Vitamins & Minerals
Vitamins are organic micronutrients required in small amounts for normal metabolism. They function primarily as coenzymes or their precursors, and cannot be synthesized in adequate amounts by the body.
Fat-Soluble Vitamins (A, D, E, K)
Stored in liver and adipose tissue. Risk of toxicity with excess intake. Absorbed with dietary fats.
- Vitamin A (Retinol): Night vision (rhodopsin), cell differentiation, immune function. Deficiency: Night blindness, xerophthalmia. Toxicity: Teratogenicity.
- Vitamin D (Calciferol): Calcium & phosphorus homeostasis. Synthesized in skin (UV light). Activated in liver → kidney (1,25-dihydroxycholecalciferol = calcitriol). Deficiency: Rickets (children), Osteomalacia (adults).
- Vitamin E (Tocopherol): Antioxidant; protects cell membranes from oxidation. Deficiency: Hemolytic anemia, neuropathy.
- Vitamin K (Phylloquinone): Required for γ-carboxylation of clotting factors (II, VII, IX, X) and proteins C and S. Warfarin antagonizes Vit K. Deficiency: Bleeding tendency.
Water-Soluble Vitamins (B-complex & C)
Not stored; excess excreted in urine (except B12). Deficiency develops more rapidly.
- B1 (Thiamine) → TPP: Oxidative decarboxylation (PDH, α-KGDH). Deficiency: Beriberi (wet=cardiac, dry=neurological), Wernicke-Korsakoff (alcoholics).
- B2 (Riboflavin) → FAD/FMN: Electron carriers in oxidative phosphorylation.
- B3 (Niacin) → NAD+/NADP+: Most important coenzyme. Deficiency: Pellagra (3Ds: Dermatitis, Diarrhea, Dementia). Tryptophan is precursor.
- B5 (Pantothenic acid) → CoA: Fatty acid metabolism.
- B6 (Pyridoxine) → PLP: Transamination, decarboxylation. Deficiency: Peripheral neuropathy, sideroblastic anemia.
- B7 (Biotin): Carboxylation reactions (ACC, Pyruvate carboxylase). Avidin in raw egg whites binds biotin → deficiency.
- B9 (Folate → THF): One-carbon transfers; nucleotide synthesis. Deficiency: Megaloblastic anemia, Neural tube defects (NTDs).
- B12 (Cobalamin): Requires intrinsic factor (IF) for absorption. Cofactor for methionine synthase & methylmalonyl-CoA mutase. Deficiency: Megaloblastic anemia + subacute combined degeneration of spinal cord.
- Vitamin C (Ascorbic acid): Antioxidant; collagen synthesis (hydroxylation of Pro & Lys). Deficiency: Scurvy (bleeding gums, perifollicular hemorrhages, poor wound healing).
Essential Minerals
- Iron: Component of heme (Hb, Mb, cytochromes). Deficiency: Microcytic hypochromic anemia. Absorbed as Fe²⁺; haem-iron better absorbed.
- Calcium: Bone/teeth, muscle contraction, blood clotting, nerve function.
- Iodine: Thyroid hormone synthesis. Deficiency: Goiter, Cretinism.
- Zinc: Metalloenzyme cofactor (carbonic anhydrase, carboxypeptidase). Wound healing.
- Selenium: Antioxidant; part of glutathione peroxidase.