DEAR DOCTOR K:

Many herbs, vitamins and supplements claim to boost energy. Do any of them actually work?

DEAR READER:

Unfortunately, there is not much scientific evidence to support the claims. Here is my best current assessment of the published evidence:

-- Ginkgo biloba. It may improve alertness and calmness in healthy people. If you take a daily aspirin, or any other blood thinners, I'd avoid ginkgo. It may increase a bleeding tendency.

-- Ginseng. This is a relatively safe herb, but there's not much evidence that it reduces fatigue.

-- Guarana. This herb induces a feeling of energy because it's a natural source of caffeine. But consuming a lot of guarana could ultimately lower your energy by interfering with sleep.

-- Chromium picolinate. This mineral is widely marketed to build muscle, burn fat, and increase energy and athletic performance. Research has not supported these claims.

-- Vitamin B12. Some people take vitamin B12 as a way to get a quick energy burst. If you have a B12 deficiency, which is easy to determine with a simple blood test, treatment definitely can improve your energy.

-- DHEA. This naturally occurring hormone is said to boost energy, among other things. But DHEA has no proven benefits and some potentially serious health risks. It is particularly wise to avoid it if you are pregnant or breast-feeding, have liver disease, polycystic ovarian syndrome, high blood levels of cholesterol or depression.

-- Coenzyme Q10. This enzyme may improve exercise capacity in people with heart disease, and one small study found that people with chronic fatigue syndrome might benefit from this supplement. However, its value as a general energy booster is unproven.

-- Creatine. Creatine is produced by the body and is largely found in muscle. There is evidence that it can build muscle mass and improve athletic performance requiring short bursts of muscle activity, particularly in teenagers and young adults (but not in older adults). However, it has not been proven to reduce fatigue. If you take creatine, stick to the recommended dose (2 to 3 grams per day).

-- Ephedra. The FDA banned ephedra because of major safety concerns, but it remains available for sale on the Internet. There is no safe dose of ephedra. Avoid it.

We have more information on ways to increase your energy in our Special Health Report, "Boosting Your Energy." (Learn more about this report at AskDoctorK.com, or call 877-649-9457 toll-free to order it.)

Having said all this, the studies I refer to above determine whether the average person gets a benefit from a treatment. But it is entirely possible that some people really do get a benefit even if the average person does not. So if a supplement is not harmful and seems to be helping, I don't discourage my patients from taking it.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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