Vitamins and Minerals at a Glance: Key Functions and Common Food Sources

Why Micronutrients Matter

Vitamins and minerals — collectively called micronutrients — are compounds the body requires in relatively small amounts to sustain thousands of physiological processes. Unlike macronutrients (carbohydrates, proteins, and fats), they provide no calories, yet they are indispensable for converting food into energy, building and repairing tissue, regulating immune responses, and maintaining fluid balance. For a broader view of how micronutrients fit alongside the macros, see our plain-language macronutrient guide.

Deficiencies in key micronutrients are not rare even in high-income countries. Suboptimal intakes of vitamins D, B12, and iron, for example, are documented across various demographic groups in the United States. This reference is designed to help you recognize what each nutrient does and where to find it in everyday food — not to replace individualized guidance from a healthcare provider.

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

Fat-soluble vitamins are absorbed alongside dietary fat and stored in the liver and fatty tissues, meaning they accumulate over time. This storage capacity is an advantage during periods of low intake but also means excess supplementation carries risk.

• Vitamin A — Supports vision (particularly low-light adaptation), immune defense, and cellular differentiation. Found in liver, eggs, dairy, and as provitamin A carotenoids in orange and dark-green vegetables such as sweet potatoes, carrots, and spinach.
• Vitamin D — Regulates calcium absorption and plays roles in immune modulation and muscle function. Synthesized in skin exposed to UVB light; dietary sources include fatty fish (salmon, mackerel), fortified dairy and plant milks, and egg yolks.
• Vitamin E — Acts as a lipid-soluble antioxidant, protecting cell membranes from oxidative damage. Nuts, seeds, wheat germ oil, and sunflower oil are concentrated sources.
• Vitamin K — Essential for blood coagulation (K1, or phylloquinone) and bone protein activation (K2, or menaquinone). Leafy greens — kale, collards, broccoli — are rich in K1; fermented foods and some animal products supply K2.

Water-Soluble Vitamins: The B Complex and Vitamin C

Water-soluble vitamins are not stored in meaningful quantities (B12 is a notable partial exception) and must be replenished regularly through diet. Excess amounts are generally excreted in urine.

• B1 (Thiamine) — Cofactor for energy metabolism, particularly carbohydrate breakdown; supports nerve function. Whole grains, legumes, and pork are good sources.
• B2 (Riboflavin) — Participates in cellular energy production and fatty acid metabolism. Found in dairy, eggs, lean meats, and fortified cereals.
• B3 (Niacin) — Required for NAD/NADH reactions central to energy metabolism; also supports DNA repair. Poultry, fish, peanuts, and fortified grains supply significant amounts. Niacin's derivative niacinamide has also attracted attention in skincare — see what the evidence says about niacinamide.
• B6 (Pyridoxine) — Involved in amino acid metabolism and neurotransmitter synthesis. Chickpeas, bananas, poultry, and potatoes are reliable sources.
• B9 (Folate) — Critical for DNA synthesis and cell division; particularly important during pregnancy. Dark leafy greens, lentils, and fortified cereals provide substantial folate.
• B12 (Cobalamin) — Necessary for red blood cell formation and neurological function. Found almost exclusively in animal products; people following plant-based diets typically require a supplement or fortified foods.
• Vitamin C — Antioxidant; essential for collagen synthesis, iron absorption from plant foods, and immune function. Citrus fruits, bell peppers, strawberries, and broccoli are top sources.

Essential Minerals: From Calcium to Zinc

Minerals are inorganic elements drawn from soil and water that the body cannot synthesize. They serve structural roles (bone, teeth) and regulatory functions (nerve signaling, enzyme activity, fluid balance).

• Calcium — Builds and maintains bone density; supports muscle contraction and nerve transmission. Dairy products, fortified plant milks, sardines with bones, and tofu made with calcium sulfate are strong sources.
• Iron — Core component of hemoglobin (oxygen transport) and myoglobin (muscle oxygen storage). Heme iron from red meat and poultry is more readily absorbed; non-heme iron from legumes, spinach, and fortified cereals is enhanced by pairing with vitamin C.
• Magnesium — Cofactor in over 300 enzymatic reactions; supports protein synthesis, muscle and nerve function, and blood glucose control. Nuts, seeds, whole grains, and dark chocolate are good sources.
• Potassium — Regulates fluid balance, muscle contractions, and nerve signals; supports healthy blood pressure. Bananas, potatoes, beans, and leafy greens are well-known sources.
• Zinc — Involved in immune cell function, wound healing, protein synthesis, and taste perception. Oysters, red meat, poultry, beans, and pumpkin seeds are common sources.
• Selenium — Antioxidant component of selenoproteins; supports thyroid hormone metabolism. Brazil nuts, seafood, and whole grains provide selenium, though amounts vary with soil content.
• Iodine — Required for thyroid hormone production, which governs metabolism and growth. Iodized salt, seafood, dairy, and seaweed are primary sources.

For practical guidance on interpreting nutrient information on food packaging, our nutrition label guide explains what % Daily Value figures actually mean in everyday terms. And if you are newer to thinking about diet holistically, our nutrition fundamentals primer offers a broader starting point.

This article is for general informational and educational purposes only and does not constitute medical or dietary advice. Individual nutritional needs vary significantly based on age, health status, medications, and other factors. Consult a registered dietitian or qualified healthcare provider before making changes to your diet or starting any supplement regimen.