Vitamins
Vitamins are organic compounds essential for normal metabolism, growth, and overall physiological functioning. Since the human body cannot synthesise most vitamins, they must be obtained through diet or supplements.
A total of 13 vitamins are recognised, classified based on solubility, which directly influences their absorption, storage, and deficiency patterns.
Classification of Vitamins
| Basis | Fat-Soluble Vitamins | Water-Soluble Vitamins |
| Solubility | Dissolve in fats | Dissolve in water |
| Storage | Stored in liver & adipose tissue | Not stored; excess excreted in urine |
| Toxicity Risk | High (accumulation possible) | Low (regular intake required) |
| Examples | A, D, E, K | B-complex (B1–B12), C |
Fat-Soluble Vitamins (A, D, E, K)
| Vitamin | Functions | Sources | Deficiency / Disorders |
| A (Retinol) | Vision, immune function, reproduction, regulation of cell growth | Liver, fish oils, milk, eggs, leafy green vegetables, orange & yellow vegetables (carrots, sweet potatoes) | Nyctalopia (night blindness), Xerophthalmia (dry eyes), dry skin and hair |
| D (Calciferol) | Helps absorb calcium and phosphorus (critical for bone health), controls infections, reduces inflammation | Sunlight exposure, fortified milk, fatty fish (salmon, mackerel), egg yolks | Rickets (children) – soft bones & skeletal deformities; Osteomalacia (adults) – weak, softened bones |
| E (Tocopherol) | Acts as an antioxidant, prevents clot formation in heart arteries | Nuts, seeds, vegetable oils, green leafy vegetables, pumpkin, avocados, mangoes, wheat germ oil | Retinopathy, Peripheral neuropathy, Ataxia, decreased immune function |
| Vitamin K (Phylloquinone) | Blood clotting, bone health | Green leafy vegetables, fish, meat, dairy products, fermented food | Bleeding diathesis (easy bleeding/bruising), haemorrhaging, osteopenia/osteoporosis |
Water-Soluble Vitamins
| Vitamin | Functions | Sources | Deficiency / Disorders |
| Vitamin B1 (Thiamine) | Energy metabolism, cell growth, proper brain function | Whole grains, pork, fish, legumes, seeds, nuts | Beriberi (cardiovascular & nervous system weakness), Wernicke-Korsakoff syndrome (memory disorder) |
| Vitamin B2 (Riboflavin) | Cell growth, energy production, fat metabolism | Dairy products, eggs, green leafy vegetables, lean meats, nuts | Ariboflavinosis (skin disorders, cracked lips, inflamed tongue, hair loss, eye issues, liver & nervous system degeneration) |
| Vitamin B3 (Niacin) | Converts nutrients into energy, increases good cholesterol, DNA repair, antioxidant role | Meat, fish, poultry, whole grains, nuts | Pellagra – 3Ds: Dermatitis, Diarrhoea, Dementia (can lead to death) |
| Vitamin B5 (Pantothenic Acid) | Synthesis of Coenzyme A (CoA) and acyl carrier protein (fat metabolism) | Almost all foods (especially whole grains, eggs, meat, legumes) | Fatigue, irritability, numbness, muscle cramps |
| Vitamin B6 (Pyridoxine) | RBC production, brain function, metabolism of proteins, carbohydrates, fats | Fish, beef liver, potatoes, non-citrus fruits | Microcytic anaemia, dermatitis, depression, confusion, weak immunity |
| Vitamin B7 (Biotin) | Breakdown of fats, carbohydrates, proteins; gene regulation | Eggs, almonds, nuts, legumes, whole grains, salmon, avocados | Hair loss, dermatitis, brittle nails |
| Vitamin B9 (Folic Acid) | DNA & RNA synthesis, RBC formation, protein metabolism, fetal development | Leafy green vegetables, fruits, fortified foods | Megaloblastic anaemia, neural tube defects, fatigue, pale skin |
| Vitamin B12 (Cobalamin) | Nerve & brain function, RBC and DNA synthesis | Meat, fish, poultry, dairy products, fortified cereals | Megaloblastic anaemia, Pernicious anaemia, neurological disorders |
| Vitamin C (Ascorbic Acid) | Antioxidant, collagen synthesis, immunity, enhances iron absorption, wound healing | Citrus fruits, strawberries, bell peppers, broccoli, Brussels sprouts | Scurvy (bleeding gums, poor healing), iron deficiency anaemia |
Important Concepts
- Vitamin D acts both as a nutrient and a hormone.
- Vitamin K is partially synthesised by gut bacteria.
- Some B vitamins (e.g., Riboflavin) are also produced in small amounts by gut bacteria but are insufficient.
Role of Antioxidants
Vitamins like A, C, and E act as antioxidants, protecting cells from free radicals—unstable molecules that can damage DNA, proteins, and lipids, leading to → Ageing, Cancer, Cardiovascular diseases, Neurodegenerative disorders.