Why Micronutrients Matter
Vitamins and minerals are collectively called micronutrients — nutrients required in relatively small amounts that the body cannot manufacture in sufficient quantities on its own. Unlike macronutrients such as carbohydrates, protein, and fat, micronutrients provide no calories. What they do provide is indispensable: they drive enzymatic reactions, support immune defense, build bone, regulate gene expression, and enable hundreds of other biological processes.
Most adults can meet their micronutrient needs through a varied, whole-food diet, yet national surveys consistently show shortfalls — particularly in vitamin D, calcium, potassium, and iron. Understanding what each key nutrient does and where to find it is a practical first step toward filling those gaps through food. For a broader nutritional picture, see our complete eating-well resource.
| Total vitamins essential to humans | 13 (National Institutes of Health, Office of Dietary Supplements) |
| Essential dietary minerals | At least 16 recognized (National Academy of Medicine) |
| Most common micronutrient deficiency globally | Iron deficiency anemia (World Health Organization) |
| Vitamin D deficiency prevalence (US adults) | Estimated ~35% (NHANES data, published in Nutrition Research) |
| Potassium adequate intake (adult) | 2,600–3,400 mg/day (National Academy of Medicine, 2019 DRI update) |
| Fat-soluble vitamins | A, D, E, K |
Key Vitamins: Functions and Food Sources
Vitamins are organic compounds grouped into two categories based on how the body stores them:
- Fat-soluble vitamins (A, D, E, K) — stored in fatty tissue and the liver. Because they accumulate, both chronic deficiency and excessive supplementation can cause problems.
- Water-soluble vitamins (C and the eight B vitamins) — not stored in significant amounts, so daily dietary intake matters more. Excess is typically excreted in urine.
Vitamin A
Supports vision (especially low-light), immune function, and cell growth. Found in liver, dairy, and eggs (as preformed retinol), and in orange-yellow produce like sweet potatoes and carrots (as provitamin A carotenoids).
Vitamin D
Critical for calcium absorption and bone density; also plays roles in immune regulation. Synthesized in skin through sun exposure; dietary sources include fatty fish, fortified dairy and plant milks, and egg yolks. Deficiency is widespread, especially in northern climates.
B Vitamins
The eight B vitamins (B1/thiamin, B2/riboflavin, B3/niacin, B5/pantothenic acid, B6, B7/biotin, B9/folate, and B12) collectively support energy metabolism, red blood cell production, and neurological function. Whole grains, legumes, leafy greens, eggs, and animal proteins are rich collective sources. B12 is found almost exclusively in animal products, making it a nutrient to monitor on fully plant-based diets.
Vitamin C
An antioxidant that supports collagen synthesis, wound healing, and immune function. Also enhances iron absorption from plant sources. Citrus fruits, bell peppers, kiwi, and strawberries are among the most concentrated sources.
Vitamin K
Exists in two main forms: K1 (phylloquinone), found in leafy greens, and K2 (menaquinones), found in fermented foods and some animal products. Both forms support blood clotting; K2 is also associated with bone and cardiovascular health.
~35%
US adults with low vitamin D status
Based on NHANES serum 25-hydroxyvitamin D data, as reported in peer-reviewed nutrition research.
300+
Enzymatic reactions requiring magnesium
Cited in National Institutes of Health Office of Dietary Supplements magnesium fact sheet.
10x
Greater heme vs. non-heme iron absorption
Absorption rate difference widely reported in nutritional biochemistry literature; varies by individual iron status.
Essential Minerals: What They Do and Where to Find Them
Minerals are inorganic elements — they come from soil and water and enter the food chain through plants and animals. Macrominerals (needed in larger amounts) include calcium, phosphorus, magnesium, potassium, sodium, and chloride. Trace minerals (needed in smaller amounts) include iron, zinc, copper, selenium, manganese, iodine, and fluoride.
Calcium
The most abundant mineral in the body, forming the structural basis of bones and teeth while also enabling muscle contraction and nerve transmission. Sources include dairy, fortified plant milks, canned fish with bones, and leafy greens such as bok choy and kale.
Iron
Essential for hemoglobin — the protein in red blood cells that carries oxygen. Heme iron (from meat, poultry, and fish) is more readily absorbed than non-heme iron (from legumes, tofu, and fortified cereals). Pairing non-heme sources with vitamin C significantly improves absorption.
Magnesium
Involved in more than 300 enzymatic reactions, including energy production, protein synthesis, and blood glucose regulation. Found in nuts, seeds, legumes, whole grains, and dark leafy greens.
Potassium
Supports fluid balance, nerve signaling, and muscle function — and helps counteract sodium's effect on blood pressure. Bananas, potatoes, beans, tomatoes, and dairy are good sources. Most Americans fall well below the adequate intake level.
Zinc and Selenium
Zinc supports immune function, wound healing, and protein synthesis; found in shellfish, red meat, legumes, and pumpkin seeds. Selenium acts as an antioxidant cofactor and supports thyroid function; Brazil nuts, seafood, and grains grown in selenium-rich soil are key sources.
Iodine
Required for thyroid hormone production, which regulates metabolism and development. Iodized salt, seafood, and dairy are primary sources in the US diet.
Micronutrient
A nutrient the body requires in small amounts to function properly. Vitamins and minerals are the two main categories of micronutrients.
Fat-soluble vitamin
A vitamin (A, D, E, or K) that dissolves in fat and is stored in the body's fatty tissue and liver. Because it accumulates, both deficiency and excessive intake can be problematic.
Water-soluble vitamin
A vitamin (C or any of the eight B vitamins) that dissolves in water and is not significantly stored, meaning regular dietary intake is important. Excess amounts are generally excreted in urine.
Heme iron
A form of iron found in animal-based foods — meat, poultry, and fish — that the body absorbs more efficiently than the non-heme form found in plant foods.
Trace mineral
A mineral the body needs in very small amounts, such as iron, zinc, selenium, and iodine. Despite the tiny quantities required, deficiencies can have significant health consequences.
Adequate Intake (AI)
A dietary reference value used when there is insufficient evidence to establish a firm Recommended Dietary Allowance. It represents an estimate believed to meet the needs of most healthy individuals.
Putting Micronutrients into Practice
No single food delivers every micronutrient, which is why dietary variety is the foundational strategy. A practical framework: fill half your plate with vegetables and fruit, include a protein source (animal or plant) at most meals, choose whole grains over refined, and incorporate nuts, seeds, or legumes regularly.
Learning to read a nutrition label can also help you identify fortified foods that meaningfully contribute to daily targets. While supplements can play a role in specific circumstances — for example, vitamin D in people with limited sun exposure, or B12 for those on plant-based diets — they are not a substitute for a nutritious diet. For a clear-eyed look at what supplements realistically offer, see our guide on dietary supplements.
Certain life stages carry distinct micronutrient considerations: iron and folate needs increase during pregnancy; older adults typically need more calcium and vitamin D; and growing children have different requirements than adults. If you belong to any of these groups, or manage a chronic health condition, consult a registered dietitian or your healthcare provider for personalized guidance. Micronutrient needs are also covered alongside broader dietary patterns in our article on dietary fibre, another commonly underconsumed nutrient.
This article is for general informational purposes only and does not constitute medical or nutritional advice. Consult a qualified healthcare professional before making significant changes to your diet or starting any supplement regimen.
Nutrient Interactions Can Work Both Ways
Some micronutrients enhance each other's absorption — for example, vitamin C increases non-heme iron uptake, and vitamin D is necessary for calcium absorption. Others compete: high doses of one mineral can interfere with the absorption of another (such as excess zinc reducing copper absorption). This is one reason a food-first approach, which delivers nutrients in naturally balanced proportions, is generally preferable to high-dose single-nutrient supplementation without clinical guidance.
The content on this site is for informational purposes only and is not a substitute for professional advice. Always consult a qualified professional for guidance specific to your situation.