| Total essential vitamins | 13 (National Institutes of Health, Office of Dietary Supplements) |
| Fat-soluble vitamins | A, D, E, K |
| Highest dietary source of Vitamin B12 | Clams and beef liver (NIH Office of Dietary Supplements) |
| Calcium adequate intake (adult) | 1,000 mg/day (ages 19–50) (NIH Office of Dietary Supplements) |
| Vitamin D synthesis | Produced by skin exposed to UVB sunlight |
| Iron absorption booster | Vitamin C paired with plant-based iron sources (Academy of Nutrition and Dietetics) |
Why Vitamins and Minerals Matter
Vitamins and minerals are micronutrients — compounds your body needs in relatively small amounts but cannot function properly without. Unlike the macronutrients covered in our guide to protein, carbs, and fat, micronutrients don't provide calories. Instead, they act as the chemical tools that enable virtually every biological process: energy production, immune defense, bone maintenance, DNA repair, and more.
Deficiencies — even mild, subclinical ones — can affect mood, cognition, immunity, and long-term health. The good news is that for most healthy adults, a varied diet built around whole foods supplies most of these nutrients without the need for supplementation. This reference guide is designed to help you identify what each key nutrient does and where to find it on your plate.
This article is for general informational purposes only and does not constitute medical or nutritional advice. Consult a registered dietitian or qualified healthcare provider before making significant dietary changes or starting any supplement regimen.
| Total essential vitamins | 13 (National Institutes of Health, Office of Dietary Supplements) |
| Fat-soluble vitamins | A, D, E, K |
| Highest dietary source of Vitamin B12 | Clams and beef liver (NIH Office of Dietary Supplements) |
| Calcium adequate intake (adult) | 1,000 mg/day (ages 19–50) (NIH Office of Dietary Supplements) |
| Vitamin D synthesis | Produced by skin exposed to UVB sunlight |
| Iron absorption booster | Vitamin C paired with plant-based iron sources (Academy of Nutrition and Dietetics) |
Key Vitamins: Roles and Food Sources
Vitamins fall into two categories: fat-soluble (A, D, E, K) — stored in body fat and the liver — and water-soluble (C and the B vitamins) — not stored in significant amounts, meaning regular dietary intake matters more.
Micronutrients
Vitamins and minerals required by the body in small amounts to support normal physiological function. Unlike macronutrients, they provide no calories but are essential for health.
Fat-Soluble Vitamins
Vitamins A, D, E, and K, which are absorbed alongside dietary fat and stored in body fat and the liver. Because they accumulate, excessive intake from supplements can lead to toxicity.
Water-Soluble Vitamins
Vitamin C and the B vitamins, which dissolve in water and are not stored in large amounts. Excess is generally excreted in urine, so regular dietary intake is important.
Trace Minerals
Minerals such as iron, zinc, iodine, and selenium that the body needs in very small quantities. Despite low required amounts, deficiencies can have significant health effects.
Bioavailability
The proportion of a nutrient that the body actually absorbs and uses from a food or supplement. Bioavailability varies based on the nutrient's form, the food it comes from, and other compounds eaten alongside it.
Dietary Reference Intake (DRI)
A set of science-based reference values established by health authorities to guide adequate and safe nutrient intakes for different population groups. Includes the Recommended Dietary Allowance (RDA) and Tolerable Upper Intake Level (UL).
Fat-Soluble Vitamins
- Vitamin A: Supports vision (especially low-light), immune function, and skin integrity. Found in liver, dairy, eggs, and as beta-carotene in orange and leafy green vegetables.
- Vitamin D: Regulates calcium absorption and plays a role in immune function and muscle health. Synthesized by skin exposed to sunlight; dietary sources include fatty fish, egg yolks, and fortified foods.
- Vitamin E: Acts as an antioxidant, protecting cell membranes from oxidative damage. Found in nuts, seeds, vegetable oils, and leafy greens.
- Vitamin K: Essential for blood clotting and bone metabolism. Vitamin K1 is abundant in leafy greens; K2 is found in fermented foods and some animal products.
Water-Soluble Vitamins
- Vitamin C: Antioxidant, collagen synthesis, and immune support. Found in citrus fruits, bell peppers, strawberries, and broccoli.
- B Vitamins (B1–B12, Folate, Biotin, Pantothenic Acid): Collectively support energy metabolism, nervous system function, red blood cell production, and DNA synthesis. Sources vary widely — whole grains, legumes, meat, fish, eggs, and dark leafy greens are collectively strong contributors. Vitamin B12 is found almost exclusively in animal products, making it a nutrient of particular attention for those following plant-based diets.
- Folate (B9): Critical for DNA synthesis and cell division; especially important during pregnancy to support neural tube development. Leafy greens, legumes, and fortified grains are primary sources.
Key Minerals: Roles and Food Sources
Minerals are inorganic elements that support structural functions (bones, teeth), fluid regulation, nerve signaling, and enzyme activity. Macrominerals are needed in larger amounts; trace minerals (microminerals) are required only in tiny quantities but are no less important.
~42%
U.S. adults with vitamin D insufficiency
According to analysis of NHANES data published in Nutrition Research, approximately 42% of U.S. adults have insufficient vitamin D levels.
~10%
U.S. women of childbearing age with iron deficiency
The CDC estimates roughly 10% of U.S. women of childbearing age are iron deficient, making it one of the most common micronutrient deficiencies.
300+
Enzymatic reactions requiring magnesium
Magnesium acts as a cofactor in more than 300 enzyme systems, according to the NIH Office of Dietary Supplements.
Macrominerals
- Calcium: Primary structural mineral in bones and teeth; also involved in muscle contraction and nerve signaling. Sources include dairy products, fortified plant milks, tofu made with calcium sulfate, canned sardines, and leafy greens such as kale and bok choy.
- Magnesium: Involved in over 300 enzymatic reactions, including energy production and muscle function. Found in nuts, seeds, whole grains, legumes, and dark chocolate.
- Potassium: Maintains fluid balance, supports normal blood pressure, and is essential for muscle and heart function. Rich sources include bananas, potatoes, avocado, beans, and leafy greens.
- Sodium: Regulates fluid balance and nerve transmission. While it is an essential nutrient, most Americans consume more than current dietary guidelines recommend, largely from processed foods.
Key Trace Minerals
- Iron: Central to oxygen transport via hemoglobin. Heme iron from red meat and poultry is more readily absorbed than non-heme iron from plant sources; pairing plant iron with vitamin C can improve absorption.
- Zinc: Supports immune function, wound healing, and protein synthesis. Found in shellfish (especially oysters), red meat, legumes, nuts, and seeds.
- Iodine: Essential for thyroid hormone production, which regulates metabolism. Iodized table salt and seafood are primary sources in the U.S. diet.
- Selenium: Antioxidant functions and thyroid health. Brazil nuts are a famously concentrated source; seafood and whole grains also contribute.
To get the most from your meals, pair this reference with our weekly meal planning checklist to identify common nutritional gaps.
Practical Tips for Meeting Your Needs Through Food
The most research-supported approach to micronutrient adequacy is dietary diversity. No single food covers everything — but a plate that regularly rotates across vegetables, fruits, whole grains, legumes, nuts, seeds, and lean proteins comes close. When navigating packaged foods, our guide to reading ingredient lists can help you spot fortified options and cut through marketing claims.
If cooking from scratch feels like a barrier, it's worth noting that nutrient-dense eating doesn't require culinary expertise — see our practical nutrition guide for non-cooks for realistic strategies.
When Supplements May Be Warranted
Certain groups face higher risks of specific deficiencies and may benefit from targeted supplementation under professional guidance — for example, older adults (vitamin D, B12), people who are pregnant or planning pregnancy (folate, iron), and those following strict plant-based diets (B12, iron, zinc, iodine, omega-3s). Supplementation decisions should always be made with input from a healthcare provider or registered dietitian, as some nutrients can be harmful in excessive amounts.
Supplements Are Not a Substitute for a Varied Diet
While supplements can address specific, confirmed deficiencies, research generally does not support taking broad multivitamin supplements as a preventive measure for healthy adults with adequate diets. Whole foods deliver nutrients alongside fiber, phytochemicals, and other compounds that supplements cannot fully replicate. If you suspect a deficiency, ask your healthcare provider about testing before beginning supplementation.
This content is for general informational and educational purposes only. It does not replace the advice of a qualified healthcare professional. Individual nutritional needs vary and should be assessed by a licensed dietitian or physician.