It's not exactly a secret that Americans have leapt ahead of the science on alternative medicine, trying supplements and therapies -- such as echinacea for colds and yoga for back pain -- without waiting for proof of their efficacy. But just how far ahead they've gotten became clear earlier this month when the National Center for Complementary and Alternative Medicine (NCCAM) released a survey showing that more than one-third of American adults used some kind of complementary and alternative medicine in the past year. Broadening the definition of alternative health to include prayer raised the figure to nearly two-thirds.

The willingness of Americans to experiment on themselves generated $49.6 billion in supplement sales and payments to alternative health care providers in 2002, according to the Nutritional Business Journal, an industry publication.

Some researchers say it's time for the science to catch up with this hefty market -- especially since not all of these treatments can be presumed to be harmless. Experts caution that people should be sure to tell their doctors when they try herbs or other therapies, and people should not use alternative medicines or treatments in lieu of safe and effective conventional care.

But do the most frequently used alternative treatments really work? In many cases, it's hard to say. Because most mainstream medical researchers have shown little interest in studying alternative healing methods and because funding for large-scale research has been scarce, controlled, randomized studies are rare. The NCCAM is trying to change that. The center, which was established by Congress in 1998 and is part of the National Institutes of Health, will spend an estimated $103.5 million in 2005 to fund scientific studies into alternative and complementary medicines and treatments. Government funding for the center has risen from $50 million in 1999 to $117 million this year.

Meanwhile, we examined 10 therapies that placed high on NCCAM's survey to see what the best science currently shows about their efficacy.

Echinacea

After prayer -- a special case that we'll return to later -- herbs and other "nonvitamin, nonmineral, natural products" are the alternative therapies Americans turn to most, used by a quarter of the more than 31,000 adults interviewed for the NCCAM survey. And among such products, echinacea is the hands-down favorite, used by 40 percent of this smaller group. That places it in the top 10 therapies used in the survey.

Native Americans used echinacea, made from the root and other parts of the coneflower, for various ailments, and some German studies have shown that doses of echinacea can stimulate parts of the immune system. Today, users mostly take the herb in pill or liquid form in hopes of warding off or reducing the severity of the common cold.

Bruce Barrett, a researcher with the University of Wisconsin-Madison Department of Family Medicine, said evidence for the use of the herb as a natural cold medicine is mixed. While some small, older studies suggested that echinacea reduces the symptoms and duration of the common cold, several larger, more recent studies found no effect. (This includes one of Barrett's own studies, published in December 2002 in the Annals of Internal Medicine.) A study published this month in the Archives of Internal Medicine (and described in Quick Study, Page F8) also found that taking echinacea did not lessen the severity of colds or speed recovery. Another study, published in the December 2003 Journal of the American Medical Association (JAMA), found the herb didn't help children get over their colds faster or improve their symptoms.

According to the Mayo Clinic Web site, most forms of echinacea are unlikely to cause serious side effects if dosing instructions are followed. (Echinacea injections, which are not recommended by Mayo, can cause severe allergic reactions.) Some studies are examining whether echinacea may interfere with birth control medications.

Ginseng

The Chinese have used Panax ginseng, the root of Asian ginseng, for 2,000 years. In the United States, users generally take it in pill form, hoping to improve mental performance and concentration. Ginseng was the second most popular natural product in the NCCAM survey -- 24 percent of those who used herbal products had used it in the past year.

Some studies have shown that ginseng can improve reaction time and learning ability, but they haven't been well designed or reported, according to the Mayo Clinic Web site. Other studies have suggested that taking ginseng together with ginkgo biloba may boost brain power, but again the studies are small and not randomized or controlled.

Some athletes take ginseng to improve stamina, but here, too, the evidence is mixed. Several studies suggest ginseng may lower blood sugar in people with type 2 diabetes, but long-term effects and proper dosage haven't been studied.

"Well-conducted trials do not support the efficacy of ginseng to treat any condition," wrote Edzard Enrst, a British researcher, in a 2002 review article in the Annals of Internal Medicine.

While serious side effects are rare, some people taking ginseng have reported diarrhea, sore throat, excitability, anxiety, depression or insomnia. Because ginseng may have some estrogen-like effects, the Mayo Clinic recommends that people with hormone-sensitive conditions -- such as breast or uterine cancer -- avoid ginseng. Some case reports suggest ginseng may thin the blood, making it potentially dangerous for people on blood-thinning medications like warfarin.

Ginkgo Biloba

Imagine if a natural product could prevent Alzheimer's disease and dementia or even improve concentration and memory. Extracts from the leaves of the ginkgo biloba tree, imported to the United States from China in 1784, can do all that, some say, plus relieve a multitude of other ills, including altitude sickness, premenstrual syndrome, impotence, depression and glaucoma.

All this may explain why ginkgo is one of the top-selling herbs in the United States, accounting for some $130 million in sales in 2003, according to the Nutrition Business Journal. Ginkgo was the third most popular natural product in the NCCAM survey; 21 percent of those who took herbal supplements reported taking it.

But does it work? "Ginkgo extract has a number of chemical activities that theoretically keep dementia away, but you've got to do the study to see," said Steven DeKosky, chairman of the department of neurology at the University of Pittsburgh School of Medicine. A 1997 study in JAMA found ginkgo could improve cognitive performance in people with dementia. But a rigorous 2004 review by a the Cochrane Collaboration, a U.K.-based nonprofit group that analyzes data from clinical trials, recommended further study, despite what it called "promising evidence" of benefit.

With the help of NCCAM funding, DeKosky is conducting the largest ginkgo trial ever, which will follow 3,000 people with normal mental function or mild cognitive impairment over at least five years. In addition to tracking how many subjects develop dementia, researchers hope to learn whether ginkgo could decrease heart attacks, strokes and related deaths.

Because ginkgo may change insulin and blood sugar levels, people with diabetes or hypoglycemia should consult a doctor before using it. Some studies suggest ginkgo may increase bleeding, making it dangerous for people with bleeding disorders or on blood-thinning drugs. Ginkgo seeds are poisonous and can cause seizures.

Garlic Supplements

Promoters say garlic can lower cholesterol and blood pressure, prevent hardening of the arteries and protect against cancer. Skeptics say it's as likely to keep away vampires.

The Agency for Healthcare Research and Quality, a federal agency that develops evidence-based reports on medical treatments, conducted a systematic review of the evidence and found that while garlic supplements may temporarily lower LDL ("bad" cholesterol), it doesn't appear to to raise HDL ("good" cholesterol) or confer long-term protection against heart disease. The agency found no proof that it lowered blood pressure or treated diabetes and called the evidence on cancer prevention inconclusive.

Other than smelly breath and body odor, possible adverse effects associated with garlic include abdominal pain, asthma and intestinal obstruction. A few studies suggest garlic may cause bleeding or blood-thinning, so garlic supplements are not recommended for people who are on blood-thinning medication. Severe allergic reactions are also possible.

One challenge to studying garlic is the many forms in which it's available -- cooked, raw, mashed and in supplements. Christopher Gardner, director of nutrition studies at the Stanford Prevention Research Center, is trying to allow for possible differences in effectiveness by giving 200 people with moderately elevated cholesterol either fresh garlic, one of two types of garlic supplements or a placebo every day for six months. A previous Gardner study found at least one garlic supplement did not lower cholesterol, but he's not finished exploring the possibility that some form of garlic has a cardiovascular benefit.

"It's biologically plausible that [herbs like garlic, ginkgo and ginseng] can help people," he said, "but . . . it doesn't mean that it works. When you do these clinical trials, it takes dozens of them to show something."

Deep Breathing

Deep breathing is an integral part of meditation and yoga, but some alternative practitioners teach deep breathing alone to calm the mind and body. Plenty of people are trying it -- 11 percent of respondents to the NCCAM survey reported trying it for health reasons in the past year -- more than any of the other "mind-body therapies" in the survey except prayer.

David Spiegel, medical director of the Center for Integrative Medicine at Stanford Medical Center, said his center uses deep breathing therapy mainly to help patients with stress and anxiety disorders.

"The problem with modern humans is that our stress response is a physical one," Spiegel said. "When we prepare our bodies to fight or flee, we tend to get hyper-aroused." Deep breathing, he said, can help people regulate their stress levels and heart rate.

A few small studies in Israel have found that sessions of slow, deep breathing can lower blood pressure in people with high blood pressure. But large, randomized, controlled studies on the health effects of deep breathing are rare. On the other hand, no studies appear to report negative side effects.

Meditation

People have sought mental calm and physical relaxation through meditation for thousands of years, but only recently have researchers begun to study meditation's effect on the brain. The NCCAM survey found that 7.6 percent of respondents had tried meditation in the past year.

Andrew Newberg, a neuroscientist involved in studies of the practice at the University of Pennsylvania Medical School, says meditation may improve immune system function and affect dopamine and serotonin levels, which affect feelings of well-being.

A few studies have shown meditation may help reduce blood pressure and relieve pain from arthritis and other conditions, but because study participants also received biofeedback and other alternative therapies, it's hard to say how much of the effect was due to meditation. A meta-analysis published last year in the Journal of the American Board of Family Practice similarly reported that fibromyalgia patients may benefit from a combination of meditation and other therapies.

While the link between meditation and disease prevention or treatment is still tentative, some practitioners use meditation in clinical settings. The program for stress management at the University of Pennsylvania, for example, teaches meditation in hospitals, schools and violence prevention programs.

NCCAM is funding clinical trials on the use of meditation and other alternative therapies to treat rheumatoid arthritis, binge eating disorder and cardiovascular disease. In addition, the center is partnering with the National Heart, Lung, and Blood Institute and the National Institute on Aging to study the effect of meditation and health education on heart disease in African American women age 60 and over.

Chiropractic

Some mainstream doctors may view it as a fringe treatment, but chiropractic is more commonly covered by insurance than any other type of alternative care. About 95 percent of PPOs and 80 percent of HMOs provide some coverage for chiropractic care, according to the American Chiropractic Association. An estimated 30 million Americans visit chiropractors each year -- mostly for low back pain. In the NCCAM survey, 7 percent of respondents reported receiving chiropractic care in past 12 months; 20 percent reported ever having gone to a chiropractor.

Do the treatments help? Depends on whom you ask.

A Cochrane Collaboration meta-analysis published last year in the Annals of Internal Medicine suggested that spinal manipulative therapy worked better than sham manipulation and discredited therapies at relieving acute or chronic low-back pain. But researchers found no evidence spinal manipulation was better than other standard treatments.

William Meeker, director of the Palmer Center for Chiropractic Research in Davenport, Iowa, which has received NCCAM funding, said researchers don't yet fully understand the exact biomechanism by which spinal adjustments might relieve pain. One theory, he said, is that bombardment of impulses to the sensory system modifies pain sensation; another is that spinal manipulation changes the way joint surfaces interact with each other.

Side effects of chiropractic treatment, Meeker said, can include muscle soreness and pain. One maneuver to the upper cervical spine has been implicated in strokes, but the incidence is very rare, he said.

Yoga

The ancient practice that combines deep breathing, meditation and stretching has become wildly popular in the past several years. According to a 2003 survey by Yoga Journal magazine, 15 million people -- mostly women -- practice yoga in the United States. Among respondents to the NCCAM survey, 5 percent had tried it within the last year.

Most Americans practice yoga for fitness and stress reduction, but Mary Lou Gallantino, a physical therapist who researches yoga at the University of Pennsylvania Medical School, said more people are turning to yoga as therapy. Some of the most common ailments that she said send people to their yoga mats: depression, anxiety, hypertension, asthma and back pain. A study published this month in the journal Neurology found that people with multiple sclerosis who practiced yoga for six months significantly reduced fatigue levels.

Other studies have found that yoga may help with chronic low back pain, sleep problems and hypertension. Harvard researcher Sat Bir Singh Khalsa has found yoga reduces the levels of stress hormones in some people, allowing them to fall asleep more easily even after they discontinue yoga exercises.

"It's a very good treatment for stress-related disorders," Khalsa said. Gallantino said she used yoga to help her through her recent battle with breast cancer. "It assisted with the side effects of chemotherapy for me. I was fully functional, and I didn't have any major energy loss," she said. "I was able to weather the storm."

Some people do injure themselves while trying to contort themselves into yoga positions, and bikram, or "hot," yoga is not recommended for people with heart conditions or who have had previous problems with heat cramps or heatstroke.

Massage

In the NCCAM survey, 5 percent of respondents reported using massage therapy in the last year.

Small studies have suggested that massage can reduce anxiety and perception of pain in cancer patients, promote sleep in critically ill patients and increase relaxation, energy and mobility in residents of long-term care facilities, but most studies on massage haven't been replicated in an effort to confirm their findings. One 2003 review published in the Annals of Internal Medicine found that massage is effective for chronic back pain, but a 2004 review by Edzard Ernst in the Clinical Journal of Pain found insufficient evidence to recommend massage for controlling musculoskeletal or other pain.

NIH nurse Jim Nichols finds massage helpful for people with terminal illnesses and chronic pain. "A lot of times when I work with people with terminal illnesses, they tend to take their mind away from their body," Nichols said. "What I try to do is let them reconnect with themselves and be able to calm down and come back into their body."

A 2003 review in the journal Rheumatology found that although massage is not entirely free of risks, most reported problems with massage were associated with "exotic types of manual massage or massage delivered by laymen."

Prayer

If meditation, yoga and deep breathing may help people use their minds to heal their bodies, what of the power of faith? The NCCAM survey found that 43 percent of people pray for their own health and 24 percent have had others pray for their health in the previous year -- a total of 45 percent reported some sort of prayer for health reasons.

Prayer was by far the most common alternative treatment in the survey.

But can we measure the power of prayer? Studies have found that people who regularly attend church live longer than those who don't, but the fact that they smoke less and tend to be less depressed may account for their durability. People who have others praying for them when they are ill also tend to have the personal relationships that have proven health benefits. Is it possible to separate prayer from other factors to see whether prayer alone can affect people's health?

Duke cardiologist Mitchell Krucoff studied 750 patients undergoing heart catheterization or angioplasty. Preliminary results showed that one group of patients who were prayed for by multiple prayer groups (Roman Catholics in the United States, Buddhist monks in Nepal, Jews in Israel) did no better than a group that received standard care or a third group that received therapies including guided imagery, music, stress relaxation or touch therapy. A fourth group, which received both prayers and the relaxation therapies, however, showed a significant reduction in death rates compared with the other therapies.

"The combination of the bedside therapies and the prayer intervention creates a trend to improve survival," Krucoff said.

The study of prayer as a health intervention raises ethical questions -- as well as theological ones, such as: Do the prayers of 1,000 strangers count more than those of a mother at her sick child's bedside? -- but some researchers say prayer is worth studying.

"There is an association with spirituality, religious practice and prayer that all seem to have an impact," Baime said. "If we really believe in the scientific method, it's worth investigation. Otherwise we're just blowing hot air."

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Elizabeth R. Agnvall last wrote for the Health section about health club fitness legislation. Staff writer January Payne also contributed to this story.