Table 2 Vitamins and associated deficiency diseases
VitaminMetabolic role and coenzyme functionDeficiency disease
Fat-soluble
A (Retinol)Vision; cell proliferation and division; glycoprotein synthesisNight blindness; xerophthalamia
D (Cholecalciferol)Bone growth calcium homoeostasis; immune regulationRickets (children) and osteomalacia (adults) – defective bone development, bones are soft and weak
E (Tocopherol)Protection from reactive oxygen speciesHaemolytic anaemia
K (Phylloquinone)Cofactor for γ-glutamyl carboxylase. Synthesis of coagulation factorsCoagulation defect – excessive bleeding
Water-soluble
B1 (Thiamine)Carbohydrate metabolismBeriberi – accumulation of lactate and pyruvate causes peripheral vasodilation, oedema and heart failure
B2 (Riboflavin)Role in redox reactionsEye and skin inflammation disorders (particularly at corners of mouth)
B3 (Niacin)Role in enzyme hydrogen donors/acceptors in redox reactions involved in oxidative phosphorylation and fatty acid synthesisPellagra (rare) – dermatitis, dementia and diarrhoea
B5 (Pantothenic acid)Part of coenzyme A and acyl carrier protein (ACP) – role in citric acid cycle and lipid synthesisN/A
B6 (Pyridoxine)Amino acid metabolism: coenzyme pyridoxal 5′-phosphate. Also associated with glycogen phosphorylaseWeakness, peripheral neuropathy, Dermatitis
B7 (Biotin)Coenzyme for carboxylase enzymes involved in fatty acid, amino acid metabolism and citric acid cycleDermatitis
B9 (Folic acid)Tetrahydrofolate plays a role in one carbon transfer reactions in DNA synthesisMegaloblastic anaemia and neural tube defects in pregnancy
B12 (Cyanocobalamin)Methionine and proprionate metabolism: cofactor in enzymes methionine synthase and methylmalonyl-coA mutaseMegaloblastic anaemia and neurological dysfunction
C (ascorbic acid)Antioxidant. Required by hydroxylase enzymes for collagen synthesis – conversion of proline into hydroxyproline. Protein metabolismScurvy – poor wound healing, haemorrhage, swollen gums, weakness, ‘corkscrew’ hair
  • Each vitamin’s name often refers to several related compounds (e.g. Vitamin A refers to retinol, retinal, retinoic acid). Only one biomolecule is named here for simplicity. Dietary sources of vitamins and values for the recommended daily intake are widely available in other texts (see ‘Further reading’ section).