More than half of all Americans take at least one daily vitamin supplement. It’s easy to see why: the claims of weight loss, pain relief, longer life and better health make supplements extremely appealing. But are supplements really all they’re cracked up to be?

Vitamin supplements are a billion-dollar industry in the United States, with multivitamins being the most popular. Despite their widespread use, the U.S. Food and Drug Administration (FDA) doesn’t review the safety or efficacy of supplements before they hit the market. That’s why it’s always a good idea to research claims, read ingredients and, of course, talk to your doctor before trying a new supplement.

Below you’ll find an introduction to the world of vitamin supplements, recommendations on which supplements you may want to take based on your situation, and an answer to the question, “Do vitamins work?”

What are vitamins?

Vitamins are the nutrients that your body needs to be healthy and function at its best. We can usually get all our necessary nutrients from natural sources, like plants, animal products and sunlight. A diet full of colorful fruits and vegetables, lean meats, low-fat dairy products and whole grains is our best source of vitamins.

When we don’t get enough nutrients from the food we eat for whatever reason, we can take vitamin supplements to help fill in the gaps.

Are vitamins necessary?

We need vitamins, we just don’t always need vitamin supplements. Multiple conditions and different diets can result in a vitamin deficiency, or the lack of a certain vitamin to the extent that it may affect our health.

Vitamin supplements can help fill in these nutritional gaps, but it’s important to ask your doctor about any possible vitamin deficiencies you may have before starting supplements. Think of supplements like you do other medicines. We only start taking medications because our doctor prescribes them for our health.

Vitamins from food are best

The best approach to increasing or monitoring your vitamin intake is to focus on a healthy, balanced diet, from which you can get all the vitamins you need. Your body is better able to absorb and use vitamins that come from food. And it’s better for long-term health. Recent studies have shown that vitamins from food are more likely to prevent cancer, heart disease and early mortality.

Working with a dietitian is a great way to make sure you’re eating a diet that is full of the healthy vitamins you need.

Vitamins from supplements, if needed

You don’t typically need supplements if you are eating a healthy, balanced diet, but this isn’t always enough. Illness and age can interfere with the proper absorption of vitamins in your body. Or you may be following certain dietary restrictions due to health or personal beliefs. In these cases, you could take supplements, but it’s always best to ask your doctor before adding any supplement to your daily routine.

Supplements come in different forms and certain types are better for certain situations. When you decide to take a supplement, you have choices when it comes to how you take it. Tablets and caplets are the most effective form, but you can also try powders, gummies, liquids and soft gels.

Are multivitamins good for you?

While a multivitamin might seem like a great way to get all your vitamins in one convenient form, studies have shown they can’t prevent chronic disease, cognitive decline, heart attack or stroke the same way a good diet can.

With multivitamins, you can’t always control how much of each vitamin you ingest or target specific deficiencies. Perhaps you need more calcium, but your multivitamin contains vitamin E as well. Vitamin E is one type of vitamin that can be harmful when consumed in high doses. You could inadvertently build up a dangerous level of vitamin E in your body while trying to address low levels of calcium.

In addition, certain vitamin supplements can interact negatively with prescription medicine. Before taking any multivitamin, talk to your doctor about what is right for you.

Can vitamins be trusted?

There’s a lot of information swirling around about supplements, and it can be hard to separate fact from fiction.

As we said above, the FDA doesn’t regulate vitamin supplements like they do prescription medicines. There are certain rules set by the FDA that supplement manufacturers are expected to follow, including the claims they can make on their labels. Any benefits listed on supplement bottles, websites or advertising must be followed by, “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.”

Supplements can be sold without FDA approval. But if a supplement is found to be unsafe after it has already been on the market, the FDA can ask that it be recalled. When it comes to supplements, it’s a good idea to do your own research on ingredients and manufacturer practices. Your doctor is an excellent resource if you have questions about vitamin supplements.

What are the most important vitamins?

There are several vitamins and minerals that are considered the most essential to bodily function and good health.

Vitamins can be fat soluble or water soluble, depending on how they act in the body. Water-soluble vitamins, which includes vitamin C and B vitamins, dissolve in water and are flushed from the body in our urine after only a short amount of time. Fat-soluble vitamins dissolve in fat and the body stores them for extended periods of time. This creates the risk of toxicity – or having a potentially harmful amount of any one vitamin in the body – when supplementing vitamins A, D, E and K.

Vitamin A

An adequate amount of vitamin A in our diet supports our eye health and improves our vision in dark conditions. Vitamin A also keeps our immune system strong and aids the growth of new cells in our bones and other organs.

We get vitamin A from food in the form of beta-carotenes, which our body then turns into vitamin A. Beta-carotene is a type of natural pigment, so colorful fruits and vegetables, like carrots, sweet potatoes, tomatoes, leafy greens, cantaloupe and mango, are great sources of vitamin A.

Vitamin C

While vitamin C isn’t quite the immune system superhero its reputation suggests, it does have other amazing benefits. Vitamin C helps us heal wounds faster and fight infection, while also being a major ingredient in the production of collagen, the protein that holds the body together. Vitamin C deficiency causes a disease known as scurvy, historically common among sailors during lengthy sea voyages.

Citrus fruits are a major source of vitamin C, as are strawberries, tomatoes, potatoes, bell peppers, chili peppers, parsley, broccoli, cauliflower, Brussels sprouts and cabbage.

Vitamin D

Vitamin D has multiple roles in the body – reducing inflammation, curbing the growth of cancer cells, suppressing infection – but its most important job is that of a helper. We need vitamin D to help us absorb calcium and phosphorus, two minerals that make up strong, healthy bones. Prolonged vitamin D deficiency can lead to osteoporosis and, among children, a rare disease called rickets.

When our skin is exposed to UV rays from sunlight, the body naturally produces vitamin D. That’s why it’s so important to get at least 10 minutes of sunshine every day. Dietary sources of vitamin D include fatty fish like salmon, swordfish, tuna and sardines, and it’s also added to orange juice and many dairy products.

Vitamin E

Vitamin E supports the immune system while keeping your eyes, heart and brain healthy. It’s also an antioxidant, meaning it can protect our cells from damaging “free radicals,” or unstable particles found in toxic chemicals, tobacco smoke and alcohol.

You can find vitamin E in many types of plant-based oils, nuts and seeds, in addition to fruits and vegetables. To get more vitamin E, try eating more peanuts and peanut butter, sunflower and canola oil, olive oil, spinach, collard greens, pumpkin, red bell pepper, asparagus, mango and avocado.

Vitamin K

Vitamin K helps your body form good blood clots, the kind that are essential to wound healing. People taking blood thinners are often recommended to increase their intake of vitamin K. Vitamin K also assists in the creation of new bone tissue.

Some major sources of vitamin K are vegetables and leafy greens like spinach, kale, Brussels sprouts, cabbage, broccoli, collard greens and lettuce, but it can also be found in plant-based oils like soybean and canola oil.

B vitamins

The B vitamins are key for several functions throughout the body. They help our cells perform tasks like turning carbohydrates into energy, absorbing fats and proteins, and creating new cells. Vitamin B9, also known as folate and folic acid, can help prevent birth defects when taken by pregnant women.

B vitamins also act like antioxidants, protecting our cells from damaging substances we encounter as we move through the world. There are eight B vitamins:

  • B1 (thiamin)
  • B2 (riboflavin)
  • B3 (niacin)
  • B5 (pantothenic acid)
  • B6 (pyridoxine)
  • B7 (biotin)
  • B9 (folate/folic acid)
  • B12 (cobalamin)

We can get a variety of B vitamins from eating beef, seafood, poultry, eggs, liver, oats, mushrooms, avocado, milk and leafy green vegetables.

Calcium

Calcium is a mineral that keeps our bones and teeth healthy and strong. It also supports healthy muscle function. Most of our calcium is collected in our bones, and our body will draw on this store when we don’t have enough calcium in other areas, like our blood. Consuming enough calcium prevents our body from having to “borrow” calcium from our bones.

We get a lot of calcium from dairy, including cheese, yogurt and fortified alternative milks (almond, soy), but other sources are winter squash, tofu, almonds, edamame, fish that have edible bones (like canned sardines or salmon), and leafy greens like spinach and kale.

Iron

Iron is a mineral that contributes to the production of new red blood cells. These red blood cells distribute oxygen throughout our body. It’s also important in children’s healthy growth and development. When you have low levels of iron, you can develop a condition known as iron-deficiency anemia. Being anemic means you don’t have enough red blood cells or your red blood cells aren’t working properly, and your body isn’t getting the oxygen it needs. Women who experience heavy periods may want to consider increasing their iron intake.

Iron can be found in red meat, poultry, seafood, beans, lentils, spinach, nuts and seeds. Many types of cereals and breads are also fortified with iron.

Magnesium

Magnesium is a mineral that contributes to the health of our bones and muscles, and can help prevent type 2 diabetes, heart disease, Alzheimer’s disease and migraines. Some recent studies suggest that magnesium may even ease symptoms of anxiety, but more research is needed.

Magnesium is concentrated in leafy greens like spinach, but it can also be found in pumpkin seeds, almonds, cashews, legumes like edamame and black beans, tofu, whole grains, bananas and avocado.

Who should take vitamins?

Certain diets and life circumstances may create vitamin deficiencies. In these cases, supplements can be a useful tool to maintain all-around health. If you fall into any of the following groups, ask your doctor if you could benefit from taking supplements.

Vegans and vegetarians

Because we get so many of our vitamins from fruits and vegetables, most people can still enjoy a well-rounded, nutrient-rich diet without eating meat, eggs or dairy. However, if you’re a vegetarian or vegan, you may want to ask your doctor about supplementing vitamin B12, as it’s found mostly in animal products. Vegans can also opt to take vitamin D supplements, as many of the foods fortified with vitamin D are dairy-based.

Pregnant women

During pregnancy, the body requires a greater intake of many nutrients to be able to support a growing fetus. Your doctor can recommend a prenatal vitamin that contains all the vitamins and minerals you need for your unique pregnancy. They can also help you develop a pregnancy diet that works for you.

Folic acid (vitamin B9), vitamin D, iron, calcium and iodine are especially important during this time to support healthy fetal development and prevent birth defects.

Older adults

Vitamin deficiencies in the U.S. are rare. But sometimes, due to certain medications, illness, surgery or other conditions, your body doesn’t have enough of some vitamins and can’t get the amount it needs through food. You may want to talk to your doctor about incorporating supplements into your care plan.

How do I tell if I need to take vitamins?

Low levels of certain vitamins in your body can cause you to develop diseases like scurvy and anemia. However, these are not common in the U.S., where we have access to a range of healthful and vitamin-enriched foods. Still, it’s good to be aware of the signs of various vitamin deficiencies, so you can talk to your doctor and supplement as needed.

Some indicators that you may be experiencing a vitamin deficiency:

These symptoms don’t always indicate a vitamin deficiency, as they are common in many other conditions.

On the flip side, some vitamin deficiencies have no symptoms. Whatever the case, talk to your doctor if you think you may have a vitamin deficiency. They can perform a blood test to check your vitamin levels.

Can you take too many vitamins?

Yes, it is possible to overdose on vitamins, but it’s rarely life threatening. When one or more vitamins has accumulated to excessive levels in your body, this is called toxicity. Signs of toxicity vary depending on the vitamin, but can include symptoms related to your skin, digestive system, or neurological health (such as migraines, irritability and confusion).

In order to avoid toxicity, you will want to have your vitamin levels checked by your doctor before you begin taking a supplement. They can see if you do in fact have a deficiency. If you start taking a vitamin that you’re not deficient in, it can result in toxicity fairly quickly.

Talk to your doctor about vitamins

Vitamin supplements are not black and white. They can be a helpful tool, if used responsibly and with a doctor’s recommendation. But it’s best to fulfill your vitamin needs the natural way – through a balanced diet.

If you’re curious about supplements or think you may have a vitamin deficiency, always start with a visit to your doctor.