Vitamins, Minerals and Nutrition: Deficiency Diseases and Dietary Requirements
What this domain tests
Nutrition questions test fat-soluble and water-soluble vitamins, specific deficiency diseases, mineral functions, and dietary requirement terms.
Core rules
- Fat-soluble vitamins A, D, E, K are absorbed with lipids; malabsorption causes multiple deficiencies. Water-soluble B complex and C are not stored in large amounts, so deficiencies appear faster.
- Vitamin A deficiency causes night blindness and xerophthalmia. Vitamin D deficiency causes rickets in children and osteomalacia in adults. Vitamin E deficiency causes hemolysis. Vitamin K deficiency causes bleeding because gamma-carboxylation of factors II, VII, IX, X is impaired.
- B1 deficiency causes beriberi and Wernicke-Korsakoff syndrome; B3 deficiency causes pellagra (dermatitis, diarrhea, dementia); B9 deficiency causes megaloblastic anemia; B12 deficiency causes megaloblastic anemia with neurological signs; C deficiency causes scurvy.
- Minerals: calcium and phosphate for bone; iron for hemoglobin; iodine for thyroid hormone; zinc for many enzymes.
- Marasmus is severe energy-protein deficiency with wasting; kwashiorkor is protein deficiency with edema.
Worked example
A patient on prolonged broad-spectrum antibiotics develops bruising and prolonged prothrombin time. Gut bacteria normally make vitamin K, and antibiotics reduce this supply. Vitamin K is needed for gamma-carboxylation of glutamate residues in clotting factors II, VII, IX, and X. Giving vitamin K corrects the coagulation defect; giving vitamin C would not, because scurvy affects collagen hydroxylation, not these clotting factors.
Traps
Vitamin D is not calcitonin; it increases calcium absorption. B12 deficiency can cause neurological damage even before anemia. Folate can mask B12 anemia while neuropathy progresses. Fat malabsorption affects vitamins A, D, E, and K together.