Vitamin Classification and Function
Vitamins are organic compounds that the human body cannot synthesize in adequate quantities and therefore must obtain from dietary sources. They are categorized into two primary groups based on solubility: water-soluble and fat-soluble vitamins.
Water-Soluble Vitamins
Water-soluble vitamins include B vitamins (such as B1, B2, B3, B5, B6, B12) and vitamin C. These vitamins are absorbed in the small intestine and excess amounts are generally excreted in urine. They are not stored in significant quantities in the body.
Many B vitamins serve as coenzymes in energy metabolism. Vitamin B1 (thiamine) participates in carbohydrate metabolism. Vitamin B2 (riboflavin) functions in energy production. Vitamin B3 (niacin) supports DNA repair and energy metabolism.
Vitamin C (ascorbic acid) supports collagen synthesis, acts as an antioxidant, and supports immune function. It enhances the absorption of certain minerals, particularly iron from plant-based sources.
Fat-Soluble Vitamins
Fat-soluble vitamins include vitamins A, D, E, and K. These vitamins are absorbed in the presence of dietary fat and can be stored in adipose tissue and the liver. Excessive accumulation can occur with overconsumption.
Vitamin A supports vision, immune function, and cell differentiation. Vitamin D regulates calcium homeostasis and has immunomodulatory functions. Vitamin E functions as an antioxidant, protecting cell membranes. Vitamin K participates in blood coagulation and bone metabolism.
Food Sources
Different food sources provide different vitamin profiles. Leafy greens provide vitamins K and folate. Citrus fruits provide vitamin C. Fish provides vitamin D. Nuts and seeds provide vitamin E. Legumes provide B vitamins. A diverse diet generally provides an adequate spectrum of vitamins.
