| Total essential vitamins | 13 (Recognized by established nutritional science frameworks) |
| Fat-soluble vitamins | A, D, E, K |
| Water-soluble vitamins | C and 8 B vitamins |
| Most common vitamin deficiency globally | Vitamin D (Frequently cited in public health nutrition literature) |
| Vitamin B12 — highest risk groups | Older adults, vegans/vegetarians (NIH Office of Dietary Supplements) |
| Iron — absorption enhancer | Vitamin C improves non-heme iron uptake |
| Primary calcium storage site | Bones and teeth (~99% of body's calcium) (NIH Office of Dietary Supplements) |
What Are Micronutrients?
If macronutrients — carbohydrates, protein, and fat — are the body's fuel, then micronutrients are the spark plugs that keep the engine running. The term covers two broad categories: vitamins (organic compounds the body cannot make in sufficient quantities on its own) and minerals (inorganic elements obtained from food and water). Both are required in relatively small amounts compared to macronutrients, yet deficiencies in either category can meaningfully affect energy, immunity, bone health, and more.
Micronutrient
Vitamins and minerals required by the body in small amounts to support essential physiological functions. They do not provide calories but are critical for health.
Fat-soluble vitamin
Vitamins (A, D, E, K) that dissolve in fat and are stored in body tissues. Because they accumulate, very high intake — especially through supplements — can reach toxic levels.
Water-soluble vitamin
Vitamins (C and the B family) that dissolve in water and are not stored in large quantities. Excess is generally excreted, though some can be harmful at very high doses.
Heme iron
A form of iron found in animal muscle tissue (meat, poultry, fish) that is absorbed more efficiently by the body than non-heme iron.
Non-heme iron
Iron found in plant-based foods and fortified products. Its absorption is lower than heme iron but can be improved by consuming it alongside vitamin C.
Trace mineral
Minerals required in very small amounts — typically micrograms to a few milligrams per day — such as iron, zinc, iodine, and selenium.
Bioavailability
The proportion of a nutrient that the body actually absorbs and uses after ingestion. It varies by food source, preparation method, and individual factors.
Unlike macronutrients, micronutrients don't provide calories. Their roles are regulatory and structural — governing enzyme reactions, supporting nerve signaling, enabling oxygen transport, and maintaining fluid balance, among dozens of other functions. The most reliable way to meet micronutrient needs for most healthy adults is through a varied, food-first diet. For guidance on how nutrients are grouped in practical eating frameworks, see our plain-language dietary reference.
This article is for general informational and educational purposes only and is not a substitute for personalized medical or nutritional advice. Consult a qualified healthcare professional before making significant changes to your diet or taking supplements.
Key Vitamins: What They Do and Where to Find Them
| Total essential vitamins | 13 (Recognized by established nutritional science frameworks) |
| Fat-soluble vitamins | A, D, E, K |
| Water-soluble vitamins | C and 8 B vitamins |
| Most common vitamin deficiency globally | Vitamin D (Frequently cited in public health nutrition literature) |
| Vitamin B12 — highest risk groups | Older adults, vegans/vegetarians (NIH Office of Dietary Supplements) |
| Iron — absorption enhancer | Vitamin C improves non-heme iron uptake |
| Primary calcium storage site | Bones and teeth (~99% of body's calcium) (NIH Office of Dietary Supplements) |
Vitamins are divided into two groups based on how the body stores them:
- Fat-soluble vitamins (A, D, E, K) are stored in fatty tissue and the liver. Because they accumulate, excessive supplementation carries a risk of toxicity.
- Water-soluble vitamins (C and the B vitamins) are not stored in meaningful quantities; excess is generally excreted in urine, but very high doses of some — such as B6 — can still cause harm over time.
Fat-Soluble Vitamins
- Vitamin A
- Supports vision (especially in low light), immune defense, and skin integrity. Found in liver, dairy, eggs, and as beta-carotene in orange and dark leafy vegetables.
- Vitamin D
- Critical for calcium absorption and bone mineralization; also plays a role in immune function. Synthesized by skin exposed to UVB sunlight; dietary sources include fatty fish, egg yolks, and fortified foods.
- Vitamin E
- An antioxidant that helps protect cell membranes from oxidative damage. Found in nuts, seeds, vegetable oils, and spinach.
- Vitamin K
- Essential for blood clotting and bone metabolism. K1 comes mainly from leafy greens; K2 is found in fermented foods and some animal products.
Selected Water-Soluble Vitamins
- Vitamin C
- Supports collagen synthesis, wound healing, and immune function; also enhances non-heme iron absorption. Rich sources include citrus fruits, bell peppers, kiwi, and broccoli.
- B Vitamins (B1, B2, B3, B6, B9, B12)
- This family supports energy metabolism, red blood cell production, and nervous system function. B12 is found almost exclusively in animal products, making it a common concern for those following plant-based diets. Folate (B9) is especially important during early pregnancy — consult a healthcare provider about needs during this period.
Key Minerals: Roles and Food Sources
Minerals are categorized as macrominerals (needed in larger amounts, such as calcium and magnesium) or trace minerals (needed in tiny amounts, such as iron and zinc). Both groups are equally essential.
300+
Enzyme reactions involving magnesium
Magnesium's wide role in metabolism is well documented in established biochemistry literature.
~40%
US adults estimated low in vitamin D
Estimates vary by study methodology; figures from national nutrition surveys suggest a significant portion of Americans fall below recommended levels.
13
Essential vitamins recognized by nutritional science
Each plays at least one distinct physiological role that cannot be fully substituted by another nutrient.
- Calcium
- The most abundant mineral in the body, primarily stored in bones and teeth. Also involved in muscle contraction and nerve signaling. Sources: dairy products, fortified plant milks, tofu made with calcium sulfate, almonds, and bok choy.
- Iron
- Required for hemoglobin, the protein in red blood cells that carries oxygen. Heme iron (from meat and fish) is absorbed more readily than non-heme iron (from legumes, fortified grains, and spinach). Pairing non-heme iron sources with vitamin C improves absorption.
- Magnesium
- Involved in over 300 enzyme reactions, including energy production, muscle function, and DNA synthesis. Found in whole grains, legumes, nuts, seeds, and dark chocolate.
- Zinc
- Supports immune function, wound healing, and protein synthesis. Oysters are a particularly rich source; other sources include beef, pumpkin seeds, legumes, and whole grains.
- Potassium
- Helps regulate fluid balance, nerve signals, and blood pressure. Found in bananas, potatoes, avocados, beans, and leafy greens.
- Iodine
- Essential for thyroid hormone production, which governs metabolism. Iodized salt and seafood are primary sources in the US diet.
For practical guidance on putting micronutrient-rich foods together at meals, see Building a Balanced Plate. To understand how micronutrient content appears on food packaging, reading a nutrition label can help you translate the numbers.
Recognizing Deficiency and When to Seek Help
Supplements Are Not a Substitute for Diagnosis
Over-the-counter supplements can correct genuine deficiencies, but taking high doses without confirmed need can cause harm — some fat-soluble vitamins become toxic at elevated levels, and excess iron can damage organs over time. Before starting any supplement regimen, speak with a healthcare provider who can review your individual health status, diet, and any medications you take. Supplements are also not a replacement for a varied diet, which delivers nutrients alongside fiber, phytochemicals, and other compounds that work together.
Deficiency symptoms are often non-specific — fatigue, for instance, can be associated with low iron, vitamin D, B12, or magnesium, among other causes. Common signs associated with specific shortfalls include:
- Iron deficiency: Fatigue, pale skin, brittle nails, reduced exercise tolerance.
- Vitamin D deficiency: Bone pain, muscle weakness, low mood (emerging research); more common in people with limited sun exposure.
- Vitamin B12 deficiency: Tingling in hands or feet, fatigue, memory difficulties; higher risk in older adults and those avoiding animal products.
- Calcium deficiency: Muscle cramps, dental problems; long-term inadequacy contributes to reduced bone density.
- Iodine deficiency: Thyroid enlargement (goiter), fatigue, difficulty concentrating.
This list is illustrative, not diagnostic. Many conditions share overlapping symptoms. If you suspect a deficiency, a healthcare provider can assess your diet history and order appropriate bloodwork. Do not self-diagnose or begin high-dose supplementation without professional guidance, as some vitamins and minerals can cause harm when taken in excess.