Vitamins and Minerals: What Each One Does and Where to Get Them

Why Vitamins and Minerals Matter

Vitamins and minerals are micronutrients — substances required in small amounts that the body cannot synthesize in sufficient quantities on its own, and must therefore obtain from food. Unlike macronutrients (carbohydrates, proteins, and fats) which provide energy, micronutrients serve as cofactors for enzymatic reactions, structural components of tissues, and regulators of physiological processes ranging from bone formation to blood clotting to immune function.

The distinction between vitamins and minerals is chemical. Vitamins are organic compounds — carbon-containing molecules made by plants and animals — and include the fat-soluble vitamins A, D, E, and K, and the water-soluble vitamins C and the eight B vitamins. Minerals are inorganic elements derived from soil and water that plants absorb and animals consume. Essential minerals include macrominerals needed in larger amounts (calcium, phosphorus, magnesium, sodium, potassium, chloride, sulfur) and trace minerals needed in smaller quantities (iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium, molybdenum).

Deficiencies in specific micronutrients cause well-characterized diseases: vitamin C deficiency causes scurvy, vitamin D deficiency causes rickets in children, iodine deficiency causes goiter and impaired neurological development, and iron deficiency causes anemia. Even subclinical deficiencies — below the threshold for clinical disease — can impair immune function, cognitive performance, and physical capacity in ways that are often overlooked.

Fat-Soluble Vitamins: A, D, E, and K

Vitamin A is essential for vision (particularly night vision), immune function, and cellular differentiation. It exists in two forms: preformed vitamin A (retinol and its esters) found in animal products like liver, eggs, and dairy, and provitamin A carotenoids (primarily beta-carotene) found in orange and yellow vegetables and leafy greens. Deficiency, most common in developing countries, causes night blindness and increased susceptibility to infection. Excess vitamin A from supplements (not food sources) can be toxic, causing liver damage and, in pregnant women, birth defects.

Vitamin D functions as a hormone as much as a vitamin. Its primary role is regulating calcium and phosphorus absorption for bone health, but vitamin D receptors are found in virtually every tissue in the body and it plays roles in immune regulation, muscle function, and cardiovascular health. The primary source is synthesis in skin upon ultraviolet B sunlight exposure; dietary sources (fatty fish, egg yolks, fortified foods) contribute modestly. Deficiency is extremely common globally — estimated to affect over a billion people — particularly in northern latitudes, darker-skinned individuals, the elderly, and those who spend little time outdoors. Supplementation of 1,000 to 2,000 IU daily is widely recommended for those at risk.

Vitamin E is a family of eight compounds, with alpha-tocopherol being the most biologically active. It acts as a fat-soluble antioxidant, protecting cell membranes from oxidative damage. Deficiency is rare in healthy adults but causes nerve and muscle damage in those with fat malabsorption disorders. Best sources include sunflower seeds, almonds, wheat germ oil, and spinach. Vitamin K exists in two main forms: K1 (phylloquinone) from leafy green vegetables, essential for blood clotting, and K2 (menaquinones) from fermented foods and some animal products, important for directing calcium to bones rather than arteries.

Water-Soluble Vitamins: The B Complex and Vitamin C

The eight B vitamins — B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin) — are chemically distinct but collectively involved in energy metabolism, functioning as coenzymes in pathways that extract energy from carbohydrates, fats, and proteins. Several have additional specialized roles: folate is critical for DNA synthesis and is required before and during pregnancy to prevent neural tube defects; B12 is essential for neurological function and red blood cell formation and is found almost exclusively in animal products, making supplementation important for vegans and vegetarians.

Vitamin C (ascorbic acid) is required for collagen synthesis, making it essential for wound healing, skin integrity, and vascular health. It also acts as a powerful water-soluble antioxidant and enhances the absorption of non-heme (plant-sourced) iron. Deficiency causes scurvy — once a major cause of death among sailors on long voyages — characterized by bleeding gums, bruising, and poor wound healing. Best sources include citrus fruits, bell peppers, kiwi, strawberries, and broccoli. Unlike fat-soluble vitamins, excess water-soluble vitamins are generally excreted in urine, making toxicity from food sources rare though possible from high-dose supplements.

Essential Minerals: Calcium, Iron, Magnesium, and Zinc

Calcium is the most abundant mineral in the body, with 99 percent stored in bones and teeth where it provides structural rigidity. The remaining 1 percent in blood and soft tissues regulates muscle contraction, nerve transmission, and blood clotting. The body maintains blood calcium within a tight range, drawing from bone reserves when dietary intake is inadequate — a process that, over time, reduces bone density and increases fracture risk. Best sources are dairy products, fortified plant milks, tofu made with calcium sulfate, canned fish with bones, and leafy greens (though oxalates in some greens reduce absorption).

Iron is the central component of hemoglobin, the protein in red blood cells that carries oxygen from lungs to tissues, and of myoglobin in muscle. Iron-deficiency anemia is the world's most common nutritional deficiency, affecting an estimated 1.6 billion people. Iron exists in two dietary forms: heme iron from animal products (highly bioavailable) and non-heme iron from plants (less bioavailable but enhanced by vitamin C consumed simultaneously). Magnesium participates in over 300 enzymatic reactions and is required for ATP synthesis, protein production, and DNA repair. Many adults consume insufficient magnesium; deficiency is associated with muscle cramps, fatigue, and increased risk of type 2 diabetes and cardiovascular disease. Zinc is essential for immune function, wound healing, DNA synthesis, and the sense of taste and smell. Deficiency impairs immune response and growth, and is particularly problematic in children.

Iodine, Selenium, and Other Trace Minerals

Iodine is required exclusively for the synthesis of thyroid hormones, which regulate metabolism, growth, and neurological development. Severe deficiency during pregnancy causes cretinism — irreversible intellectual disability in the child — and iodine deficiency remains the leading preventable cause of intellectual disability worldwide. Iodized salt, introduced in the early 20th century, dramatically reduced deficiency in many countries. Selenium is a component of selenoproteins with antioxidant functions and plays roles in thyroid hormone metabolism and immune function. Brazil nuts are an exceptionally concentrated source — a single nut can provide an entire day's requirement. Copper supports iron metabolism, antioxidant enzyme function, and connective tissue formation. Deficiency is rare but can occur in those with high zinc supplementation, which competes with copper absorption.

Potassium is the primary intracellular cation and works in tandem with sodium to regulate fluid balance, nerve signaling, and muscle contraction. Most adults consume far too little potassium (found in fruits, vegetables, beans, and dairy) and far too much sodium, contributing to elevated blood pressure. Chromium has a role in insulin signaling, though the evidence for chromium supplementation improving blood sugar control in diabetes is inconsistent. Fluoride, while not strictly essential, is incorporated into tooth enamel and bone mineral and is highly effective at preventing dental caries when present in water or applied topically through toothpaste.

Getting Micronutrients from Food vs. Supplements

Food sources of vitamins and minerals generally outperform supplements for several reasons. Whole foods contain nutrients in complex matrices alongside fiber, phytochemicals, and other compounds that enhance absorption and provide synergistic benefits. Beta-carotene from carrots behaves differently in the body than isolated beta-carotene capsules; the latter in high doses was found to increase lung cancer risk in smokers in clinical trials. Similarly, vitamin E supplements did not replicate the benefits observed in populations with high food-based vitamin E intake.

Nonetheless, certain populations have genuine supplementation needs that are difficult to meet through diet alone. Vegans require vitamin B12 supplementation. Pregnant women need supplemental folate to prevent neural tube defects and often need additional iron. Older adults frequently need vitamin D supplementation due to reduced skin synthesis efficiency. Individuals with diagnosed deficiencies, malabsorption conditions, or restricted diets may need targeted supplementation under medical guidance. For the general population without specific deficiencies, a varied diet rich in colorful vegetables, fruits, whole grains, legumes, nuts, and lean proteins provides the full spectrum of micronutrients more effectively and safely than a collection of supplements.