What Vitamins and Minerals Really Do in Your Body

Food gives us energy, but just as important, it delivers vitamins and minerals. There is essentially no bodily function that doesn’t depend on at least one of these compounds, roughly 30 of which are considered crucial. They help our hearts beat and our lungs breathe. They enable our bodies to build new muscle, skin and bone cells. They allow nerves to send signals to the brain and the immune system to fight invaders. We literally can’t live without them.

The difference between vitamins and minerals is that the former are organic—made by a plant or animal—and the latter are not. We absorb vitamins directly from the plants and animals we eat. We get minerals, which come from rocks, dirt or water, sometimes from the environment and sometimes from living things we eat that absorbed them before they died.

“Vitamins and minerals work in wild and wondrous ways, some of which we understand, many of which we’re still trying to understand,” says Howard Sesso, associate director of the division of preventive medicine at Brigham and Women’s Hospital and medical editor of the Making Sense of Vitamins and Minerals report from Harvard Medical School. “And there’s tremendous variation in how we all consume, digest, absorb and utilize the nutrients in a particular food we’re eating.”

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Key Functions • Listed here are the main known uses of different nutrients, although scientists suspect there are many that are undiscovered. Furthermore, vitamins and minerals often interact with one another and help to promote the reactions of other nutrients.

CATEGORY: Water-Soluble Vitamins

These vitamins can dissolve in water.

  • Vitamin B1 (thiamin) • Helps to turn food into energy. Promotes skin, hair, muscle and brain health. Critical for nerve function.Rich Food Sources: Pork, brown rice, soy milk, watermelon, acorn squash

  • Vitamin B2 (riboflavin) • Helps to turn food into energy. Boosts skin, hair, blood and brain health.Rich Food Sources: Meat, milk, eggs, yogurt, cheese, green leafy vegetables

  • Vitamin B3 (niacin, nicotinic acid, nicotinamide) • Helps to turn food into energy. Essential for healthy skin, blood cells, brain and nervous system.Rich Food Sources: Meat, poultry, fish, whole grains, mushrooms, potatoes, peanut butter

  • Vitamin B5 (pantothenic acid) • Helps to turn food into energy. Helps to produce lipids, neurotransmitters, steroid hormones and hemoglobin.Rich Food Sources: Chicken, egg yolk, whole grains, broccoli, mushrooms, avocados

  • Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine) Metabolizes amino acids and helps cells replicate. Helps to produce red blood cells and neurotransmitters essential for brain function.Rich Food Sources: Meat, fish, poultry, legumes, tofu, potatoes, bananas, watermelon

  • Vitamin B7 (biotin) • Helps to convert food into energy and make glucose. Helps to build and break down some fatty acids. Promotes bone and hair health.Rich Food Sources: Whole grains, organ meats, egg yolks, soybeans, fish

  • Vitamin B9 (folate, folic acid, folacin) • Metabolizes amino acids and helps cells multiply. Vital for new cell creation. Helps to prevent brain and spine birth defects when taken early in pregnancy. Rich Food Sources: Asparagus, okra, spinach, turnip greens, broccoli, legumes, orange juice, tomato juice

  • Vitamin B12 (cobalamin, cyanocobalamin) • Metabolizes amino acids and helps cells multiply. Protects nerves and encourages their growth. Helps to build red blood cells and DNA.Rich Food Sources: Meat, poultry, fish, milk, cheese, eggs

  • Vitamin C (L-ascorbic acid) • Makes collagen, as well as the neurotransmitters serotonin and norepinephrine. Works as an antioxidant. Boosts the immune system.Rich Food Sources: Fruits (especially citrus), potatoes, broccoli, bell peppers, spinach, strawberries, tomatoes, brussels sprouts

CATEGORY: Water-Soluble Nutrient

Choline is organic and water-soluble, but it’s not classified as either a vitamin or a mineral. It’s somewhat similar to B vitamins.

  • Choline (formerly called vitamin B4 ) • Helps to make the neurotransmitter acetylcholine. Aids in metabolizing and transporting fats.Rich Food Sources: Milk, eggs, liver, salmon, peanuts

CATEGORY: Fat-Soluble Vitamin

These organic nutrients dissolve in fats and oils and are mostly found in fat tissue and the liver.

  • Vitamin A (retinoids—preformed vitamin A, beta carotene—converts to vitamin A) • Important for vision, cell health, bone formation and immune system function. • Rich Food Sources: Liver, fish, eggs, sweet potatoes, carrots, pumpkins, squash, spinach, mangoes, turnip greens

  • Vitamin D (calciferol, cholecalciferol—vitamin D3 , ergocalciferol—vitamin D2 ) • Helps to keep calcium and phosphorus at normal levels in the blood. Assists in forming teeth and bones. • Rich Food Sources: Fortified milk or margarine, fortified cereals, fatty fish (Your body also uses sunlight to make vitamin D.)

  • Vitamin E (alpha-tocopherol) • Acts as an antioxidant, aids the immune system and supports vascular health. • Rich Food Sources: Vegetable oils, wheat germ, leafy green vegetables, whole grains, nuts

  • Vitamin K (phylloquinone—vitamin K1 , menaquinones—vitamin K2 ) • Aids in bone formation. Activates proteins and calcium essential for blood clotting. • Rich Food Sources: Cabbage, liver, eggs, milk, spinach, broccoli, sprouts, kale, collards, other green vegetables

CATEGORY: Major Mineral

The body needs relatively large amounts of these minerals, although too much of one can sometimes block the absorption of another.

  • Calcium • Helps to build and protect teeth and bones. Aids with muscle function, blood clotting, nerve impulse transmission, hormone secretion and enzyme activation. • Rich Food Sources: Yogurt, cheese, milk, tofu, sardines, salmon, fortified juices, broccoli, kale

  • Chloride • Balances fluids in the body and forms part of the stomach acid, which helps to digest food. • Rich Food Sources: Salt (sodium chloride), soy sauce, processed foods

  • Magnesium • Necessary for chemical reactions in the body. Aids in muscle contraction, blood clotting and regulation of blood pressure. Helps to build bones and teeth. • Rich Food Sources: Spinach, broccoli, legumes, cashews, sunflower and other seeds, halibut, whole wheat bread, milk

  • Phosphorus • Builds and protects bones and teeth. Forms a part of DNA and RNA. Helps to convert food into energy. Helps to move nutrients into and out of cells. • Rich Food Sources: Milk and dairy products, meat, fish, poultry, eggs, liver, green peas, broccoli, potatoes, almonds

  • Potassium • Helps to balance fluids in the body. Helps to maintain a steady heartbeat and send nerve impulses. Required for muscle contractions. • Rich Food Sources: Meat, milk, fruits, vegetables, grains, legumes

  • Sodium • Helps to balance fluids in the body. Helps to send nerve impulses. Needed for muscle contractions. Impacts blood pressure. • Rich Food Sources: Salt, soy sauce, processed foods, vegetables

  • Sulfur • Helps to shape and stabilize protein structures. Necessary for healthy hair, skin and nails. • Rich Food Sources: Protein-rich foods, such as meat, fish, poultry, nuts, legumes

CATEGORY: Trace Mineral

Only small quantities of these are necessary for the body, but they are as essential as the major minerals.

  • Chromium • Boosts insulin activity, helps to maintain normal blood glucose levels, and is required to free energy from glucose. • Rich Food Sources: Meat, poultry, fish, eggs, potatoes, some cereals, nuts, cheese, brewer’s yeast

  • Copper • Important for iron metabolism and the immune system. Helps to make red blood cells. • Rich Food Sources: Liver, shellfish, nuts, seeds, whole-grain products, beans, prunes, cocoa, black pepper

  • Fluoride • Strengthens bones and stimulates new bone formation. Prevents tooth decay. • Rich Food Sources: Fluoridated water, toothpaste with fluoride, marine fish, teas

  • Iodine • Necessary for synthesizing thyroid hormones, which help to maintain body temperature and influence nerve and muscle function. • Rich Food Sources: Iodized salt, processed foods, seafood

  • Iron • Helps to transport oxygen through the body. Required for chemical reactions in the body and for making amino acids, collagen, neurotransmitters and hormones. • Rich Food Sources: Red meat, poultry, eggs, fruits, green vegetables, fortified bread and grain products

  • Manganese • Helps to form bones and metabolize amino acids, cholesterol and carbohydrates. • Rich Food Sources: Fish, nuts, legumes, whole grains, tea

  • Molybdenum • Forms part of several enzymes, including one that protects against potentially deadly neurological damage in infants. • Rich Food Sources: Legumes, nuts, grain products, milk

  • Selenium • Acts as an antioxidant and helps to regulate thyroid hormone activity. • Rich Food Sources: Organ meats, seafood, walnuts, sometimes plants (depends on soil content), grain products

  • Zinc • Helps to form enzymes and proteins and to build new cells. Frees vitamin A from storage in the liver. Vital for the immune system, taste, smell and wound healing. • Rich Food Sources: Red meat, poultry, oysters and some other seafood, fortified cereals, beans, nuts

Delicate Balance

When we eat too much of one vitamin or mineral, it can cause the loss of another. For instance, an excess of sodium will deplete calcium because these nutrients bind together, causing the body to excrete them both when it flushes out the sodium.

Getting Enough

In the U.S., nutrition deficiencies are relatively rare, although malnutrition is increasing, especially among older age groups. The most common deficiencies are of vitamin B6, iron and vitamin D. Of all the vitamins and minerals, Americans are least likely to be deficient in vitamin A, vitamin E and folate (B9).

Beneficial combinations

Some nutrients work best as a team. Vitamin D helps us absorb calcium, for instance, and potassium encourages the excretion of excess sodium. Folate (B9) is best absorbed if B12 is around, and the two work together to help cells divide and multiply.


The recommended daily intake depends on age, sex, and many other factors. Dosage icons here are purposefully large to show the big-picture variation between different nutrients.

Graphic shows recommended and maximum daily intake of vitamins and minerals for adults. Water-soluble and fat-soluble vitamins have a wide range of recommended doses. Major mineral recommendations are relatively high: Trace mineral recommendations are lower.
Graphic shows what human body parts different vitamins and minerals are stored in. The liver, bones and teeth, muscles and blood top the list for sheer number of different nutrients they hold for later use.

For more information: Dietary Supplement Fact Sheets, National Institutes of Health; Making Sense of Vitamins and Minerals, a special health report by the editors at Harvard Health Publishing in consultation with Howard D. Sesso, 2022.

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