Micronutrients: Vitamins, Minerals and Water
What this domain tests
Vitamins and minerals are needed in small amounts but do not supply energy. Water is the most abundant body component and is essential for transport, temperature regulation and excretion. The exam tests classification, functions, deficiency diseases and sources.
Core rules
- Fat-soluble vitamins are A, D, E and K; they are stored in the body and can be toxic in excess.
- Water-soluble vitamins are the B complex and vitamin C; excess is generally excreted, so regular intake is needed.
- Vitamin A deficiency causes night blindness and xerophthalmia; thiamine deficiency causes beri-beri; niacin deficiency causes pellagra; vitamin C deficiency causes scurvy; vitamin D deficiency causes rickets in children and osteomalacia in adults.
- Iron deficiency causes microcytic anaemia; iodine deficiency causes goitre and cretinism; calcium and vitamin D are needed for bone health.
- Water requirement is influenced by climate, activity, fever and diet; dehydration impairs performance and can be fatal.
Worked example
A child has difficulty seeing in dim light, dry conjunctiva and Bitot’s spots. Reasoning: these are clinical signs of vitamin A deficiency, not simply “weak eyes”. The plan includes vitamin A supplementation as per national guidance, dietary sources such as dark green leafy vegetables, carrot, papaya and liver, and treatment of infection. Giving only carrots without supplementation may be too slow in severe deficiency.
Traps that cost marks
- Calling vitamin C fat-soluble.
- Mixing up pellagra (niacin) with beri-beri (thiamine).
- Saying minerals supply energy.
- Ignoring that fat-soluble vitamins can accumulate and cause toxicity.