NOTA SLAID

• In 1945, it was discovered that the amino acid tryptophan also could
cure pellagra

• Tryptophan is a precursor of niacin
• It can be converted into niacin in the body’s cells
• However, this conversion requires the presence of:

• Thiamin (B1), Pyridoxine (B6), Riboflavin (B2)

173

Functions

• Niacin coenzyme, NAD and NADP play key roles in oxidation-
reduction reactions

• The coenzymes participate in numerous metabolic reactions –
especially metabolism of glucose, fat and alcohol

174

NAD in Energy Metabolism

RNI for Malaysia (2017)

Age group 0 – 5 months mg Niacin Equivalent (NE)/day
Infant 6 – 11 months
2
Children 1 – 3 years
4 – 6 years 4
Adolescent 7 – 9 years
≥19 years (Male) 10 – 18 years 6 The conversion factor is 60 mg
≥19 years (Female) 8 tryptophan to 1 mg niacin, which is

Pregnancy referred to as 1 niacin equivalent
Lactation 12 (NE)

16

16
14

18

17

Food Sources

• Niacin is unique - the body can make it from the amino acid
tryptophan as well as obtain form foods

• Food with rich sources of niacin- mushrooms, wheat bran, meat , fish,
poultry, legumes, enriched and whole grains and peanuts

• Protein rich foods also are good sources of niacin because they
provide tryptophan

• Heat resistant- withstand reasonable cooking times

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Biosynthesis

• The liver can synthesize
niacin from the
essential amino acid
tryptophan

The conversion factor is 60 mg tryptophan
to 1 mg niacin, which is referred to as 1
niacin equivalent (NE)

• 60 mg of tryptophan make 1 mg of niacin

• Requires the presence of:

• Thiamin (B1), Pyridoxine (B6), Riboflavin (B2)

Toxicity

• No toxicity - from food intake Niacin flush

• Excess supplements (and overly fortified foods):

• Reddish colouring of the face, arms, and chest
• Nausea, vomiting
• Heartburn
• Liver toxicity
• Raised blood glucose levels

Tolerable Upper Intake levels

Deficiency

• Pellagra • Symptoms

• Means “rough or painful • Dermatitis
skin”
• esp. on areas of skin exposed to the sun
• disease of the 4 Ds
• Diarrhea
• Dementia
• Death
• Poor appetite
• Weight loss
• Weakness



Pantothenic Acid (B5)

• Pantothenic acid is widely available
• Part of Coenzyme A, then makes acetyl CoA

Functions

• In its coenzyme form, it helps release energy from carbohydrates, fats
and proteins

• helps the body convert food (carbohydrates) into fuel (glucose), which the
body uses to produce energy.

• helps the body use fats and protein.

Pantothenic Acid and Energy Metabolism

• In addition, pantothenic acid is critical to the manufacture of

• red blood cells,
• as well as sex and stress-related hormones produced in the adrenal glands.

• It is also important in maintaining a healthy digestive tract
• It helps the body use other vitamins, particularly riboflavin (B2)
• Required for other vitamin syntheses

• which are vitamin A and vitamin D

Sources

• Widespread in the foods
• Common sources: meat, milk and many vegetables
• Rich sources: mushrooms, avocados, peanuts, egg yolks, yeast ,

broccoli and soy milk, whole grain, organ meats

• Readily destroyed by the freezing, canning and refining processes
• Stable in moist heat and neutral pH
• Relatively unstable in dry heat, acid and alkali
• Food that undergoes dry heat during processing are relatively poor

sources of pantothenic acid

RNI for Malaysia (2017)

Age group 0 – 5 months mg/day
Infant 6 – 11 months 1.7
1.6
Children 1 – 3 years 2.0
4 – 6 years 3.0
≥10 years 7 – 9 years 4.0
Pregnancy 5.0
Lactation 6.0
7.0

Toxicity

• High intakes have not caused adverse effects
• No known toxicity – no upper level has been set

Deficiency

• Deficiency is very rare • Symptoms include:
• Might occur in alcoholism
• Fatigue
• Nausea
• Vomiting
• Numbness
• Muscle cramps
• Difficulty walking

Pyridoxine (B6)

• The primary coenzyme is pyridoxal phosphate (PLP)

• Vitamin B6 is converted to PLP by adding a phosphate group (PO4) to its
hydroxyl group

Functions

• (PLP) is involved in amino acid metabolism

• PLP plays a key role in transamination reactions that transfer an amino groups
from an amino acid to a keto acid and produce non-essential amino acids

• PLP is also involved as a cofactor in the decarboxylation of amino acids to yield amines

• Many enzymes are PLP dependent because they are needed to
transform amino acids into other resources.

Transamination of non-essential amino acid

• In the muscle, PLP functions as a coenzyme of glycogen
phosphorylase

• facilitate the breakdown of glycogen and results in the formation of glucose-
1-phosphate.

• Vitamin B6 also acts as a regulator of actions of steroid hormones,
calcitrol, retinol and retinoic acid, and the thyroid hormones

• PLP releases the hormone-receptor-complex from tight nuclear binding, and
terminates hormone actions

Sources

• Richest sources: meat, fish and poultry
• Others: Fortified breakfast cereals, fruit

and vegetables (carrots, potatoes,
spinach, bananas and avocados

Banana 0.4mg/100g Jackfruit 0.3mg/100g
Durian 0.3mg/100g

• Unstable to heat and processing
• Vitamin B6 taken without food is almost completely absorbed, even

when taken in mega-doses

RNI for Malaysia (2017)

Age group 0 – 5 months mg/day
Infant 6 – 11 months 0.1
0.3
Children 1 – 3 years 0.5
4 – 6 years 0.6
Adolescent (Male) 7 – 9 years 1.0
Adolescent (Female) 10 – 18 years 1.3
10 – 18 years 1.2
Adults 19 – 50 years 1.3
Adults (Male) >50 years 1.7
Adults (Female) >50 years 1.5
1.9
Pregnancy 2.0
Lactation

Tolerable Upper Level

• Upper Level : 100 mg/day, based on the risk of developing nerve
damage

Toxicity

• From excess supplement intake.

• It attaches to enzymes in muscle and other tissue & remains in body.

• Intake of 2000 mg/day or more for 2 or more months can lead to
irreversible nerve damage

• Symptoms of toxicity: walking difficulties, hand and foot numbness

Deficiency

• Symptoms

• Stomatitis (inflammation of the mucous lining of any of the structures in the
mouth)

• Glossitis (inflammation or infection of the tongue)
• Dermatitis (inflammation of the skin)
• Neurological symptoms - depression, confusion and convulsions

• Microcytic hypochromic anemia

• low levels of red blood cells that are both smaller and paler than normal

Biotin (B7)

• Biotin’s discovery was linked to “Egg
white injury”

• Sulfur-containing vitamin
• In food, biotin is found both free

and bound to proteins (biocytin)

Functions

• It is important in energy metabolism
• Biotin is a coenzyme that participates in carboxylation reactions

carboxylation: introduction of a carboxyl group into a
compound or molecule

• Biotin assists in the addition of CO2 to other compounds

• It promotes the synthesis of glucose, fatty acids and DNA, while helping to
break down certain amino acids

• Biotin also binds to the protein that help DNA fold in the cell nucleus



Sources

• Widely distributed in foods
• Good sources: Cauliflower, soybeans, whole grains, egg yolks,

peanuts, and legumes, cheese, liver
• Bacteria in the large intestine synthesize biotin



Biotin Needs

• Not included in RNI (2017)
• 30 μg biotin/day (adults)
• Biotin does not appear to be toxic at high doses- no upper level has

been set

Toxicity

• No known toxicity

Deficiency

• Deficiencies are rare. • Vomiting
• Depression
• Symptoms: • Muscle pain and weakness
• Poor growth
• Scaly rash around the eyes, nose • Hair loss
and mouth • Decreased appetite

• Neurological impairment
• Nausea





• Biotin deficiency resulted from:

• Use of anticonvulsant (antiepileptic) medications
• Malabsorption- severe intestinal diseases
• Eating raw egg whites over a long period

• The avidin in it binds biotin => deficiency symptoms

• Infants born with biotinidase deficiency
• Alcoholic

• If not treated, biotin deficiency causes changes in blood pH that can lead to coma
and death

Folate (B9)

• Folate - the natural form of B9 in foods
• Folic acid - synthetic form, added to foods and in supplements
• Active form: 5-methyltetrahydrofolate (5-MTHF)

• Folate consists of 3 parts:

• pteridine, para-aminobenzioc acid (PABA), and 1 or more molecules of the

amino acid glutamic acid

Pteridine

H2N N N p-Aminobenzoic acid Glutamic acid

N N CH2 NH O COOH
OH C NH CH

CH2
CH2
COOH

• Most folate in foods = polyglutamate form