March 12, 2010

Dear Mayo Clinic:

What are the dangers of taking over-the-counter supplements? I am on blood pressure medication and have heard that there are some supplements that may interfere.

Answer:

You 've heard correctly. Some supplements should be avoided when you are dealing with high blood pressure. Yet, preliminary evidence shows that a couple of supplements may be beneficial in your situation.

While supplements may be labeled "natural" and don 't require a prescription, they can affect the body in many ways. Supplements can interact with medications, change the body 's metabolism and cause side effects. Baseline advice for any supplements is to talk with your health care provider before you take them — no matter how harmless they may seem.

With high blood pressure, supplements on your caution list should include:

• St. John 's wort: Used to treat depression, St. John 's wort speeds up the metabolism of a number of medications. The blood pressure medication you take could be metabolized so quickly that it loses its effectiveness. The result could be an increase in blood pressure.
• Echinacea: Although echinacea is considered helpful for reducing cold and flu symptoms, some evidence indicates that it also changes how medications are metabolized.
• Ephedra: This supplement, used in weight-loss products, is banned in the United States because of safety concerns. Ephedra is linked to high blood pressure, heart attack, stroke and other serious health problems.
• Bitter orange: This supplement fills the niche vacated by ephedra in some weight-loss products. But that doesn 't necessarily mean it 's safer. Bitter orange can increase heart rate and blood pressure and has been linked to strokes and heart attacks.
• Yohimbine: In the past, yohimbine has been touted as an aid for erectile dysfunction. Its popularity seems to have declined, perhaps due to many side effects, including an increase in blood pressure.
• Ginseng: Preliminary evidence suggests that ginseng may lower blood sugar, decrease fatigue or boost the immune system. It also may raise or lower blood pressure. Ginseng is best avoided by patients with high or low blood pressure concerns.

Two supplements that have shown some benefit in your circumstance are fish oil and garlic.

Research has confirmed that routinely eating fatty fish, such as salmon, tuna and trout, can reduce the risk of heart disease and death. The heart benefits seem strongest when eating fatty fish twice a week. For those who don 't like or can 't eat fish, a fish oil supplement is an option. Some studies have shown that taking a fish oil supplement (4 grams daily) modestly reduces blood pressure in patients with mild hypertension. The evidence isn 't strong enough, however, for an all-out endorsement of fish oil as a means to lower blood pressure.

Garlic also is well known for its potential benefits to heart health, especially lowering high levels of lipids in the blood. And, some evidence indicates that garlic may relax smooth muscles and dilate blood vessels. Studies have shown that taking a garlic extract (200 to 400 milligrams three times daily for one month) can lower blood pressure modestly. This research is preliminary and is not enough to support taking garlic solely to lower blood pressure.

Supplements are never the whole answer to treat a medical condition. In addition to medication, I hope you and your doctor have discussed the benefits from a healthy diet, exercise and stress management. I always add one more to that list: Find ways to add meaning to your life — through work, relationships, volunteering or other activities. These four approaches are the basis for good health in general, no matter what condition you have.

When you hear about an intriguing supplement, do your homework. With the Internet, it 's not difficult to track down the research study that might be generating news. Check out the size of the study, whether the supplement was compared to a placebo, and details on the results. With that information in hand, talk with your doctor about how the supplement could affect your health.

— Brent Bauer, M.D., Internal Medicine, Mayo Clinic, Rochester, Minn.

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