Vitamins and Minerals: Sources, Functions and Deficiency Diseases
Fat-soluble vitamins (A, D, E, K)
A (retinol, β-carotene) for vision, epithelium and immunity; deficiency causes night blindness, Bitot's spots, xerophthalmia and keratomalacia. D for calcium absorption; deficiency causes rickets in children and osteomalacia in adults. E is a membrane antioxidant; deficiency causes haemolysis. K is needed for clotting factors II, VII, IX and X; deficiency causes bleeding, including haemorrhagic disease of the newborn.
Water-soluble vitamins (B complex, C)
Thiamine (B1) - beriberi, Wernicke encephalopathy. Riboflavin (B2) - angular stomatitis, cheilosis. Niacin (B3) - pellagra with dermatitis, diarrhoea and dementia; 60 mg dietary tryptophan equals 1 mg niacin equivalent. B6 - amino acid metabolism. B12 - pernicious and megaloblastic anaemia with neurological damage; found only in animal foods. Folate - megaloblastic anaemia and neural tube defects. Vitamin C - collagen synthesis, antioxidant, enhances non-haem iron absorption; deficiency causes scurvy with bleeding gums, perifollicular haemorrhage and poor wound healing.
Minerals
Calcium - bone, clotting, muscle contraction; deficiency gives rickets, osteomalacia, tetany. Iron - haemoglobin; deficiency gives microcytic hypochromic anaemia. Iodine - thyroxine; deficiency gives goitre and cretinism. Zinc - growth, wound healing, taste acuity. Fluoride - prevents dental caries in optimal amounts.
Worked example
A child presents with bleeding gums, loose teeth, easy bruising and slow-healing wounds. Reasoning: these are all collagen-synthesis failures, so the diagnosis is scurvy from vitamin C deficiency, corrected with citrus fruit, amla and guava. Vitamin K deficiency also bleeds, but it presents as prolonged clotting and bruising, not as the gum and wound-healing picture the question describes.
Traps that cost marks
Water-soluble vitamins are not stored appreciably, so deficiency develops faster. Vitamins A and D are toxic in excess. Iodine deficiency is prevented by iodised salt, not by extra protein. Anaemia is not automatically iron deficiency - folate and B12 also cause it.