Micronutrients Reference: Vitamins and Minerals Every Adult Should Know

What Are Micronutrients and Why Do They Matter?

Micronutrients — vitamins and minerals — are compounds your body needs in relatively small amounts but cannot function without. Unlike macronutrients, they don't supply calories directly; instead, they act as essential cofactors in thousands of biochemical processes, from energy metabolism to immune defense and bone formation.

Most US adults can meet their needs through a varied, whole-food diet. However, national nutrition surveys consistently show that certain nutrients — particularly vitamin D, calcium, potassium, and dietary fiber — fall short of recommended intakes across wide segments of the population. Understanding what each micronutrient does, and where to find it, is the foundation of smarter eating. For broader context on how vitamins and minerals work alongside macronutrients, see our guide to macronutrients.

This article is for general informational and educational purposes only and is not a substitute for personalized medical or nutritional advice. Consult a qualified healthcare professional before making significant changes to your diet or if you suspect a deficiency.

Key Vitamins: Roles, Sources, and Deficiency Signs

Vitamins are divided into two broad categories: fat-soluble (A, D, E, K), which are stored in body tissues, and water-soluble (C and the B vitamins), which are not stored and must be replenished more regularly.

Fat-Soluble Vitamins

• Vitamin A: Supports vision, immune function, and cell growth. Found in liver, dairy, eggs, and as beta-carotene in orange and leafy green vegetables. Deficiency can impair night vision and immune response.
• Vitamin D: Regulates calcium absorption and supports bone health, immune function, and mood. Synthesized through sun exposure; dietary sources include fatty fish, fortified dairy, and eggs. Deficiency is widespread and linked to weakened bones and immune dysfunction.
• Vitamin E: An antioxidant that protects cell membranes. Found in nuts, seeds, vegetable oils, and leafy greens. Deficiency is uncommon in healthy adults but may occur with fat-malabsorption conditions.
• Vitamin K: Critical for blood clotting and bone metabolism. Found in green leafy vegetables, fermented foods, and some animal products. People taking anticoagulant medications should discuss vitamin K intake with their provider.

Water-Soluble Vitamins

• Vitamin C: Supports collagen synthesis, wound healing, and immune function; also enhances iron absorption. Found in citrus fruits, bell peppers, broccoli, and strawberries. Deficiency causes scurvy, now rare in the US.
• B Vitamins (B1, B2, B3, B5, B6, B7, B9, B12): Collectively essential for energy metabolism, red blood cell production, and nervous system function. Found across a wide range of foods — whole grains, legumes, meat, dairy, eggs, and leafy greens. Vitamin B12, found almost exclusively in animal products, deserves particular attention for those following plant-based diets.

For practical guidance on spotting micronutrient information on packaging, see our article on reading a nutrition label.

Essential Minerals: Macrominerals and Trace Minerals

Minerals are inorganic elements that support bone structure, fluid balance, nerve transmission, and hundreds of enzymatic reactions. They're grouped by the quantity the body requires.

Macrominerals (needed in larger amounts)

• Calcium: The most abundant mineral in the body; essential for bone density, muscle contraction, and nerve function. Found in dairy, fortified plant milks, canned fish with bones, tofu, and leafy greens. Chronic low intake raises the risk of osteoporosis.
• Magnesium: Involved in over 300 enzymatic reactions, including energy production, protein synthesis, and blood pressure regulation. Found in nuts, seeds, legumes, whole grains, and dark leafy greens.
• Potassium: Regulates fluid balance, muscle contractions, and nerve signals; helps counteract sodium's effect on blood pressure. Found in bananas, potatoes, beans, and leafy greens. Many American adults do not meet the adequate intake level.
• Phosphorus: Works with calcium in bone and teeth formation and is involved in energy metabolism. Found in protein-rich foods including meat, poultry, fish, dairy, and legumes.
• Sodium and Chloride: Maintain fluid balance and support nerve and muscle function. Most Americans consume excess sodium, primarily through processed foods, which is associated with elevated blood pressure.

Trace Minerals (needed in smaller amounts)

• Iron: Carries oxygen in the blood via hemoglobin. Found in red meat, poultry, seafood (heme iron) and beans, lentils, and fortified cereals (non-heme iron). Deficiency — the most common nutritional deficiency globally — causes fatigue and anemia.
• Zinc: Supports immune function, wound healing, and protein synthesis. Found in meat, shellfish, legumes, and seeds.
• Iodine: Essential for thyroid hormone production, which regulates metabolism and growth. Found in iodized salt, seafood, and dairy. Deficiency can impair thyroid function.
• Selenium: Acts as an antioxidant and supports thyroid function. Found in Brazil nuts, seafood, and whole grains.

A varied whole-food diet generally covers most micronutrient needs. When gaps exist, food should be the first strategy; supplementation may be appropriate in specific contexts — always guided by a healthcare provider. For a deeper look at common misconceptions about nutrition, including supplements, visit our piece on nutrition myths and the science.