| Total essential vitamins | 13 (4 fat-soluble, 9 water-soluble) (U.S. National Institutes of Health, Office of Dietary Supplements) |
| Essential minerals recognized | 16, including 7 macrominerals and 9 trace minerals (Dietary Reference Intakes, National Academies of Sciences) |
| Vitamin D inadequacy in U.S. adults | ~35% have insufficient blood levels (National Health and Nutrition Examination Survey (NHANES) data) |
| Iron deficiency prevalence | Most common nutritional deficiency worldwide (World Health Organization) |
| Folate requirement during pregnancy | 600 mcg DFE/day (vs. 400 mcg for non-pregnant adults) (NIH Office of Dietary Supplements) |
What Micronutrients Are and Why They Matter
Micronutrients are vitamins and minerals your body needs in relatively small amounts but cannot function well without. Unlike macronutrients like carbs, protein, and fat, micronutrients supply no calories — they act instead as catalysts and regulators for nearly every biological process, from energy metabolism to immune defense to bone maintenance.
There are two broad categories: vitamins (organic compounds) and minerals (inorganic elements). Vitamins are further split into fat-soluble (A, D, E, K) and water-soluble (C and the B vitamins). Fat-soluble vitamins are stored in body fat and liver tissue, meaning excess accumulates over time. Water-soluble vitamins are not stored in meaningful amounts and must be replenished regularly through food.
If you're just beginning to think about what you eat, the no-jargon nutrition starting point provides helpful foundational context before diving into specific nutrients.
| Total essential vitamins | 13 (4 fat-soluble, 9 water-soluble) (U.S. National Institutes of Health, Office of Dietary Supplements) |
| Essential minerals recognized | 16, including 7 macrominerals and 9 trace minerals (Dietary Reference Intakes, National Academies of Sciences) |
| Vitamin D inadequacy in U.S. adults | ~35% have insufficient blood levels (National Health and Nutrition Examination Survey (NHANES) data) |
| Iron deficiency prevalence | Most common nutritional deficiency worldwide (World Health Organization) |
| Folate requirement during pregnancy | 600 mcg DFE/day (vs. 400 mcg for non-pregnant adults) (NIH Office of Dietary Supplements) |
Key Vitamins: Functions, Sources, and Deficiency Signs
The table below summarizes the vitamins most commonly insufficient in American diets, along with their primary roles and food sources. This is general education, not a substitute for personalized guidance from a registered dietitian or healthcare provider.
Fat-soluble vitamins
Vitamins A, D, E, and K, which dissolve in fat and are stored in the body's liver and fatty tissue. Because they accumulate, excessive supplementation carries a risk of toxicity.
Water-soluble vitamins
Vitamin C and the eight B vitamins, which dissolve in water and are not stored in significant amounts. Excess is generally excreted in urine, making regular dietary intake important.
Trace minerals
Essential minerals required in very small quantities — typically less than 100 mg per day — including iron, zinc, iodine, selenium, and copper.
Daily Value (DV)
A reference amount established by the U.S. FDA used on Nutrition Facts labels to indicate how much a nutrient in a serving contributes to an average daily diet of 2,000 calories.
Deficiency
A state in which the body does not have enough of a specific nutrient to support normal physiological function. Deficiencies can develop gradually and may not produce obvious symptoms early on.
Bioavailability
The proportion of a nutrient consumed that is actually absorbed and used by the body. It varies based on food form, preparation method, and the presence of other nutrients or compounds in the same meal.
| Vitamin | Main Role | Common Food Sources | Deficiency Signs |
|---|---|---|---|
| Vitamin A | Vision, immune function, cell growth | Liver, dairy, eggs; beta-carotene in orange and dark leafy vegetables | Night blindness, dry skin, increased infection risk |
| Vitamin C | Collagen synthesis, antioxidant, iron absorption aid | Citrus fruits, bell peppers, broccoli, strawberries | Fatigue, bleeding gums, slow wound healing |
| Vitamin D | Calcium absorption, bone health, immune modulation | Fatty fish, fortified milk; skin synthesis via sunlight | Bone pain, muscle weakness, increased fracture risk |
| Vitamin B12 | Nerve function, red blood cell formation, DNA synthesis | Meat, fish, dairy, eggs; fortified foods for plant-based diets | Fatigue, tingling extremities, cognitive changes |
| Folate (B9) | DNA replication, cell division, fetal neural development | Leafy greens, legumes, fortified grains | Megaloblastic anemia; neural tube defects in pregnancy |
| Vitamin K | Blood clotting, bone protein activation | Kale, spinach, broccoli, fermented foods | Impaired clotting, easy bruising |
Keep in mind that how much of a vitamin your body actually absorbs depends on the food form, meal composition, and your individual health status. The science of bioavailability explains why a label's numbers don't always equal what reaches your cells.
Essential Minerals and Trace Elements
Minerals are divided into macrominerals (needed in larger amounts: calcium, magnesium, potassium, sodium, phosphorus) and trace minerals (needed in smaller amounts: iron, zinc, iodine, selenium, copper, manganese). Both groups are essential — the distinction is purely about quantity required, not importance.
- Calcium: Builds and maintains bones and teeth; also critical for muscle contraction and nerve signaling. Sources include dairy, fortified plant milks, tofu, and canned fish with bones.
- Iron: Carries oxygen in red blood cells. Heme iron (from meat) is absorbed more efficiently than non-heme iron (from legumes, spinach). Pairing plant iron sources with vitamin C improves absorption.
- Magnesium: Participates in over 300 enzymatic reactions, including energy production and protein synthesis. Nuts, seeds, whole grains, and leafy greens are good sources.
- Zinc: Supports immune defense, wound healing, and taste and smell perception. Found in shellfish, red meat, legumes, and pumpkin seeds.
- Iodine: Required for thyroid hormone synthesis, which regulates metabolism. Iodized salt and seafood are the primary U.S. sources.
- Selenium: Acts as an antioxidant cofactor and supports thyroid function. Brazil nuts, tuna, and eggs are concentrated sources.
- Potassium: Regulates fluid balance, nerve impulses, and heart rhythm. Beans, potatoes, bananas, and dairy are reliable sources.
When reviewing food labels, the % Daily Value column provides context for how a serving contributes to general intake targets. The Nutrition Facts label walkthrough breaks down how to read those figures meaningfully.
Supplements Are Not a Substitute for Food
Whole foods deliver micronutrients alongside fiber, phytonutrients, and other compounds that work synergistically in the body. Isolated supplements may fill specific gaps — particularly for vitamin D, B12, or folate in certain populations — but they cannot replicate the full nutritional matrix of a varied diet. Before starting any supplement regimen, consult a registered dietitian or your healthcare provider, especially if you have an existing health condition or take medications.