What Are Micronutrients — and Why Can't Your Body Make Them?

Unlike the fat your body stores or the glucose it synthesizes, micronutrients — vitamins and minerals — must come almost entirely from food. Your cells use them to drive thousands of chemical reactions: converting food into energy, building bone, carrying oxygen through the blood, and repairing DNA. Without an adequate supply, those processes slow down or break down.

The word "micro" refers to quantity, not importance. You need only milligrams or even micrograms of most vitamins and minerals daily, but those tiny amounts have outsized effects. Think of micronutrients as the spark plugs of your metabolism — the engine (fueled by macronutrients) can't fire without them. For a grounding in how macronutrients and micronutrients work together, see our guide to what carbs, proteins, and fats actually do.

Total essential vitamins 13 (4 fat-soluble, 9 water-soluble) (National Institutes of Health, Office of Dietary Supplements)
Essential dietary minerals At least 16 recognized (Institute of Medicine, Dietary Reference Intakes)
Most common global deficiency Iron deficiency (World Health Organization)
Fat-soluble vitamins A, D, E, K
Vitamin stored least in body Vitamin C (water-soluble, excreted quickly)
Mineral most abundant in the body Calcium (~99% stored in bones and teeth) (National Institutes of Health, Office of Dietary Supplements)

Vitamins: Fat-Soluble vs. Water-Soluble

Vitamins split into two families based on how your body handles them, and that distinction matters for both sourcing and safety.

Fat-Soluble Vitamins (A, D, E, K)

These vitamins dissolve in fat, are absorbed alongside dietary fat, and can be stored in body fat and the liver. Because storage is possible, both deficiency and excess (usually from high-dose supplementation, not food) carry real risks. Vitamin A supports vision and immune function; vitamin D regulates calcium absorption and bone health; vitamin E acts as an antioxidant protecting cell membranes; vitamin K is essential for blood clotting and bone mineralization.

Water-Soluble Vitamins (B-complex and C)

These dissolve in water, are not stored in significant amounts, and excess is typically excreted in urine — which means you need a consistent daily supply. The eight B vitamins collectively support energy metabolism, red blood cell production, and nervous system health. Vitamin C is critical for collagen synthesis, immune defense, and enhancing the absorption of plant-based iron.

If you encounter unfamiliar terms like bioavailability or antioxidant while reading nutrition labels, our practical reference guide to nutritional terms offers plain-language definitions.

Micronutrient

A vitamin or mineral required by the body in small amounts for proper physiological function. Unlike macronutrients, micronutrients provide no calories but are essential for virtually every metabolic process.

Fat-soluble vitamin

A vitamin (A, D, E, or K) that requires dietary fat for absorption and can be stored in body fat and the liver. Because they accumulate, excessive intake from supplements can be harmful.

Water-soluble vitamin

A vitamin (the B-complex vitamins and vitamin C) that dissolves in water and is not stored in meaningful quantities. Excess amounts are generally excreted in urine, so a daily supply through food is important.

Trace mineral

A mineral the body needs in very small amounts — typically less than 100 milligrams per day — such as iron, zinc, iodine, or selenium. Despite the low quantity required, deficiencies have significant health consequences.

Bioavailability

The proportion of a nutrient that is actually absorbed and used by the body after consumption. Bioavailability varies depending on the food source, how the food is prepared, and individual factors like gut health.

Heme iron

A form of iron found in animal foods (meat, poultry, seafood) that is absorbed more efficiently by the human body than the non-heme iron found in plant foods.

Essential Minerals: Macro and Trace

Minerals are inorganic elements absorbed from soil and water through the foods we eat. Like vitamins, they fall into two tiers based on how much the body requires.

Macrominerals (needed in larger amounts)

  • Calcium: Builds and maintains bones and teeth; also supports muscle contraction and nerve signaling. Found in dairy, fortified plant milks, leafy greens, and canned fish with soft bones.
  • Magnesium: Participates in over 300 enzyme reactions, including protein synthesis and blood glucose control. Good sources include nuts, seeds, whole grains, and legumes.
  • Potassium: Regulates fluid balance and blood pressure. Bananas, potatoes, beans, and tomatoes are reliable sources.
  • Phosphorus: Works with calcium to build bone; also integral to DNA structure. Found in most protein-rich foods.

Trace Minerals (needed in smaller amounts)

  • Iron: Central to hemoglobin, which carries oxygen in red blood cells. Heme iron (meat, poultry, seafood) is absorbed more readily than non-heme iron (legumes, fortified cereals, spinach).
  • Zinc: Supports immune function, wound healing, and taste perception. Found in shellfish, meat, seeds, and legumes.
  • Iodine: Required for thyroid hormone production, which regulates metabolism. Iodized salt and seafood are common sources.
  • Selenium: Protects cells from oxidative damage; supports thyroid function. Brazil nuts and seafood are particularly rich sources.

Why Deficiencies Matter — and How to Spot the Risk

Micronutrient deficiencies are more common than many people realize, especially when diets rely heavily on processed foods that have been stripped of nutrients during manufacturing. Iron deficiency is the world's most widespread nutritional deficiency, and vitamin D insufficiency is notably prevalent across North America due to limited sun exposure and few naturally rich food sources.

Deficiencies rarely announce themselves dramatically at first. Early signs can be subtle: fatigue and brain fog may point to low iron or B12; bleeding gums can signal vitamin C shortfall; muscle cramps may reflect inadequate magnesium. These symptoms overlap with many conditions, so a healthcare provider is the right person to evaluate what's actually going on through blood testing.

Certain populations carry higher risk. People who are pregnant, follow restrictive diets, have gastrointestinal conditions affecting absorption, or are older adults may have increased needs or impaired uptake for specific nutrients. Nutritional needs also shift meaningfully across life stages — see our overview of how dietary needs shift from childhood to older adulthood for more on that.

This article is for general informational purposes and does not constitute medical advice. If you suspect a nutrient deficiency or have questions about your specific dietary needs, consult a qualified healthcare professional or registered dietitian.