Main function

Main deficiency symptoms


(Vitamin A)

Maintain healthy surface linings of the eyes, the respiratory, urinary, and intestinal tracts, the skin and mucous membranes; night vision; bone development; antioxidant.

Bitot’s spots, xerophthalmia, corneal ulcers, scarring of the cornea and blindness; impaired dark adaptation. High incidence of respiratory illnesses and diarrhoea; increased mortality


(Vitamin B-1)

Carbohydrate metabolism, coenzyme for synthesis of nucleic acids

Polyneuropathy (PN), diminished sensation and weakness in the extremities. Muscle pain and tenderness, seizures (severe deficiency). Signs of congestive heart failure


(Vitamin B-3)

Metabolism of carbohydrates, fats and proteins and synthesis of fatty acids and cholesterol

Dermatitis, diarrhoea, bright red tongue, vomiting, and diarrhoea, apathy and fatigue


(Vitamin B-6)

Coenzymes that catalyse gluconeogenesis, synthesis of neurotransmitters, heme, nucleic acids, conversion of homocysteine to cysteine, production of lymphocytes and IL-2

PN, irritability, confusion, seizures in severe deficiency. Inflammation of the tongue, sores or ulcers of the mouth, angular stomatitis and anaemia.

Folic acid

(Vitamin B-9)

Metabolism of nucleic acids and amino acids, synthesis of DNA, RNA, conversion of homocysteine to methionine.

Megaloblastic anaemia and symptoms of anaemia (fatigue, weakness, and shortness of breath)


(Vitamin B-12)

Amino acid metabolism, methylation of a number of sites in DNA and RNA, production of energy from fats and proteins, haemoglobin synthesis.

Megaloblastic anaemia, PN, difficulty walking, mood changes, tongue soreness, appetite loss, and constipation

Ascorbic acid

(Vitamin C)

Synthesis of collagen, synthesis of carnitine which is essential for thetransport of fat into mitochondria for theproduction of energy, metabolism of cholesterol to bile acids. Antioxidant, enhance chemotaxis and phagocytosis

Bleeding and bruising easily hair and tooth loss, and joint pain and swelling, fatigue


Vitamin D)

Absorption of calcium and hardening of bones. DNA synthesis and transcription of genes, cellular differentiation, modulates immune cells e.g. dendritic cells and macrophages

Rickets, muscle weakness and pain,

frequent bacterial infections


(Vitamin E)

Antioxidant, maintain integrity of cell membranes, affect the expression and activities of enzymes in immune and inflammatory cells

PN and muscle weakness