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Dietary Supplements|Herbal Medicine|nutrition|vitamins

Dietary Supplements: What You Need to Know

Last Updated February 2024 | This article was created by editorial staff and reviewed by Beth Oller, MD

Dietary supplements are any substances you take to improve your health or wellness. This includes vitamins, minerals, and herbs. The most common form is a pill, or capsule. You also can get them in powders, drinks, and foods. These supplements aren’t meant to cure diseases or health conditions. An exception is if the U.S. Food and Drug Administration (FDA) has approved it for a health claim.

Path to improved health

Vitamins and minerals are known as micronutrients. They help nourish your body and keep you healthy. You can get them by eating a variety of foods in your daily diet. This ensures that your body can absorb them properly.

You should try to eat a variety of healthy foods, such as fruits, vegetables, lean meats, and fish. If you don’t, you may not get all the micronutrients your body needs. Taking a multivitamin can help. There is no proof that they help reduce your risk of cancer or heart disease.

People who may benefit from multivitamins include:

  • Women who are pregnant or trying to get pregnant.
  • Women who are breastfeeding.
  • Women who have heavy menstrual periods.
  • Women who have gone through menopause.
  • People who don’t eat animal products. This includes vegetarians and vegans.
  • People who have had gastric bypass surgery for weight loss.
  • People who have diseases of the stomach, liver, pancreas, or gall bladder.
  • People who have digestive health conditions. This includes gastrointestinal disease, lactose intolerance, or food allergies.

According to the U.S. Department of Agriculture (USDA), adult Americans may not get enough of the following micronutrients.

Nutrient Recommended Daily Amount (RDA)
Calcium 1,000 milligrams (mg) for men and women between 31-50 years
1,200 mg for women over 50 years old
1,000 mg for men between 51-70 years
1,200 mg for men older than 70 years
Fiber 25 grams (g) for women
38 g for men
Folic acid/Folate 400 micrograms (mcg)
Iron 8 mg for men
18 mg for women 19-50 years
8 mg for women older than 51 years
Magnesium 320 mg for women older than 50 years
420 mg for men older than 50 years
Potassium 4,700 mg for men and women older than 50 years
Vitamin A 2,310 international units (IU) for women
3,000 IU for men
Vitamin B12 2.4 mcg
Vitamin C 75 mg for women
90 mg for men
Vitamin D 600 IU
800 IU for men and women over 70 years
Vitamin E 15 mg

Hundreds of other supplements are available. They promise to treat a range of symptoms. However, evidence to support these claims often is missing. Some of the most popular herbs include:

  • Chondroitin sulfate
  • Coenzyme Q10 (CoQ10)
  • Digestive enzymes
  • Echinacea
  • Garlic
  • Gingko biloba
  • Ginseng
  • Glucosamine
  • Kava
  • Melatonin
  • Phytoestrogens, such as black cohosh, dong quai, and soy
  • Probiotics
  • Saw palmetto
  • John’s wort

Talk to your doctor before you begin taking a dietary supplement. They can tell you the benefits and risks of each supplement. Make sure they know about anything you already take. This includes all medicines, both prescription and over-the-counter (OTC). That’s because some medicines and supplements can react badly. Read the ingredient list on supplements to make sure you know what else is in them. Don’t take more than the recommended dosage on the label unless your doctor approves it. Just because a supplement is advertised as “natural” doesn’t mean it’s safe.

Things to consider

Talk to your doctor if you don’t think you’re getting enough vitamins and minerals in your diet. They can help you decide which micronutrients you need. Your doctor also can recommend a dietary supplement. This will depend on your overall health and lifestyle.

Supplements can cause problems with cancer treatments or surgery. Your doctor will know if they interact with any health conditions you have. For example, foods rich in vitamin E and beta-carotene are healthy. However, the U.S. Preventive Services Task Force (USPSTF) and the American Academy of Family Physicians (AAFP) recommend against taking vitamin E or beta-carotene for the prevention of cardiovascular disease and cancer. People who smoke or are at risk for lung cancer also should avoid beta-carotene. It can increase their risk of lung cancer.

It’s important to note that pharmaceutical companies obtain FDA approval and follow the agency’s regulations. Makers of supplements are not required to do this. Some makers of dietary supplements follow the U.S. Pharmacopeial (USP) Convention quality standards. This means they volunteer to have their products tested. An outside company will check them for quality and purity before they’re sold. These supplements display additional credentials on their labels. Look for them to say “USP Verified” or “ Approved Quality.”

Dietary supplements generally are safe if they aren’t used in excessive amounts. This is especially true for the fat-soluble vitamins A and E. Check the recommended daily allowance (RDA) on the label. Taking too much can cause unwanted or harmful side effects.

However, some herbal supplements may not be safe. They could contain unlisted ingredients that make you sick. Drugs that aren’t listed on the label can include steroids or estrogens. Products may even contain toxic, or poisonous, substances. Examples include arsenic, mercury, lead, and pesticides. Supplements must be recalled if they are found to contain toxic ingredients.

Questions for your doctor

  • Are dietary supplements safe?
  • Are “natural” dietary supplements safer?
  • How do I know if I need a dietary supplement?
  • What dietary supplements might be beneficial for me?
  • How do I know what dosage I should take?
  • How often should I take a dietary supplement?
  • Is a vitamin considered a dietary supplement?
  • Can dietary supplements interact with food or medicines I’m taking?
  • Can dietary supplements cause side effects?
  • Can the dietary supplements I take interfere with lab results?
  • Is there anyone who should avoid taking dietary supplements?
  • There are so many dietary supplements available at the store. How do I pick the right one for me?
  • Can I take dietary supplements if I’m pregnant or nursing?
  • What kinds of supplements are safe for children to take?


National Institutes of Health, MedlinePlus: Dietary Supplements

National Institutes of Health, MedlinePlus: Dietary Supplements

U.S. Food & Drug Administration: FDA 101: Dietary Supplements

U.S. Food & Drug Administration: Facts About Dietary Supplements

U.S. Pharmacopeial (USP) Convention: How to Choose a Quality Supplement

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