Dietary Supplements

What are dietary supplements?

Dietary supplements are products that you may take by mouth to add nutrients to your diet. You can buy them in the form of pills, tablets, capsules, liquids, or powders. Supplements include:

  • Vitamins and minerals
  • Amino acids
  • Herbs
  • Probiotics
  • Enzymes

The US Food and Drug Administration (FDA) does not regulate or approve supplements. The FDA does have guidelines about what health claims can be made. Products cannot claim to treat or cure diseases, to keep you from getting sick, or to help you live longer. Be careful when you choose supplements. Supplements can cause problems with other medicines that you take. Always talk with your healthcare provider about what you are taking or plan to take.

Vitamins and minerals

Vitamins and minerals are chemicals that your body cannot make on its own, and that are needed to stay healthy. A healthy diet is the best way to get these nutrients. However, you may not eat enough different foods to get all of the vitamins and minerals that you need. Examples of people who may need to take supplements include:

  • Women who may get pregnant should take a folic acid supplement.
  • Adults and children who do not get out in the sun may need a vitamin D supplement.
  • Adults age 50 and older may need to eat foods fortified with vitamin B12 or take a supplement that contains vitamin B12.
  • People who have osteoporosis may need to take calcium and vitamin D supplements.
  • People with age-related macular degeneration may need to take a specific formula of vitamins and minerals to reduce the risk of vision loss.
  • People who cannot absorb certain nutrients may need to take specific supplements.

You may want to add a daily multivitamin and mineral supplement to your diet, but supplements are not a substitute for a healthy diet. If you decide to take vitamins and minerals, follow these guidelines:

  • Check with your healthcare provider, pharmacist, or dietitian first, especially if you take prescription medicine or are being treated for a health problem.
  • Choose a supplement that gives no more than 100% of the daily value for the vitamins and minerals. This helps you avoid taking too much. Don’t take very large doses. Taking too much of some supplements, especially as you get older, can be poisonous.
  • Store brands or generic brands can be as effective as brand names. Many types of formulas are available. Ask your pharmacist, dietitian, or healthcare provider what is best for you.
  • Look for stamps or seals of approval from USP (US Pharmacopeia),, and NSF (National Science Foundation.) These seals tell you that the product has passed quality tests. This means that it contains the ingredients listed, and that it is not contaminated. The stamp does not promise that the product is safe or effective.

Amino acids

Amino acids are the building blocks that form proteins. Some amino acids are made by the body, and you get others from the food you eat. Most people get more than enough amino acids from their diet. However, some amino acids are sold as supplements, such as lysine, tryptophan, arginine, carnitine, and homocysteine. Do not take amino acids unless your healthcare provider tells you to do so. They can have dangerous effects. For example, arginine may increase the risk of death after a heart attack.

Herbal supplements

Herbal supplements are made from plants. Ginkgo biloba, ginseng, echinacea, and black cohosh are examples of herbal supplements. People think of herbal supplements as “natural,” but:

  • “Natural” does not always mean safe. Some herbs can cause serious side effects such as high blood pressure, diarrhea, heart attack, or stroke.
  • Because they have an effect on your body, herbs can interfere with medicines you may already be taking. For example, St. John’s wort can make blood-thinner medicines less effective. Black cohosh may interfere with treatment for breast or ovarian cancer.

If you are thinking about taking an herbal supplement, ask your healthcare provider, pharmacist, or dietitian about it.


Probiotic is a term used to describe helpful bacteria that help digestion. They can also help keep you from having too many harmful bacteria in your body.

If you take antibiotics, the medicine may kill the good bacteria. You may then have too many bad bacteria. This can cause diarrhea or a vaginal yeast infection. Probiotic supplements contain high doses of good bacteria. They can be used to balance the bacteria in your system.

Probiotics may also help:

  • Treat irritable bowel syndrome.
  • Prevent inflammation after some kinds of intestinal surgery.
  • Prevent a skin problem called eczema in children.

Probiotic supplements can be bought without a prescription. Probiotics can also be found in foods such as yogurt, miso, and some juices and soy drinks.

Probiotics do not help everyone who has problems with an overgrowth of harmful bacteria. Tell your healthcare provider if you plan to try a probiotic supplement.


Enzymes are proteins made by the body. They help your body in many important ways. For example, digestive enzymes help your body break down and use the food you eat. You may need digestive enzymes if your body cannot make enough of these enzymes. Lactase is an example of a digestive enzyme. Lactase helps if you have trouble digesting milk products.

Most people do not need to take digestive enzymes. If you have digestive problems, ask your healthcare provider if a supplement might help you.

What’s best for me?

Supplements are not inspected or regulated the way that prescription medicines are. If you are thinking about using supplements, remember:

  • Dietary supplements are not standardized. They may have different strengths and effects. Some may contain things that are harmful to you. Be careful about which products you use.
  • Do not self-diagnose any health condition. Talk to your healthcare provider, pharmacist, or dietitian before you buy something to try to treat yourself. Just because something worked for someone else does not mean that it will work for you. Use only the supplement your provider or dietitian tells you to take.
  • Don’t buy combinations that have ingredients you do not want or need.
  • If your provider does not suggest a dietary supplement, but you decide to use one anyway, tell your provider. Then he or she can keep an eye on your health and adjust your other medicines if needed.

For more information contact:

Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2014-02-13
Last reviewed: 2013-05-02
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

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