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Q. How do I know if I need a dietary supplement?
A. Many products are marketed as dietary supplements, and it is important to remember that supplements include not only vitamins and minerals, but also herbs and other botanicals, probiotics, fish oil, and other substances.
Some supplements may help ensure that you get adequate amounts of essential nutrients or help promote optimal health and performance if you do not consume a variety of foods, as recommended by MyPlate and the Dietary Guidelines for Americans.
However, dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.
Do not self-diagnose any health condition. Work with your health care provider to determine how best to achieve optimal health. Also check with your health care provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.
Q. Where can I find out how much of each vitamin and mineral I need?
A. To get a list of all vitamins and minerals and how much you need, check out the free online tool from the U.S. Department of Agriculture. Just input a few pieces of information about yourself including your age, height, and weight. You also can get a list of your daily calorie, protein, and other nutritional needs. Keep in mind that the amounts of vitamins and minerals you need include everything you get from food and beverages—you may or may not need a dietary supplement to achieve these amounts. Talk with your health care provider to help you determine which supplements, if any, might be valuable for you. For more detailed information about each vitamin and mineral, see vitamin and mineral fact sheets.
In addition, you can get good sources of information on eating well from the Dietary Guidelines for Americans and MyPlate.
Q. How can I get more information about a particular dietary supplement such as whether it is safe and effective?
A. Scientific evidence supporting the benefits of some dietary supplements (for example, vitamins and minerals) is well established for certain health conditions, but others need further study.
Research studies in people to prove that a dietary supplement is safe are not required before the supplement is marketed, unlike for drugs. This is due to the way dietary supplements are regulated by the U.S. Food and Drug Administration (FDA). It is the responsibility of dietary supplement manufacturers/distributors to ensure that their products are safe and that their label claims are truthful and not misleading. If the FDA finds a supplement to be unsafe once it is on the market, only then can it take action against the manufacturer and/or distributor, such as by issuing a warning or requiring the product to be removed from the marketplace.
The manufacturer does not have to prove that the supplement is effective, unlike for drugs. The manufacturer can say that the product addresses a nutrient deficiency, supports health, or reduces the risk of developing a health problem, if that is true. If the manufacturer does make a claim, it must be followed by the statement “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.”
Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions. Supplements should not replace prescribed medications or the variety of foods important to a healthful diet.
Do not self-diagnose any health condition. Work with your health care provider to determine how best to achieve optimal health. Also, check with your health care provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.
In addition to talking with your health care provider about dietary supplements, you can search online for information about a particular supplement. It is important to ensure that you obtain information from reliable sources such as:
Q. Where can I find information about the use of dietary supplements for a particular health condition or disease?
A. Scientific evidence supporting the benefits of some dietary supplements (for example, vitamins and minerals) is well established for certain health conditions, but others need further study. Whatever your choice, supplements should not replace prescribed medications or the variety of foods important to a healthy diet.
Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. In some cases, dietary supplements may have unwanted effects, especially if taken before surgery or with other dietary supplements or medicines, or if you have certain health conditions.
Do not self-diagnose any health condition. Work with your health care provider to determine how best to achieve optimal health. Also, check with your health care provider before taking a supplement, especially if you take any medicines or other dietary supplements or if you have any health conditions.
In addition to talking with your health care provider about dietary supplements for a particular health condition or disease, you can search on-line for information. It is important to ensure that you obtain information from reliable sources such as:
Q. What does the Supplement Facts label on a dietary supplement tell me?
A. All products labeled as dietary supplements carry a Supplement Facts label that is similar to the Nutrition Facts label found on food products. It lists the active ingredients and their amounts, plus other added ingredients like fillers, binders, and flavorings. It also gives a suggested serving size, but you and your health care provider might decide that a different amount is more appropriate for you.
In the Supplement Facts label, the amounts of vitamins, minerals, and other nutrients like dietary fiber are listed as a percentage of the Daily Value (%DV). Each nutrient has one DV that applies to all people aged 4 and older. For example, the DV for vitamin C is 90 milligrams (mg) and the DV for the B-vitamin biotin is 30 micrograms (mcg).
The %DV allows you to see how much a product contributes to your approximate daily needs for that nutrient. For example, if a supplement provides 50% of the DV for calcium, it contributes about half of your daily needs for calcium.
The U.S. Food and Drug Administration (FDA) has a webpage that describes the Nutrition Facts label and DV in more detail.
Q. What is the difference between the RDA and DV for a vitamin or mineral?
A. Many terms are used when referring to either the amount of a particular nutrient (such as calcium or vitamin D) you should get or the amount in a food or dietary supplement. The two most common are the Recommended Dietary Allowance (RDA) and the Daily Value (DV). These terms can be confusing.
RDAs are recommended daily intakes of a nutrient for healthy people. They tell you how much of that nutrient you should get on average each day. RDAs are developed by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine. They vary by age, sex, and whether a woman is pregnant or breastfeeding; so there are many different RDAs for each nutrient.
DVs, established by the U.S. Food and Drug Administration (FDA), are used on food and dietary supplement labels. For each nutrient, there is one DV for all people ages 4 years and older. Therefore, DVs aren’t recommended intakes, but suggest how much of a nutrient a serving of the food or supplement provides in the context of a total daily diet. DVs often match or exceed the RDAs for most people, but not in all cases.
DVs are presented on food and supplement labels as a percentage. They help you compare one product with another. As an example, the %DV for calcium on a food label might say 20%. This means it has 260 milligrams (mg) of calcium in one serving because the DV for calcium is 1,300 mg/day. If another food has 40% of the DV for calcium, it’s easy to see that it provides much more calcium.
The Dietary Supplement Label Database has a webpage that lists the DVs for all nutrients.
Q. What are the upper limits for vitamins and minerals?
A. Our bodies need vitamins and minerals for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.
Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.
Which vitamins and minerals fall into which category? Here’s the breakdown:
Stay under the UL each day for these nutrients to avoid health problems unless your health care provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal. The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.
These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.
Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.
Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.
These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your health care provider recommends it.
Have more questions? See fact sheets on vitamins and minerals for details about the recommended amounts and ULs.
Q. Where can I find free, accurate information about vitamins, minerals, herbs, and other dietary supplements?
A. Good places to start are the ODS dietary supplement fact sheets, which provide helpful information about dietary supplement ingredients including recommended amounts, health effects, safety, and medication interactions. Many of the ODS fact sheets come in three versions—the easy-to-read Consumer version in both English and Spanish, and the more detailed Health Professional version. Read them online or print a copy. In addition, Herbs at a Glance fact sheets from the National Center for Complementary and Integrative Health (NCCIH) provide basic information on specific herbs and botanicals—common names, uses, potential side effects, and resources for more information.
Q. Where can I find published scientific studies about dietary supplements?
A. You can search for medical and scientific studies on specific dietary supplement ingredients using PubMed. PubMed is a database of the National Library of Medicine that provides access to over 35 million journal citations for biomedical literature from MEDLINE, life science journals, and online books.
Q. Where can I find out how much of each vitamin and mineral I need?
A. To get a list of all vitamins and minerals and how much you need, check out the free online tool from the U.S. Department of Agriculture. Just input a few pieces of information about yourself including your age, height, and weight. You also can get a list of your daily calorie, protein, and other nutritional needs. Keep in mind that the amounts of vitamins and minerals you need include everything you get from food and beverages—you may or may not need a dietary supplement to achieve these amounts. Talk with your health care provider to help you determine which supplements, if any, might be valuable for you. For more detailed information about each vitamin and mineral, see vitamin and mineral fact sheets.
In addition, you can get good sources of information on eating well from the Dietary Guidelines for Americans and MyPlate.
Q. I try to eat right, but sometimes I don’t succeed. How do I know if I should take a multivitamin supplement?
A. In most cases it’s best to get nutrients from food first, if you can, before taking supplements. Multivitamin/mineral supplements (MVMs) cannot take the place of eating a variety of foods that are important to a healthy diet. But people who don’t get enough vitamins and minerals from food alone, are on low-calorie diets, have a poor appetite, or avoid certain foods (such as strict vegetarians and vegans) might consider taking an MVM. Health care providers might also recommend MVMs to patients with certain medical problems. In addition, certain vitamin and mineral supplements are recommended in specific circumstances as discussed below.
See fact sheet on MVMs which discusses what types of MVMs are available and possible effects of MVMs on health, and provides guidance on which kind of MVM to choose.
Most research suggests that getting recommended intakes of vitamins and minerals from food—and dietary supplements as needed—promotes health. Our fact sheet points out that some people might benefit from taking certain nutrients found in MVMs. For example:
Keep in mind that manufacturers add some of the vitamins and minerals found in dietary supplements to a growing number of foods, including breakfast cereals and beverages. As a result, you may be getting more of these nutrients than you think, and more might not be better. Taking more than you need is always more expensive and can increase your risk of side effects.
You may have read about some recent studies suggesting that taking an MVM—or nutrients such as folic acid, copper, and iron—is linked to an increased risk of death. For example, in one study, calcium was the only nutrient that reduced the risk of death. Because the participants in this study were almost all white postmenopausal women, the results cannot be applied to men, younger women, or to people of different ethnicities or races. In addition, the study was not a cause and effect study, so it cannot prove that taking supplements results in dying earlier. Most other studies don’t find a link between taking an MVM or other nutrient dietary supplement and increased risk of death.
To get a personalized list of your nutrient needs, you can use the interactive dietary reference intake tool from the U.S. Department of Agriculture (USDA).
Q. I am overwhelmed by the multivitamin choices at my store. Which product should I buy?
A. Talk with your health care provider for advice. Your provider can help you find an appropriate multivitamin.
Consider choosing a multivitamin designed for your age, sex, and whether you are pregnant or breastfeeding. The recommended amounts of vitamins and minerals differ from person to person, and many multivitamin manufacturers take this into account when formulating products. For example, multivitamins for women usually have more iron and folic acid than those for men. Multivitamins for older adults usually provide more calcium and vitamins D and B12, and less iron than those for younger adults. Prenatal multivitamins often provide vitamin A as beta-carotene and have higher amounts of iron. Most children’s multivitamins have smaller amounts of many nutrients.
See vitamin and mineral fact sheets list for the recommended intakes for all nutrients based on your age, sex, and whether you are pregnant or breastfeeding.
Want to compare products from home? Use Dietary Supplement Label Database to search for and compare thousands of dietary supplement products on the market, including many multivitamins.
Q. Do multivitamins have any safety concerns?
A. Not for most people. Taking a basic multivitamin is unlikely to harm your health, assuming the product is properly manufactured. Most products contain reasonable amounts of vitamins and minerals and can help ensure you get enough essential nutrients without causing any harm.
However, some vitamins and minerals can be harmful if you get too much, that is, more than the upper limits. So, check product labels and don’t “double up” on multivitamins or other dietary supplements unless your health care provider has told you to do so. And keep in mind that some foods are fortified with extra vitamins and minerals. These also count toward the upper limits. Our vitamin and mineral fact sheets list the upper limits for all nutrients.
If you smoke or used to smoke, you should avoid multivitamins that have high amounts of beta-carotene or vitamin A. Studies show that smokers who take more than 20 milligrams (mg) a day of beta-carotene or more than 7,500 micrograms (mcg) a day of vitamin A might have a higher risk of lung cancer. Most multivitamins have lower amounts of these ingredients, but check labels to be sure.
If you are pregnant, don’t get too much vitamin A—more than about 2,800 mcg a day—because it increases the risk of birth defects. This is not a concern for beta-carotene, the form of vitamin A in plant foods such as carrots and some dietary supplements.
For more information on multivitamins, see multivitamin/mineral fact sheet.
Q. I know that carrots are healthy and have lots of vitamin A. But I’ve also heard that too much vitamin A can be dangerous, so do I need to limit how many carrots I eat?
A. Vitamin A can be toxic at high doses, causing liver damage and birth defects if a woman is pregnant. However, this applies only to the form of vitamin A—called preformed vitamin A or retinol—that is found in foods from animals, such as beef liver, milk, milk products, and some dietary supplements.
Plant foods, such as carrots, spinach, and red peppers, contain a form of vitamin A called beta-carotene. Consuming high amounts of beta-carotene can turn your skin yellow-orange, but this condition is harmless. Beta-carotene does not cause birth defects or the other more serious effects caused by getting too much preformed vitamin A.
So enjoy plenty of carrots and other fruits and vegetables without worrying about getting too much vitamin A. Have more questions? See fact sheet on vitamin A.
Q. I eat a lot of carrots and I know that they have beta-carotene. I have read that beta-carotene increases your risk of lung cancer. Is that true?
A. High doses of beta-carotene from supplements do raise the risk of lung cancer in some people, but beta-carotene from foods like carrots does not. So, eat as many carrots—and other vegetables and fruits—as you want. They are very healthy, packed with nutrients, and might help reduce your risk of some chronic diseases.
The link between lung cancer and beta-carotene supplements (a form of vitamin A) comes from a few large studies. These studies found that people who smoke, used to smoke, or who work with asbestos had a higher risk of lung cancer when they took dietary supplements containing 20 to 30 mg per day of beta-carotene for several years.
These doses are very high. Typical amounts of beta-carotene in most dietary supplements, such as multivitamins, are much lower and are not linked to an increased risk of lung cancer. For example, a supplement might contain 1 mg (written as 1,000 micrograms [mcg]) of vitamin A, with about 1/3 as beta-carotene, but check product labels.
Have more questions? See our fact sheet on vitamin A and carotenoids.
Q. Is it common to need vitamin B12 injections?
A. Vitamin B12 is found naturally in a wide variety of animal foods, including fish, meat, poultry, eggs, and milk. It’s also added to some fortified breakfast cereals and nutritional yeasts.
Most people in the United States get enough vitamin B12 from the foods they eat. Vitamin B12 deficiency is still common, though, affecting up to 15 percent of the population. This is mainly because some people—particularly older adults and those with certain health conditions such as pernicious anemia—have trouble absorbing vitamin B12 from food.
Although many of these people can absorb the synthetic vitamin B12 added to fortified foods and dietary supplements, some can’t. So, it’s possible to have a vitamin B12 deficiency even if you’re getting the recommended amount of vitamin B12 from your diet.
Vitamin B12 deficiency is usually treated with injections, so it goes directly into your body and doesn’t have to be absorbed like vitamin B12 taken orally.
Have more questions? See fact sheet on vitamin B12.
Q. My supplement has 500 mcg of vitamin B12, and the label says that it provides 20830% of the DV. Is that correct? It seems like too much.
A. Yes, the supplement is labeled correctly. The daily value (DV) for vitamin B12 is only 2.4 micrograms (mcg), so a 500-mcg supplement provides 20,830% of the DV. Multivitamin/mineral supplements frequently provide around 100% of the DV for many nutrients, but it is common to find supplements of vitamin B12 (and other B vitamins) that provide much higher doses. Even though most people don’t need such high amounts, vitamin B12 does not have an upper limit, so taking a lot isn’t likely to cause any problems.
Most people consume enough vitamin B12 from the foods they eat, but only animal foods naturally contain vitamin B12. Therefore, vegetarians—especially vegans who eat no animal products—need to get vitamin B12 from either fortified foods, such as many breakfast cereals and nutritional yeast products, or dietary supplements. In addition, some people—especially adults over age 50—have trouble absorbing the form of vitamin B12 that is naturally found in food. For these reasons, as much as 15% of the population might have a vitamin B12 deficiency. Vitamin B12 injections (which are administered by your health care provider) or vitamin B12 supplements can help correct a deficiency.
Have more questions? See fact sheet on vitamin B12.
Q. I know that dairy products like milk, yogurt, and cheese contain vitamin B12, but why isn’t it listed on the Nutrition Facts labels?
A. Food labels are not required to list vitamin B12 unless it has been added to the food. Therefore, you can’t rely on product labels to learn if a food naturally contains vitamin B12 and if so, how much.
For example, one cup of milk contains 1.3 mcg of vitamin B12. That’s a little over 50% of the Daily Value (DV). Six ounces of plain yogurt has 1.0 mcg and 1 ½ ounces of cheddar cheese has 0.5 mcg.
See vitamin B12 fact sheet lists other foods and the amounts of vitamin B12 they contain.
Q. Can vitamin C prevent colds or make them shorter?
A. This is a common question and one that many scientists have tried to answer. Overall, the research shows that for most people, taking vitamin C regularly does not reduce the chances of getting the common cold. Vitamin C supplements might slightly shorten the duration of a cold and lessen its severity. However, taking vitamin C after the onset of cold symptoms doesn’t appear to help.
Taking too much vitamin C can cause diarrhea, nausea, and stomach cramps. Most adults need between 75 and 90 milligrams (mg) of vitamin C per day and shouldn’t get more than 2,000 mg.
Have more questions? See fact sheet on vitamin C.
Q. Should I take a vitamin D supplement?
A. It depends. You need vitamin D for strong, healthy bones and to help prevent osteoporosis. Researchers are also studying vitamin D to see if it affects your risk of getting diseases such as diabetes and cancer, but they still don’t fully understand all of its effects in the body.
Most children and adults should get 15 micrograms (mcg) or 600 International Units (IU) a day, while those age 70 and older need 20 mcg or 800 IU.
Good sources of vitamin D include fatty fish, such as salmon and tuna, and fortified milk. Our bodies also make vitamin D when our skin is exposed to the sun. Knowing exactly how much vitamin D you’re getting can be difficult. Your health care provider can help you determine whether you might need a vitamin D supplement based on such factors as the foods you eat, your skin type, and the amount of sun you’re exposed to. Your health care provider can also test your vitamin D blood levels.
Have more questions? See fact sheet on vitamin D.
Q. What is the difference between vitamin D2 and vitamin D3?
A. Vitamin D comes in two forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms are well absorbed by the body and increase the amount of vitamin D in your blood. However, vitamin D3 might increase your blood levels of vitamin D slightly more and for longer than vitamin D2.
Have more questions? See fact sheet on vitamin D.
Q. I have been taking a vitamin D supplement that contains 400 IU, which is 100% of the DV. I just purchased another vitamin D supplement that also contains 400 IU, but its label says it provides only 50% of the DV. How can that be?
A. There is a simple explanation—the supplement you are currently using has the old Supplement Facts label, and the one you just purchased has the new label. For many years, the DV for vitamin D was 400 IU. Therefore, a vitamin D supplement containing 400 IU would provide 100% of the DV.
However, research shows that many adults need somewhat more vitamin D than previously thought. So, the FDA increased the DV for vitamin D and also changed the units.
The new DV is 20 mcg (micrograms), which is equal to 800 IU. Because the DV has changed, a 400 IU vitamin D supplement bearing the new Supplement Facts label provides only half, or 50%, of the DV.
On the new label, manufacturers must list the amount of vitamin D in mcg, but they can also list it in IU to make the transition a little less confusing for consumers.
Have more questions? See fact sheet on vitamin D.
Q. My cardiologist recommended a 100 IU supplement of natural vitamin E. I found a supplement that has 100 mg of vitamin E. is that the same as 100 IU?
A. No, 100 milligrams (mg) of vitamin E is not the same as 100 International Units (IU); the units make a difference.
The amount that your cardiologist recommended—100 IU of natural vitamin E—is equal to 67 mg of vitamin E. This is because 1 IU of natural vitamin E is equal to 0.67 mg of vitamin E.
As you noticed, vitamin E is labeled in mg on the new Supplement Facts label instead of IU. It now matches the units used for vitamin E’s recommended intake, which is 15 mg for most adults.
Have more questions: See fact sheet on vitamin E.
Q. My teenaged daughter drinks milk occasionally, but not every day. How much milk does she need to get enough calcium?
A. Teenagers should get 1,300 milligrams (mg) of calcium a day for good health. There are about 300 mg of calcium in 1 cup of milk, so your daughter would need to drink about 4 cups of milk to get the daily recommended amount.
But of course, this assumes that milk is your daughter’s only source of calcium. Your daughter will also get calcium from other foods and beverages, including cheese, yogurt, calcium-fortified cereals and juices, and some beans and vegetables, such as soybeans, spinach, and kale.
Nevertheless, many teenaged boys and girls do not get enough calcium. The same is true for many women after menopause and people who avoid dairy products. In these cases, a calcium supplement might help, but please talk with your health care provider for advice.
Have more questions? See fact sheet on calcium.
Q. I am a 60-year-old woman and have been taking calcium supplements for many years. Recently I’ve heard that they might increase the risk of heart disease. Is that true?
A. Many people, especially women, take calcium supplements. As you know, it is important to get enough calcium (and vitamin D) for good bone health. And although it is often best to get vitamins and minerals from foods and beverages, some supplements can help you get enough of certain nutrients.
Whether calcium affects the risk of cardiovascular disease is not clear. Some studies show that it might protect people from heart disease and stroke. But other studies have found that some people who consume high amounts of calcium, particularly from supplements, might have an increased risk of heart disease.
Much of your risk depends on your diet, lifestyle, current health, and medical and family history. Talk with your health care provider about calcium, bone health, and heart disease to figure out what is right for you.
Have more questions? See fact sheet on calcium.
Q. What is the difference between calcium carbonate, calcium citrate, and other forms of calcium supplements?
A. The main difference between various calcium supplements is the form of calcium they contain, and one isn’t necessarily better than another for you. The two most common forms are calcium carbonate and calcium citrate. Calcium carbonate is not well absorbed and needs food for slightly better absorption. Calcium citrate is absorbed well on an empty or a full stomach. In addition, people with low levels of stomach acid (which is more common in people aged 50 and older) absorb calcium citrate more easily than calcium carbonate.
One of the most important things to consider about calcium supplements, aside from the form of calcium, is how much to take at one time. The body absorbs calcium best in doses of 500 milligrams (mg) or less at a time. So, for example, if you take 1,000 mg of calcium from supplements per day, you might split the dose and take 500 mg at two separate times during the day.
Have more questions? See fact sheet on calcium.
Q. Some dietary supplements contain high doses of biotin and are promoted for hair, skin, and nail health. Do they work?
A. Biotin is a B vitamin found mainly in meat, eggs, fish, nuts, and some vegetables. A biotin deficiency can cause skin rashes, hair loss, and brittle nails—hence, the belief that taking extra biotin will produce healthier skin, thick hair, and strong nails. But it’s not clear if these claims hold up.
One of the most common misconceptions about vitamins and minerals is that if a nutrient deficiency causes a particular set of symptoms, then taking more of that nutrient will not only reverse those symptoms but will actually leave you better off. The reality is, if you are already getting enough, getting more doesn’t usually help.
Biotin helps metabolize the food we eat into the energy we need. The recommended amount of biotin for adults is 30 micrograms (mcg) per day, and you can get this much by eating a wide variety of nutritious foods. For example, a meal with 3 ounces of salmon, 3/4 cup of cooked sweet potato, 1/2 cup of cooked spinach, 1/4 cup of roasted almonds, and 1 cup of 2 percent milk provides about 11 mcg of biotin.
Some dietary supplements contain between 2,500 and 5,000 mcg of biotin, which are very high doses. In a few small scientific studies, some people with thin and brittle nails who took high doses of biotin had harder nails. And in a few cases, high doses of biotin improved a rare hair disorder in children and skin rash in infants. But the results of these studies are too preliminary to recommend biotin for any of these conditions.
Biotin doesn’t have an upper intake limit because there’s no evidence that it’s toxic, even at high doses. Most vitamins and minerals, however, do have upper limits, and getting too much can be unsafe. Some can also interact with medications or lab tests. Biotin, for example, can cause false results on some lab tests, including those that measure thyroid hormone levels. For these and other reasons, we always recommend talking with your health care provider about vitamins, minerals, and other dietary supplements to help you determine which, if any, may be of value.
Have more questions? See fact sheet on biotin.
Q. I know that the B vitamin folic acid helps prevent birth defects, so it’s important to take during pregnancy, but why are women supposed to take it before getting pregnant?
A. Yes, getting enough folic acid helps prevent birth defects, especially a kind called neural tube defects. These types of birth defects occur when the neural tube (where the brain and spinal cord form) doesn’t close properly in the fetus.
The neural tube closes very early in pregnancy—only 3 to 4 weeks after conception. This is right around the time most women realize they are pregnant, so waiting to take folic acid until you find out that you are pregnant might be too late.
If you could become pregnant, you should get 400 micrograms (mcg) of folic acid per day from dietary supplements and/or fortified foods (such as enriched breads, cereals, pastas, and other grain products). This is in addition to the amount you get naturally from foods and beverages. The recommended amount goes up to 600 mcg per day once a woman is pregnant because folic acid has many other important functions during the remaining months of pregnancy.
Have more questions about folic acid? See fact sheet on folate.
Q. I am taking a B-100 dietary supplement. It contains very high doses of vitamin B6, vitamin B12, and several other vitamins. Is it safe?
A. Many of the B vitamins—including vitamin B12, thiamin, and riboflavin—do not appear to be harmful at high doses. Therefore, scientists have not established safe upper limits for these nutrients. However, other B vitamins—including niacin and vitamin B6—do have upper limits and can cause problems if you get too much. This is particularly true for vitamin B6 which has an upper limit of 100 milligrams (mg) per day. Getting too much vitamin B6 can cause painful, unsightly skin patches, sensitivity to sunlight, nausea, and heartburn. If you take excessive amounts for a year or more, vitamin B6 can also cause nerve damage that can lead you to lose control of bodily movements. Unless your health care provider has recommended a high-dose B vitamin supplement, it’s safest to look for supplements that do not provide amounts at or above the upper limits.
Have more questions? See fact sheet on vitamin B6 along with our other vitamin and mineral fact sheets.
Q. Can vitamin B6 reduce the symptoms of premenstrual syndrome (PMS)?
A. Vitamin B6 may be helpful for PMS, but scientists aren’t sure. Some research shows that taking vitamin B6 supplements (about 80 milligrams [mg] per day) might reduce PMS symptoms including moodiness, irritability, forgetfulness, bloating, and anxiety. But more research is needed to confirm these findings. In addition, it’s important to know that taking too much vitamin B6 as a supplement—more than 100 mg per day for adults—can cause severe nerve damage and other health problems.
If you want to try vitamin B6 for PMS, talk with your health care provider first.
Have more questions? See fact sheet on vitamin B6 .
Q. My 17-year-old daughter has decided to follow a vegetarian diet. I’m worried that she’s not getting enough iron. Should she take an iron supplement?
A. Your daughter’s health care provider is the best person to help you determine whether she is getting enough iron from her diet or if she might benefit from a supplement.
The daily recommended amount of iron is 15 milligrams (mg) for a teenage girl. Although meat, poultry, and seafood are the richest sources of iron, many plant foods—including beans, nuts, and vegetables—also contain iron. Iron is also added to many fortified breads, cereals, and other grain products.
Vegetarians can get enough iron from foods. However, our bodies don’t absorb the form of iron in plant foods and fortified foods as well as the form of iron found in animal products. For this reason, vegetarians need to consume almost twice as much iron as non-vegetarians.
See fact sheet on iron provides more details, including the recommended daily amounts of iron for various age groups.
Q. Is magnesium helpful for muscle cramps?
A. As with all vitamins and minerals, it’s important to get enough magnesium for good health. Muscle cramps are one of the signs of a magnesium deficiency, so if you are not getting enough magnesium, getting more might help. But in most cases, muscle cramps are caused by other things. We recommend talking with your health care provider to determine if muscle cramps, or any other symptoms you have, might be a sign of a magnesium deficiency or something else.
Have more questions? See fact sheet on magnesium.
Q. Can magnesium help prevent migraine headaches?
A. Research shows that people who get migraine headaches tend to have lower levels of magnesium than those who don’t. This suggests—but doesn’t prove—that consuming more magnesium might decrease the chance of getting migraines.
According to a few small studies, taking magnesium supplements (about 300 milligrams [mg] twice a day) alone or in combination with medication might help prevent migraines. But this should be done only under the guidance of a health care provider because taking too much magnesium as a supplement can cause problems. If you want to try magnesium for migraine headaches, we recommend talking with your health care provider.
Have more questions? See fact sheet on magnesium.
Q. I know bananas contain potassium. Can I get enough potassium by eating a banana every day?
A. Bananas do have a lot of potassium compared to many other foods but eating one banana a day won’t meet your potassium needs alone. A medium banana has about 420 milligrams (mg) of potassium, so you would have to eat at least 6 to 8 bananas to meet the 2,600 to 3,400 mg of potassium that adults should get each day. Obviously, that’s not the best approach. Instead, eat a nutritious variety of foods that contain potassium to ensure you get enough of this important nutrient.
Have more questions? See fact sheet on potassium.
Q. I can’t find a potassium supplement that provides very much potassium. Why?
A. Most dietary supplements contain less than 100 milligrams (mg) of potassium, which is only about 3 to 4% of the daily recommended amount for adults. This is partly because of reports that some potassium-containing medications may damage the gastrointestinal tract. Although the U.S. Food and Drug Administration (FDA) does not limit the amount of potassium in dietary supplements, they do require warning labels on some medications that contain 100 mg of potassium or more.
Because of the small amounts of potassium in dietary supplements, you can’t rely on them to help meet your potassium needs. This underscores the importance of getting potassium by consuming a nutritious variety of foods.
Have more questions? See fact sheet on potassium.
Q. Can potassium help lower my blood pressure?
A. Yes, it might. People with low intakes of potassium have an increased risk of high blood pressure, especially if you consume a lot of sodium (salt). Therefore, increasing your potassium intake, along with decreasing sodium intake, might help lower your blood pressure and reduce your risk of stroke. One way to do this is to follow an eating plan called DASH (Dietary Approaches to Stop Hypertension), which emphasizes potassium from fruits, vegetables, and low-fat dairy products. Also, using potassium-containing salt substitutes in place of regular salt helps lower blood pressure. But it’s not clear whether this is because of the increased potassium, reduced sodium, or both.
Have more questions? See fact sheet on potassium.
Q. Does all salt contain iodine? What about sea salt?
A. Only salt that is labeled as “iodized” contains iodine. Specialty salts such as sea salt, kosher salt, Himalayan salt, and fleur de sel usually contain little or no iodine. For comparison, ¼ teaspoon of iodized salt contains about 75 micrograms (mcg) of iodine, whereas the same amount of non-iodized sea salt contains less than 1 mcg.
Check product labels to see if the salt is iodized or provides iodine (usually listed as “iodide”). But keep in mind that the iodine in salt decreases over time, especially if the salt is stored in a warm, humid location. Because of this, keep your iodized salt in a cool, dry location and purchase a new container occasionally, like at the start of each new year.
Processed foods such as canned soups are rarely made with iodized salt, so even if these foods contain salt, the salt likely doesn’t supply any iodine. If the manufacturer does use iodized salt, the salt will be listed as iodized in the ingredient list on the food label.
For more information about iodine, including the health problems that can occur if you get too little or too much, see iodine fact sheet and talk with your health care provider for specific advice.
Q. I am pregnant and follow a vegan diet. Because iodine is present mainly in animal products, how can I get enough?
A. Women who are pregnant need 220 micrograms (mcg) of iodine a day. Most fruits, vegetables, and other plant foods contain very little iodine (usually less than about 7 mcg per serving). So, if you follow a vegan diet or eat few or no dairy products, seaweed, seafood, or eggs, you might not get enough iodine. Also, if you don’t use iodized salt, your iodine intake might be low.
Getting too little iodine could affect your baby’s development. Because of this, the American Thyroid Association recommends a daily supplement containing 150 mcg of iodine for pregnant and breastfeeding women. Many standard multivitamin/mineral supplements contain iodine, but only about half of prenatal supplements contain iodine. Talk with your health care provider to determine what’s right for you.
See iodine fact sheet which has more information about the importance of iodine during pregnancy and infancy.
Q. I am pregnant and my friend told me to make sure I get enough iodine. I’ve never thought about iodine before. How can I make sure I’m getting enough, but not too much?
A. Some pregnant women in the United States might not get quite enough iodine. Iodine has many important roles in the body, including proper bone and brain development. Talk with your health care provider about iodine as part of your prenatal care.
Iodine is found naturally in some foods, but amounts vary. Good sources include seaweed, fish and other seafood, and eggs. Iodized salt is another good source of iodine and is readily available in grocery stores. But processed foods, like canned soups, almost never contain iodized salt.
The American Thyroid Association recommends that pregnant and breastfeeding women take dietary supplements containing iodine (150 micrograms [mcg] per day). Many standard multivitamin/mineral supplements contain iodine, but only about half of prenatal supplements contain iodine.
Keep in mind that it is possible to get too much iodine, and this can cause problems too. The safe upper limit for adults is 1,100 mcg per day, but most people are unlikely to go above this amount. For example, a 3-ounce serving of baked cod has about 160 mcg of iodine, and ¼ teaspoon of iodized salt contains about 75 mcg of iodine.
Have more questions? See iodine fact sheet.
Q. I have macular degeneration, and my ophthalmologist suggested taking a dietary supplement to preserve my vision as long as possible. Is there research to back this up, and if so, which supplement should I buy?
A. Many dietary supplements promoted for vision or eye health are based on formulations tested in the Age-Related Eye Disease Studies (AREDS), a series of large clinical trials sponsored by the National Institutes of Health. These studies found that among people with age-related macular degeneration (AMD) who were at high risk of developing advanced AMD, supplements containing vitamin E, vitamin C, zinc, copper, and either beta-carotene or lutein plus zeaxanthin helped slow down the rate of vision loss. Adding the omega-3 fatty acids EPA and DHA to the supplements didn’t help, but it didn’t do any harm either.
The types and amounts of ingredients in commercially available eye-health supplements vary. We recommend asking your health care provider to make a recommendation. You can also see the specific formulations that were tested in the AREDS studies, along with the study results, on the National Eye Institute website.
Q. I suffer from migraine headaches, and I’ve heard that riboflavin might help. Is riboflavin safe to take for migraines?
A. Riboflavin is a B vitamin that is sometimes called vitamin B2. A number of foods, including eggs, organ meats (such as kidneys and liver), lean meats, low-fat milk, and green vegetables, contain riboflavin. It’s also added to enriched cereals, bread, and grain products.
Some studies show that riboflavin supplements might help prevent migraine headaches, but other studies do not. Even though not all studies agree, several professional societies recommend trying riboflavin because it might be effective and has few side effects. The Canadian Headache Society, for example, recommends 400 milligrams (mg)/day of riboflavin, under the guidance of a health care provider, for preventing migraines. This is a very large daily dose, so we advise talking with your health care provider about riboflavin and migraines to find out what’s best for you.
Have more questions? See fact sheet on riboflavin.
Q. Are Brazil nuts a good way to get enough selenium?
A. Yes, Brazil nuts are very high in selenium. But they contain so much selenium that it can be unsafe to eat too many of them.
Like other vitamins and minerals, selenium has a recommended intake and a safe upper limit. Adults should get at least 55 to 70 micrograms (mcg) of selenium, but not more than 400 mcg a day.
One Brazil nut has about 70 to 90 mcg of selenium. So eating one or two Brazil nuts a day is a great way to get enough selenium. But if you eat more than a small handful of Brazil nuts, you could easily go over the upper limit.
Getting too much selenium on a regular basis can cause several problems including an upset stomach, garlic breath odor, hair loss, white blotchy nails, and mild nerve damage.
Have more questions? See fact sheet on selenium.
Q. Can zinc make your hair grow?
A. Like all vitamins and minerals, it’s important to get enough zinc for good health. In most cases, hair loss is hereditary and is not related to the amount of zinc you consume. But it is true that a zinc deficiency can cause hair loss in otherwise healthy individuals. If you have a zinc deficiency, increasing your zinc intake to correct the deficiency should help. But this doesn’t mean that taking extra zinc will make your hair thicker or longer.
Most people in the United States get enough zinc from the foods they eat, about 8 to 11 milligrams (mg) per day for adults. You can get the recommended amount by eating a variety of foods, including red meat, poultry, oysters and other seafood, beans, nuts, whole grains, and dairy products.
Getting too much zinc—more than 40-50 mg per day for adults—can cause problems such as nausea, vomiting, and low copper levels. So, the bottom line is, make sure you’re getting enough zinc but not too much.
Have more questions? See fact sheet on zinc.
Q. Does zinc help prevent or treat COVID-19?
A. Getting enough zinc is important for a healthy immune system, but taking zinc supplements hasn’t been shown to lower your risk of getting COVID-19 or help you recover quicker. For example, in one study, people who took zinc supplements regularly did not have a lower risk of getting COVID-19 than those who did not take zinc supplements. In another study, people with COVID-19 were split into four groups and took one of the following for 10 days: 50 mg zinc, 8,000 mg vitamin C, both supplements, or neither one. Zinc did not shorten the duration of symptoms.
Have more questions? See Dietary Supplements in the Time of COVID-19 fact sheet.
Q. Is zinc helpful for the common cold or other illnesses?
A. Zinc might help with some illnesses in certain people. For example, lozenges that contain zinc might speed recovery from the common cold if you start taking them shortly after coming down with cold symptoms. In addition, zinc supplements help reduce the duration of diarrhea in children in developing countries. These children are often zinc deficient or otherwise malnourished. It’s not clear whether zinc supplements are helpful for diarrhea in children who get enough zinc, such as most children in the United States.
Have more questions? See fact sheet on zinc.
Q. I recently heard that people can get too much zinc from using denture creams. Is that really possible?
A. Yes. Zinc is present in some denture cream adhesives. Using large amounts of zinc-containing denture creams (well beyond recommended levels) could lead to excessive zinc intake. Too much zinc can cause copper deficiency and nervous system problems, such as numbness and weakness in the arms and legs.
The safe upper limit for zinc is 40 mg per day. Many denture creams have been reformulated so that they don’t contain zinc, but check product labels to be sure.
Have more questions? See fact sheet on zinc.
Q. What are the upper limits for vitamins and minerals?
A. Our bodies need vitamins and minerals for many things, like breaking down the food we eat, making bones and DNA, helping muscles contract, and maintaining immunity. But there’s no reason to get more than you need, and some nutrients can be dangerous in large amounts.
Each vitamin and mineral has a recommended amount, which is what you should get each day for good health. Most of them also have what is called a “tolerable upper intake level” or UL. Getting more than the UL can cause health problems. Other vitamins and minerals appear to be safe at any dose, while a few have a UL only under certain circumstances.
Which vitamins and minerals fall into which category? Here’s the breakdown:
Stay under the UL each day for these nutrients to avoid health problems unless your health care provider recommends more. For example, very high doses of vitamin B6 can cause severe nerve damage and too much iron can be fatal. The ULs for these nutrients include what you get from food, beverages, fortified foods (including many breakfast cereals), and dietary supplements. But it’s unlikely you’ll go above the UL from food and beverages alone.
These vitamins and minerals, as found naturally in food and beverages, won’t cause any health problems. But they can if you get amounts above the UL from supplements or fortified foods.
Vitamin A exists in two main forms: preformed vitamin A—such as retinol and retinyl palmitate—in animal products (including meat, poultry, fish, and dairy products); and beta-carotene (in fruits, vegetables, and other plant foods). Dietary supplements can contain both forms.
Only preformed vitamin A has a UL because high amounts can cause health problems, such as birth defects during pregnancy and liver damage. Beta-carotene has no UL because high amounts don’t cause these problems.
These nutrients have no identified safety concerns, even at high doses. But there’s no reason to get more than recommended amounts unless your health care provider recommends it.
Have more questions? See fact sheets on vitamins and minerals for details about the recommended amounts and ULs.
Q. Are dietary supplements regulated?
A. Yes. The U.S. Food and Drug Administration (FDA) regulates dietary supplements but does so under a different set of regulations than those covering “conventional” foods and medicines (prescription and over-the-counter). Medicines must be approved for safety and effectiveness by FDA before they can be sold or marketed. Supplements do not require this approval. Under the Dietary Supplement Health and Education Act of 1994, the dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. FDA is responsible for taking action against any unsafe dietary supplement product after it reaches the market.
Supplement companies are expected to have evidence that their product claims are truthful and not misleading. However, FDA does not determine whether dietary supplements are effective before they are marketed. FDA’s post-marketing responsibilities include monitoring safety, e.g. dietary supplement adverse event reporting, and product information, such as labeling, claims, package inserts, and accompanying literature.
For more details, please see Dietary Supplements: What You Need to Know.
For more information on dietary supplement regulations, please contact the FDA Office of Dietary Supplement Programs by email at [email protected].
The Federal Trade Commission (FTC) regulates advertising of dietary supplements in national or regional newspapers and magazines; in radio and TV commercials, including infomercials; through direct mail to consumers; or on the internet. The FTC requires that all information about supplements be truthful and not misleading.
For more information on dietary supplement advertising, please contact the FTC via their website.
