depending on which nutrient you are
NOS lacking, more serious symptoms, such
as vision problems (without enough
vitamin A) or nosebleeds (without
enough vitamin C) can occur.

100 50 0

PERCENTAGE OF PEOPLE WITH SYMPTOMS OF DEFICIENCY

FOOD FUNDAMENTALS 42 43
Too much or too little?

Food labeling THE DAILY NEEDS
OF CHILDREN AND
To make things simple, most governments turn your recommended ELDERLY PEOPLE ARE
daily need into a single guideline amount for use on packaging. NOT THE SAME AS
Some amounts are minimum amounts of essential nutrients, such THOSE FOR ADULTS
as minerals. Others are not targets, but guides to upper limits for
potentially unhealthy foods, such as salt, to encourage a healthy Nutrition claims
diet. Some countries highlight where nutrients in food are likely
to exceed your daily need if eaten in excess. Some foods make bold claims on the
packaging about what they contain (or
Amber means that this Green means that the amount Percentage of do not contain) and the health benefits
food contains a medium of sugar in this food is low your daily need they might have. But these claims are
tightly regulated, and the food must fit
amount of total fat Red means that this certain guidelines to make a specific
food contains a lot of claim. The regulations differ slightly
between countries, but some European
saturated fats Union (EU) examples are given below.

ENERGY FAT SATURATES SUGARS SALT
924KJ 0.7G
13G 5.9G 0.8G
220KCAL 12%
19% 30% <1%
11%

EACH GRILLED BURGER (94G) CONTAINS:

Traffic light system CLAIM RULING
The UK’s traffic light system Sugar-free
was developed by the Food If a food is labeled as sugar-free, it
Standards Authority and aims must contain less than 1 percent
to make choosing healthy sugar by weight.
food easier (in turn avoiding
NUTRITION FACTS long-term health effects). Low-fat Low-fat foods must contain
Exactly what “high” or “low” less than 3 percent fat by weight.
Serving size 1 cup (228g) means depends on the food
Servings per container 2 or drink and portion size,
but more green on a label
Calories 250 suggests a healthier food.
Calories from Fat 110
Labeling is not color coded
% DAILY VALUE High If they claim to be high in fiber,
Recommended daily values in fiber foods must have at least 6 percent
Total Fat 12g 18% for nutrients such as fat and fiber by weight.
Saturated Fat 3g 15% salt are maximums, not targets
Trans Fat 3g Percentages of daily need Source of A food can be called a source of
10% Many countries, including the vitamin D vitamin D if it provides 15 percent
Cholesterol 30mg 20% US, have food labels that show of your daily need per 31⁄2oz (100g).
Sodium 470mg 10% quantities of each nutrient as a
Total Carbohydrate 31g percentage of your daily need.
They also show the total
Dietary Fiber 0g 0% calories per serving. Quantities Reduced- Reduced-fat products must
Sugars 5g of certain micronutrients (such fat contain 30 percent less fat than
Protein 5g 4% as iron) must also be shown. a similar product. This does not
Vitamin A 2% mean it is necessarily low in fat
Vitamin C 20% compared to other foods!
Calcium 4%
Iron

MACARONI AND CHEESE



STORING
AND COOKING

How fresh SUNLIGHT
is fresh?
WRINKLING
Freshness has become an important concept
in evaluating the quality and desirability of Post-harvest, a
food. But what does “fresh” actually mean? combination of a
What are the factors influencing freshness loss of water supply,
and how do food labels help us to assess the sunlight, and wind
freshness of food? can cause wrinkling

Decreasing freshness From ripe to rotten
A complex combination of physical
While some fruit and vegetables and organic processes operates
only reach peak ripeness or on a piece of fruit to affect its
desirability after harvesting, most freshness and determine the rate
foods will start to lose flavor and at which it declines.

nutritional value from the moment

they are harvested or butchered.

This is the point at which a number SHOULD I
of processes that make foods spoil FREEZE FOOD AS
begin. These include the release of SOON AS I BUY IT?
destructive enzymes; the natural

breakdown processes, such as One common myth is that BRUISING
oxidation, that degrade nutrients; food must be frozen on the day
and the growth of microbes as
defense mechanisms in the food’s of purchase. In fact, you can
cells start to stall. In some fruit and freeze food at any time up

vegetables, natural metabolic to the use-by date on

and physiological processes may the label.
actually accelerate after harvesting.

Time limit for freshness? Harvest Air freight
To avoid damage and More perishable foods, such
Some plant foods can remain fresh increase shelf life, most as berries, are more likely
for remarkably long periods, if fruit and vegetables are to be air-freighted to
stored correctly. Potatoes can stay harvested by hand. consumer countries.
fresh for three months in a cool,
dark place. Pears and apples can 0 1-3
be stored for up to a year in special DAYS DAYS
atmospherically controlled facilities.
1-4
Food’s journey FREIGHT TIMELINE Refrigerated ships WEEKS
Produce such as fruit and vegetables grown in the Refrigerated ships can provide
southern hemisphere will pass through many highly controlled temperatures to
stages on its journey to markets in the US. keep produce as fresh as possible.

STORING AND COOKING 46 47
How fresh is fresh?

Bacteria may feed on, BACTERIA Loss of nutrients
degrade, and digest
Nutrients are lost at an accelerating rate as a food’s
exposed parts of food freshness declines. They are particularly affected
by oxidation, heat, sunlight, dehydration, and
enzymes. Vitamin C can be extremely vulnerable
to degradation over time, although this varies
between foods. Chilling and freezing are especially
helpful in delaying or preventing nutrient loss.

Vitamin C

Larvae feed on apples, Effects of chilling
affecting their freshness Broccoli stored for
and sometimes causing seven days at 32ºF
them to drop too early (0ºC) can retain
most of its vitamin C,
compared to 44 0ºC/32ºF 20ºC/68ºF
percent when stored
APPLE SAWFLY LARVA at 68ºF (20ºC). MEANING

ENZYMATIC BREAKDOWN LABEL TYPE

Oxygen seeps Sell by There is no legal requirement to show this date;
into apple it is used more to help retailers manage stock.

Display until Similar to “Sell by,” this label is used by retailers
to help manage their stock levels.

Best before The “Best before” date refers to food quality,
rather than safety.

CELL Enzyme Use by In some countries, this label has legal force.
reacts with Food is not safe for use after this date.
Enzyme oxygen
released Brown color produced by Types of date labels
from cell melanins, brown pigments, Date labels on food are supposed
created by reactions between to inform the consumer, but can
enzymes, tannins (type of acid), be confusing.
and oxygen

Retailer 45
Advanced stock management
techniques allow retailers to PERCENT OF ALL
minimize wastage and guarantee THE FRUIT AND
appropriate stock levels. VEGETABLES
PRODUCED
1-3 1-3 0-7 ARE WASTED
DAYS DAYS DAYS

Distribution center Consumer
Handling is kept to a The end goal is to ensure
minimum and conditions that the produce reaches
continue to be tightly the consumer at or before
controlled. its peak ripeness.

Preservation SPICES AND HERBS
WERE USED AS
The very things that make food nutritious PRESERVATIVES BY
also make it vulnerable to contamination ANCIENT CIVILIZATIONS
and degradation, so preserving food has
always been a key concern of food science
and cultures since ancient times.

Types of preservation Chilling and freezing Chemical
Reducing temperature Artificial preservative
Natural processes, including decreases the rate of chemicals, such as nitrates,
microbial growth, oxidation, biochemical reactions. are commonly used in foods
heat and light, and the action of Freezing suspends them. such as meats (see pp.74–75).
enzymes can contaminate foods Drying Canning
or degrade them by breaking down Water is necessary for most In addition to sealing food,
their key components. The rate biochemical activity, so canning also involves
of the biochemical reactions that removing moisture can extreme heat treatment
drive these processes depends on prevent microbial growth. to kill off any microbes.
favorable conditions, so altering Salting Smoking
these in different ways can help to Increasing the concentration Smoking infuses foods with
preserve foods. Some preservation of salts in food kills most a variety of antimicrobial,
methods, such as drying, have microbes by dehydrating antioxidant, and acidifying
been used for tens of thousands them. compounds.
of years. Artificial chemical Pickling Storing
preservatives are common Making food more acidic Storing food in cool, dark
today—but their implications can kill many microbes but conditions prolongs its shelf life,
for our health remain uncertain. will also affect the food’s as will reducing exposure to
taste and characteristics. oxygen and ambient microbes.

How nutrients degrade NUTRIENT LEVEL OF STABILITY NUTRIENT LEVEL OF STABILITY

Some categories of nutrients, such Proteins, Relatively stable Vitamin B1 Highly unstable; sensitive
as vitamins and antioxidants, are carbohydrates (thiamine) to air, light, and heat
reactive since they are composed of
fragile molecules. Such vulnerable Fat Can become rancid Vitamin B2 Sensitive to light and heat
molecules will degrade naturally Vitamin A (see p.74), particularly (riboflavin) Relatively stable
over time, a process that speeds up at higher temperatures Vitamins
greatly with heat, physical damage, B3 (niacin),
exposure to sunlight, and exposure Sensitive to air, light, B7 (biotin)
to oxygen – the last of which and heat
generates destructive free radicals
(see p.111). Different nutrients are Vitamin C Highly unstable; sensitive Vitamin B9 Highly unstable; sensitive
more sensitive to certain threats to air, light, and heat (folic acid) to air, light, and heat
than others.

Vitamin D Somewhat sensitive Carotenes Sensitive to air, light,
to air, light, and heat and heat