(FORTUNE Magazine) – Not long ago, a patient who asked his physician about acupuncture would have probably gotten a dirty look. Today some medical doctors have incorporated acupuncture into their practices, and studies suggest it can be useful for certain conditions, with surgical pain and nausea from anesthesia topping the list.

Complementary, alternative, integrative. They're all terms used to describe basically the same thing--types of healing that fall outside the bounds of conventional (allopathic) medicine. But complementary and alternative medicines (CAM) aren't really all that alternative. Over 40% of Americans now use some form of CAM. There are more patient visits each year to alternative practitioners than to conventional medical ones.

Part of CAM's popularity stems from the fact that it's mystical; it's seen as possessing powers derived from our own belief systems, our body's innate ability to heal itself, or life energy known--according to traditional Chinese medicine--as Qi. It's also believed to be "natural," implying it's safe, which isn't necessarily true (mushrooms are natural, but poisonous ones will do you in).

Most people who use CAM are not dissatisfied with their conventional medical care, but see it as an addition to their regular care. Many are in poor health and report better relief of symptoms with CAM. People with back problems, anxiety, or chronic pain are likely to use CAM therapies. Others decide to give it a try because there is no safe and effective conventional therapy for their medical condition.

Therapies vary widely. Naturopathy, Ayurvedic medicine, and homeopathy claim to be medically based, but the rationales behind them cannot easily be explained by mainstream medicine. Example: Homeopathy insists that the more diluted the remedy, the greater the potency. Very small amounts of different antidotes are given to treat serious conditions--just the opposite of conventional medicine, which holds that larger doses are more powerful.

Hypnosis, meditation, and prayer, examples of mind-body intervention, are another type of CAM. A number of studies have documented physiological changes during meditation, and from personal experience I can tell you it is extremely relaxing. Prayer is harder to nail down; one study showed it helped people who were being prayed for even though they didn't know it.

Special diets, herbs, and other supplements are biologically based CAM therapies. This category includes some good ones (St. John's wort may help improve mild depression), some bad ones (too much ma huang can lead to stroke or death), and some ugly ones (shark cartilage and laetrile do nothing except dent your wallet). I spend time discussing some aspect of this category with just about all of my patients.

Massage is an example of a manipulative body-based therapy, as is chiropractics--did you know that two-thirds of the country's HMOs cover chiropractic care? Energy therapies, yet another form of CAM, include Qi Gong, Reiki, and Therapeutic Touch. According to traditional Chinese medicine, Qi Gong employs movement, meditation, and breathing to enhance the flow of Qi.

If you're considering a CAM therapy, find out what's known about it, if it's safe, and what it costs. For some problems, CAM may not be the best choice. Bloodletting and leeches seemed like a good idea 200 years ago; George Washington probably hastened his death by donating a few pints.

The other thing to remember is that CAM is dynamic. As supportive data accumulates, what was alternative yesterday may become mainstream tomorrow. If CAM sounds interesting, strike up a dialogue with your medical doctor if he or she is open. Above all, remember the doctrine of Hippocrates--primum non nocere--which, loosely translated, means "do no harm." If your appendix just burst, do yourself a favor: Can the CAM and get thee to a surgeon.

For more information on this topic: Go to mayoclinic.com. Mayo Clinic offers Executive Health programs at Mayo Clinics in Jacksonville, Fla.; Rochester, Minn.; and Scottsdale, Ariz.

Donald D. Hensrud, M.D. Director of the Mayo Clinic Executive Health Program