Micronutrients: A Plain-Language Reference for Vitamins and Minerals

What micronutrients are and why they matter

Vitamins and minerals are called micronutrients because the body needs them in small amounts compared to protein, fat, or carbohydrates. Small amounts do not mean trivial roles. These compounds regulate metabolism, build bone, support immune function, carry oxygen in the blood, and enable nerve signals, among dozens of other processes.

The 13 essential vitamins divide into two groups based on how the body handles them. Fat-soluble vitamins (A, D, E, and K) are stored in fatty tissue and the liver, so they accumulate over time. Water-soluble vitamins (vitamin C and the eight B vitamins) are not stored in significant quantities and need regular replenishment through food. Minerals split into major minerals, needed in amounts above 100 mg per day, and trace minerals, needed in smaller amounts but no less necessary.

Deficiency and excess are both possible. Most healthy adults eating a varied diet fall in a safe range, but certain life stages, health conditions, and eating patterns raise risk on either end. Nutritional needs shift meaningfully with age, which affects which micronutrients deserve closer attention at different points in life.

Key vitamins: what each one does and where to find it

Fat-soluble vitamins

Vitamin A supports vision (particularly in low light), immune defense, and cell growth. It comes in two forms: preformed vitamin A from animal foods like liver, eggs, and dairy, and provitamin A carotenoids from orange, yellow, and dark-green produce such as sweet potatoes, carrots, and spinach.

Vitamin D helps the body absorb calcium and supports bone health and immune regulation. Few foods contain meaningful amounts naturally; fatty fish, egg yolks, and fortified dairy are the main dietary sources. The body also synthesizes vitamin D from sunlight, though many factors limit how much is produced. Vitamin D is one of the most common shortfalls in the US population.

Vitamin E acts as an antioxidant and supports immune function. Nuts, seeds, and vegetable oils are the most concentrated sources, along with leafy greens.

Vitamin K is required for blood clotting and bone metabolism. Leafy green vegetables (kale, spinach, broccoli) supply the most. People taking certain blood-thinning medications should discuss their vitamin K intake with a healthcare provider.

Water-soluble vitamins

Vitamin C supports collagen production, wound healing, and antioxidant defense. Citrus fruits, bell peppers, strawberries, and broccoli are rich sources. Because vitamin C is water-soluble, excess is excreted, but very high supplement doses can cause gastrointestinal symptoms.

B vitamins are a group of eight nutrients that collectively support energy metabolism, red blood cell production, and nervous system function. Notable ones include B12 (found almost exclusively in animal products, making it a concern for people eating little or no meat), folate (critical during early pregnancy for neural tube development, found in legumes and leafy greens), and B6 (involved in protein metabolism, found in poultry, fish, potatoes, and bananas).

Key minerals: functions and food sources

Major minerals

Calcium builds and maintains bones and teeth, and also supports muscle contraction and nerve signaling. Dairy products are high in calcium, as are fortified plant milks, tofu made with calcium sulfate, and dark leafy greens like bok choy and kale.

Magnesium participates in over 300 enzymatic reactions, including those involved in energy production and muscle function. Whole grains, legumes, nuts, seeds, and dark chocolate are reliable sources. Surveys consistently show that more than half of Americans fall short of recommended intake through diet alone.

Potassium helps regulate fluid balance and blood pressure. Beans, lentils, potatoes, bananas, and dairy all supply meaningful amounts.

Trace minerals

Iron is a component of hemoglobin and carries oxygen in red blood cells. Red meat, poultry, and seafood provide heme iron, which the body absorbs more readily. Plant sources such as lentils, tofu, and fortified cereals supply non-heme iron; pairing them with vitamin C-rich foods improves absorption.

Zinc supports immune function, wound healing, and DNA synthesis. Oysters are an unusually concentrated source; beef, poultry, beans, and pumpkin seeds also contribute.

Selenium functions as an antioxidant and supports thyroid hormone production. Brazil nuts contain very high amounts (a single nut can meet the daily requirement); seafood and whole grains are more moderate sources.

Building a diet with consistent variety across food groups covers most micronutrient needs without requiring detailed tracking. A structured weekly grocery approach makes that variety easier to maintain over time.

Supplements: when they help and when to be careful

Supplements can correct genuine deficiencies, but they do not replicate all the benefits of whole foods, which supply fiber, phytonutrients, and combinations of nutrients that interact in ways isolated supplements do not. Before adding a supplement, it is worth identifying whether an actual gap exists rather than assuming one does.

Groups with documented higher risk of specific shortfalls include people who eat no animal products (B12, vitamin D, omega-3s), older adults (vitamin D, calcium, B12), pregnant or planning-to-conceive individuals (folate, iron), and people with certain absorption conditions. A healthcare provider can order blood tests to confirm a deficiency before a supplement is recommended.

Fat-soluble vitamins (A, D, E, K) warrant extra caution in supplement form because they accumulate and can reach toxic levels. Water-soluble vitamins are less prone to toxicity but not entirely without risk at very high doses. Any supplementation decision in the context of a diagnosed condition, pregnancy, or current medication should involve a qualified healthcare professional.

This article is for general informational and educational purposes only and is not a substitute for professional medical or dietary advice. Consult a qualified healthcare provider or registered dietitian before making changes based on your personal health needs.