vitamins

  1. Classification: Vitamins are micronutrients classified into two groups based on solubility: fat-soluble and water-soluble.

  2. Fat-Soluble Vitamins: Include A, D, E, and K.

  3. They are hydrophobic and absorbed with lipids, requiring micelles and chylomicrons.

  4. They are stored in the body with lipids, primarily in the liver and adipose tissues.

  5. Storage allows for skipping daily supplementation.

  6. Vitamin A: Found as active retinol (biological form) and provitamin A (beta-carotene) in plants. Beta-carotene is converted to retinol in the body. Beta-carotene is sensitive to sunlight, high temperature, and handling. Essential for growth and development of tissues, especially during pregnancy and neonatal growth.

  7. Vitamin D: Two forms: D3 (produced in animals) and D2 (produced in plants). Vitamin D3 is synthesized in the skin from 7-dehydrocholesterol upon exposure to UVB light. Vitamin D3 is then converted to its biologically active form in the liver and kidneys. Vitamin D enhances calcium absorption from the small intestine and reabsorption from the kidneys, regulating blood calcium levels.

  8. Vitamin E: Primarily found in plants. Powerful antioxidant that protects cells from oxidative damage caused by free radicals by donating electrons.

  9. Vitamin K: Main function is to promote blood clotting, specifically by enhancing the conversion of prothrombin to thrombin.

  10. Water-Soluble Vitamins: Include the B complex and C.

  11. They are hydrophilic and absorbed by dissolving in water in the blood.

  12. They are excreted in urine on a daily basis, meaning they are not stored in significant amounts.

  13. Daily consumption is generally required.

  14. Vitamin C (Ascorbic Acid): Found in citrus fruits, strawberries, kale, and broccoli. Humans, primates, and guinea pigs cannot synthesize vitamin C and must obtain it from the diet, making it an essential nutrient for these species. Other animals can synthesize it from glucose. Vitamin C is a powerful antioxidant, important for collagen synthesis (structural protein in connective tissues, healthy gums, skin, and tendons), essential for carnitine synthesis (aids fat burning), and enhances non-heme iron absorption. Deficiency can lead to scurvy.

  15. Vitamin B Complex: Includes B1 (thiamine) and B3 (niacin), among others. Act as cofactors for enzymes, particularly those involved in energy metabolism (ATP production).