Micronutrients are the vitamins and minerals your body needs in small amounts to function properly. Unlike proteins, fats, and carbohydrates, which you consume in grams, micronutrients are measured in milligrams or micrograms. They don’t provide calories or energy directly, but they’re essential for digestion, hormone production, brain function, oxygen transport, and hundreds of other biological processes. There are roughly 30 micronutrients considered essential, and your body can’t make most of them on its own.
Vitamins: Water-Soluble vs. Fat-Soluble
Vitamins split into two groups based on how your body absorbs and stores them. The distinction matters because it affects how quickly you can become deficient and whether overconsumption poses a risk.
Water-soluble vitamins dissolve in water and aren’t stored in large amounts. Your body uses what it needs and excretes the rest through urine, which means you need a steady daily supply. This group includes vitamin C and the eight B vitamins: B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B9 (folate), and B12. Each plays a distinct role. Thiamine helps cells convert carbohydrates into energy and supports nerve function. Folate and B12 work together to form red blood cells and produce DNA. Biotin is involved in metabolizing proteins and carbohydrates. Vitamin C acts as an antioxidant and supports immune function and tissue repair.
Fat-soluble vitamins, which include A, D, E, and K, require dietary fat to be absorbed. In your small intestine, they get bundled into tiny fat clusters called micelles, then packaged into particles that travel through your lymphatic system before entering the bloodstream. Because they’re stored in fatty tissue and the liver, your body retains them much longer than water-soluble vitamins. This is useful during periods of low intake, but it also means excess amounts can accumulate to harmful levels over time.
Minerals: Macrominerals and Trace Minerals
Minerals are inorganic elements your body can’t produce. They’re divided into two categories based on how much you need.
Macrominerals are required in larger quantities. This group includes calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Calcium and phosphorus are the primary structural components of bones and teeth. Magnesium supports over 300 enzymatic reactions, including muscle and nerve function. Potassium and sodium regulate fluid balance and electrical signals in your heart and muscles. The recommended daily magnesium intake for adults ranges from 310 mg for younger women to 420 mg for men over 30.
Trace minerals are needed in much smaller amounts but are no less important. Iron, zinc, iodine, selenium, copper, manganese, fluoride, and cobalt all fall into this category. Iron is a component of hemoglobin and myoglobin, the proteins that carry oxygen in your blood and muscles. Zinc is part of more than 200 enzymes and plays roles in tissue repair, growth, and hormone production. Iodine is an integral component of thyroid hormones, which regulate metabolism. Selenium helps destroy harmful peroxides in your cells. Copper participates in energy metabolism and helps your body absorb and use iron.
The Most Common Deficiencies
Three micronutrient deficiencies stand out as global public health concerns. Iron deficiency is the most widespread. It leads to anemia, a condition where your blood can’t carry enough oxygen, causing fatigue, weakness, shortness of breath, and dizziness. The World Health Organization estimates that 42% of children under five and 40% of pregnant women worldwide are anemic.
Vitamin A deficiency is the leading cause of preventable blindness in children and increases vulnerability to severe infections like measles and diarrheal disease. It’s most common in low-income regions but can also occur during late pregnancy.
Iodine deficiency can cause brain damage in severe cases and, during pregnancy, raises the risk of stillbirth and developmental problems. Even mild deficiency reduces intellectual capacity. Globally, about 66% of households have access to iodized salt, the primary strategy for preventing this deficiency.
How Your Body Absorbs Micronutrients
Not all micronutrients in food are equally available to your body. Bioavailability, the proportion your body actually absorbs and uses, varies significantly depending on the form of the nutrient and what you eat it with.
Vitamin C is one of the best-known absorption enhancers. Eating vitamin C-rich foods alongside iron-containing foods increases iron uptake. Vitamins A and B2 (riboflavin) also improve iron absorption and mobilization. In fact, riboflavin deficiency may be a primary cause of anemia in some populations because it impairs iron use. Fat-soluble vitamins (A, D, E, K) absorb much better when consumed with dietary fat, so eating a salad with olive oil or avocado helps you get more from those leafy greens.
On the other side, several compounds reduce absorption. Phytic acid, found in legumes, cereal grains, and seeds, binds to calcium, zinc, and iron, dramatically reducing how much your intestines can take up. Polyphenols (in tea and coffee) and high-fiber diets can also inhibit mineral absorption. Plant-based iron is roughly 44% less bioavailable than iron from animal sources. In a vegetarian diet, only about 10% of dietary iron gets absorbed compared to 18% in a mixed diet.
Where to Find Micronutrients in Food
A varied diet is the most reliable way to cover your micronutrient needs. Some foods are particularly nutrient-dense. Organ meats, small dried fish, and bivalves like mussels and clams are among the richest sources of vitamin B12. Liver, dark green leafy vegetables, eggs, and pulses (beans, lentils, chickpeas) top the list for folate. Quinoa is another strong folate source that often gets overlooked.
For fat-soluble vitamins, fatty fish, eggs, and fortified dairy provide vitamin D. Orange and yellow vegetables supply beta-carotene, which your body converts to vitamin A. Nuts and seeds are good sources of vitamin E. Fermented foods and leafy greens deliver vitamin K. For minerals, dairy products and canned fish with bones are calcium-rich. Red meat, shellfish, and legumes provide iron and zinc. Brazil nuts are one of the most concentrated food sources of selenium.
The recommended vitamin D intake for most adults aged 19 to 70 is 600 IU per day, rising to 800 IU for adults over 70. Many people, especially those living in northern latitudes or spending limited time outdoors, struggle to meet this through food and sunlight alone.
Upper Limits and Supplement Safety
Because fat-soluble vitamins accumulate in your body, they carry a real risk of toxicity at high doses. The tolerable upper intake level for vitamin A in adults is 3,000 micrograms per day of preformed vitamin A (the type found in liver, supplements, and fortified foods). Going above this level consistently can cause nausea, headaches, liver damage, and, during pregnancy, birth defects. Beta-carotene from fruits and vegetables does not carry the same risk because your body regulates how much it converts.
Water-soluble vitamins are generally safer in high doses since your kidneys flush out the excess, though very high supplemental doses of B6 can cause nerve damage over time. With minerals, the margin between a helpful and harmful dose can be narrow. Iron supplements, for instance, are one of the most common causes of poisoning in young children.
For most people eating a reasonably varied diet, food alone provides adequate amounts of nearly all micronutrients. Supplementation is most beneficial when there’s a documented deficiency, a restricted diet, or a life stage with increased needs, such as pregnancy or older age.