Vitamins are essential organic compounds required in small amounts for various biochemical processes that sustain life. Unlike macronutrients such as carbohydrates, proteins, and fats, vitamins do not provide energy but play crucial roles in enzymatic reactions, cellular function, and overall metabolic health. Most vitamins cannot be synthesized in sufficient quantities by the human body and must be obtained through diet or supplements. They are classified into two major categories: fat-soluble (A, D, E, and K) and water-soluble (B-complex and C). Each vitamin has specific functions and is found in distinct food sources.

Fat-soluble vitamins are stored in the body’s fatty tissues and liver, allowing them to be utilized as needed. Vitamin A, also known as retinol, is vital for vision, immune function, and cell differentiation. It is found in liver, dairy products, and carotenoid-rich vegetables like carrots and sweet potatoes. Vitamin D, synthesized by the skin upon exposure to sunlight, regulates calcium and phosphorus homeostasis, essential for bone health. Dietary sources include fatty fish, egg yolks, and fortified dairy products. Vitamin E, comprising tocopherols and tocotrienols, functions as an antioxidant, protecting cell membranes from oxidative damage. Nuts, seeds, and vegetable oils are excellent sources. Vitamin K, necessary for blood clotting and bone metabolism, is found in leafy greens, broccoli, and fermented foods.

Water-soluble vitamins, which include the B-complex group and vitamin C, must be regularly consumed as they are not stored in the body. The B-complex vitamins play diverse biochemical roles, primarily as coenzymes in energy metabolism. Thiamine (B1) helps convert carbohydrates into energy and is found in whole grains, pork, and legumes. Riboflavin (B2) is essential for redox reactions and is present in dairy products, eggs, and leafy vegetables. Niacin (B3) participates in the production of NAD and NADP, crucial for cellular respiration, and can be obtained from meat, fish, and whole grains. Pantothenic acid (B5), a component of coenzyme A, is widespread in foods like avocados, chicken, and whole grains.

Pyridoxine (B6) is involved in amino acid metabolism and neurotransmitter synthesis, and is found in bananas, poultry, and potatoes. Biotin (B7), crucial for fatty acid synthesis and gluconeogenesis, is abundant in eggs, nuts, and organ meats. Folate (B9) supports DNA synthesis and is particularly important during pregnancy to prevent neural tube defects; sources include leafy greens, legumes, and citrus fruits. Cobalamin (B12), essential for red blood cell formation and neurological function, is found only in animal products such as meat, eggs, and dairy.

Vitamin C, or ascorbic acid, is a powerful antioxidant and is vital for collagen synthesis, wound healing, and immune support. It enhances iron absorption and is abundant in citrus fruits, bell peppers, and strawberries.

Understanding the biochemical functions and dietary sources of vitamins highlights their indispensable role in maintaining health. A balanced diet rich in diverse, nutrient-dense foods ensures adequate vitamin intake, reducing the risk of deficiencies and promoting overall well-being.

Sources:
https://medlineplus.gov/ency/article/002399.htm
https://www.nhs.uk/conditions/vitamins-and-minerals/
https://www.betterhealth.vic.gov.au/health/healthyliving/Vitamins-and-minerals