What You Need to Know About Dietary Supplements

Safety First

The most important thing to remember when thinking about supplements is that just because something is natural does not mean it is safe or can be taken without risk. Supplements may interact with prescription medications and cause serious problems. They can have side effects. They may also cause problems if they are taken in large amounts or mixed with other over-the-counter products.

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Do not use any supplement before talking about it with your doctor. Some people should use extra caution or completely avoid taking supplements, including:

  • women who are pregnant or nursing.
  • women taking birth control pills.
  • people with kidney, liver, or heart problems, or certain other medical conditions.
  • people with HIV.
  • people taking prescription or over-the-counter medications.
  • children.
  • people who have had organ transplants.

Supplements are regulated by the Food and Drug Administration as food products rather than drugs. Therefore, they do not have to meet the same standards as prescription and over-the-counter medications for proof of safety, effectiveness, or dosage.

Published studies of supplements have found that some herbal supplements may contain different amounts of the active ingredients than their labels state. They may also contain harmful additives or contamination. Supplement labels might refer to the product's quality being "standardized," "certified," or "verified." There is no legal definition for these terms, so they may not guarantee quality.

Omega-3 Fatty Acids

Omega-3 fatty acids, which occur naturally throughout the body, are currently being studied to determine their effectiveness in treating depression and bipolar disorder. These oils, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in shellfish, sardines, albacore tuna, salmon, canola oil, soybeans, flaxseed, walnuts, and wheat germ. They are also available in pill form. Omega-3 fatty acids have been shown to improve heart health, immune function and a variety of other conditions in some studies. In some clinical trials of people with depression or bipolar disorder, many people improved on high doses of omega-3 oils. Mild stomach side effects were reported by people taking omega-3 fatty acids.

Herbal Supplements

Herbal supplements are made from plants. Their manufacturers claim that they treat many illnesses, including depression. However, not much research has been done to confirm their effectiveness. Two herbal supplements generally used for depression are St. John's wort and SAM-e.

St. John's Wort

One of the most widely recognized herbal supplements for depression is St. John's wort (Hypericum perforatum). This plant and its flowers contain many chemicals, some of which are believed to be helpful. It is not yet known how St. John's wort works in the body. One theory is that it may prevent nerve cells in the brain from reabsorbing serotonin, thereby reducing depression. St. John's wort is prescribed in some European countries for depression, although it is not available by prescription in the U.S. Some, but not all studies have shown it to be effective in treating mild to moderate cases of depression. In studies involving people with severe depression, St. John's wort has had little or no effect. Common side effects of St. John's wort are dry mouth, dizziness, diarrhea, nausea, fatigue, and increased sensitivity to sunlight. It can also interact with other medications, including birth control pills, and affect the way the body gets rid of or metabolizes them.


S-Adenosyl-L-Methionine (SAM-e) was introduced in the United States in 1999, but has been widely used in some European countries for the treatment of arthritis and depression. SAM-e is a naturally occurring and essential substance in the human body. It is most concentrated in the liver and brain. It plays an important part in regulating serotonin and dopamine in the brain, two chemicals which influence mood. Some studies examining the effectiveness of SAM-e for the treatment of depression have found it to be more effective than placebo (sugar pills) in relieving depressive symptoms. However, compared with prescription medications commonly used to treat depression, SAM-e showed no better results. Another study involved patients with major depression who took SAM-e in addition to their prescribed antidepressants. Half of these patients showed some improvement and nearly half went into remission, no longer experiencing any symptoms. Common side effects associated with SAM-e include nausea and constipation. As with any treatment, it's important to discuss it in detail with your doctor and take the supplements under his or her supervision.

For More Information

National Institutes of Health, Office of Dietary Supplements
(301) 435-2920, http://www.ods.od.nih.gov/

National Center for Complimentary and Alternative Medicine

National Institute of Mental Health

National Library of Medicine

Alternative Medicine Foundation

HerbMed Database (Alternative Medicine Foundation)