| Number of essential vitamins | 13 (NIH Office of Dietary Supplements) |
| Number of essential dietary minerals | Approximately 16 (General nutritional science consensus) |
| Most common nutrient deficiency worldwide | Iron deficiency (World Health Organization) |
| Vitamin produced by skin in sunlight | Vitamin D (NIH Office of Dietary Supplements) |
| Nutrient critical for early pregnancy | Folate (vitamin B9) (CDC folic acid guidance) |
| Vitamin found almost exclusively in animal foods | Vitamin B12 (NIH Office of Dietary Supplements) |
What Are Micronutrients?
Unlike carbohydrates, proteins, and fats, micronutrients — vitamins and minerals — provide no calories. Instead, they act as essential cofactors in nearly every biological process: converting food into energy, building bone, synthesizing hormones, and repairing DNA. The word "micro" refers to the quantities needed (milligrams or micrograms), not their importance.
The human body cannot synthesize most micronutrients on its own, which is why diet is the primary source. A handful of exceptions exist — the skin produces vitamin D in response to sunlight, and gut bacteria generate some vitamin K — but these contributions are often insufficient on their own. Consistent dietary gaps can lead to deficiency states that impair health in measurable ways.
Micronutrient
A vitamin or mineral required by the body in small amounts to support normal physiological function. Unlike macronutrients, micronutrients do not provide energy (calories).
Fat-soluble vitamin
A vitamin (A, D, E, or K) that dissolves in fat and is stored in the body's fatty tissues and liver. Because they accumulate, excessive intake can potentially become harmful.
Water-soluble vitamin
A vitamin (C and the B vitamins) that dissolves in water and is not stored in significant quantities. Excess amounts are generally excreted in urine, requiring more regular dietary intake.
Trace mineral
A mineral the body requires in very small amounts — typically less than 100 mg per day. Examples include iron, zinc, selenium, and iodine.
Bioavailability
The proportion of a nutrient that is actually absorbed and used by the body after ingestion. It varies by food source, preparation method, and individual factors.
Deficiency
A condition caused by inadequate intake or absorption of a nutrient over time, often resulting in specific, measurable health impairments. Iron deficiency anemia is a common example.
Key Vitamins: Roles and Food Sources
Vitamins are divided into two categories based on how the body stores them:
- Fat-soluble vitamins (A, D, E, K) accumulate in fatty tissue and the liver. Because they are stored, excessive intake — particularly from concentrated supplements — can reach toxic levels over time.
- Water-soluble vitamins (B complex, C) are not stored in significant amounts; excess is excreted in urine. This means they need more regular dietary replenishment, but toxicity risk from food sources is low.
Vitamin A supports vision in low light, immune defense, and cell differentiation. Preformed vitamin A (retinol) is found in liver, dairy, and eggs; provitamin A (beta-carotene) comes from orange and dark-green vegetables such as sweet potatoes and spinach.
Vitamin D regulates calcium absorption and is critical for bone density, immune function, and muscle performance. Food sources include fatty fish, egg yolks, and fortified foods, though sunlight exposure remains a major contributor for many people.
B vitamins — thiamine, riboflavin, niacin, B6, folate, B12, and others — collectively support energy metabolism and nervous system function. Folate is especially critical during early pregnancy for neural tube development. B12 is found almost exclusively in animal products, making it a nutrient of concern for those following plant-based diets.
Vitamin C supports collagen synthesis, immune function, and acts as an antioxidant. Citrus fruits, bell peppers, and broccoli are among the richest sources.
Supplements vs. Whole Foods
Supplements can help address diagnosed deficiencies, but they are not a straightforward substitute for a varied diet. Whole foods provide vitamins and minerals alongside fiber, phytonutrients, and other compounds that may affect how nutrients are absorbed and used. Before starting any supplement regimen, speak with a qualified healthcare provider to determine whether one is appropriate for your individual needs.
Essential Minerals: What They Do and Where to Find Them
Minerals are inorganic elements absorbed from food. Major minerals — those needed in larger amounts — include calcium, phosphorus, magnesium, sodium, potassium, and chloride. Trace minerals, needed in tiny amounts, include iron, zinc, selenium, iodine, and manganese, among others.
| Number of essential vitamins | 13 (NIH Office of Dietary Supplements) |
| Number of essential dietary minerals | Approximately 16 (General nutritional science consensus) |
| Most common nutrient deficiency worldwide | Iron deficiency (World Health Organization) |
| Vitamin produced by skin in sunlight | Vitamin D (NIH Office of Dietary Supplements) |
| Nutrient critical for early pregnancy | Folate (vitamin B9) (CDC folic acid guidance) |
| Vitamin found almost exclusively in animal foods | Vitamin B12 (NIH Office of Dietary Supplements) |
Calcium builds and maintains bones and teeth and plays a role in nerve transmission and muscle contraction. Dairy products are high-density sources, but fortified plant milks, tofu made with calcium sulfate, and leafy greens such as kale also contribute.
Iron is a component of hemoglobin, the protein that carries oxygen in red blood cells. Heme iron from meat and fish is absorbed more readily than non-heme iron from plant sources like lentils and spinach; pairing plant-based iron with vitamin C improves absorption.
Magnesium participates in more than 300 enzymatic reactions, including energy production and muscle relaxation. Nuts, seeds, whole grains, and legumes are reliable sources.
Iodine is essential for thyroid hormone production, which governs metabolism. Iodized salt and seafood are the main dietary sources in the US. Those avoiding both may need to consider their intake carefully with a healthcare provider's guidance.
When trying to understand where micronutrients fit on a food label, see our guide to reading a nutrition label.
This article is for general informational and educational purposes only. It is not a substitute for professional medical or dietary advice. Consult a qualified healthcare provider before making changes to your diet, especially if you have a medical condition or are considering supplements.