The 10 most popular nonvitamin, nonmineral natural products used in the United States: Echinacea Source: Purple coneflower, a medicinal...

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The 10 most popular nonvitamin, nonmineral natural products used in the United States:

Echinacea

Source: Purple coneflower, a medicinal plant native to North America.

Estimated users (2002): 14.7 million.

Medical uses: To prevent or treat symptoms of colds or flu; boost immune system.

Clinical verdict: America’s best-selling herbal medicine might be no better than a placebo. A study published in July in the New England Journal of Medicine found no significant differences among 437 volunteers, some who were infected with cold viruses and treated with 300-milligram doses of echinacea or placebos. Critics of the study contend the echinacea dosage was too low to be effective.

Adverse effects: Few side effects reported. Could cause allergic reaction, especially in people sensitive to ragweed and related plants.

Ginseng

Source: Root of ginseng, a perennial herb.

Estimated users: 8.8 million.

Medical uses: To control diabetes, to treat fatigue. Asian ginseng has been used for thousands of years as a general body tonic.

Clinical verdict: Limited research suggests ginseng might help reduce blood-sugar levels after meals. Many different species are grown in Asia and North America, making uniform clinical studies difficult.

Adverse effects: Can increase the stimulant effects of caffeine.

Ginkgo biloba

Source: Leaf of the ginkgo biloba, among the world’s oldest living trees.

Estimated users: 7.7 million.

Medical uses: To treat memory and circulation problems.

Clinical verdict: No conclusive evidence exists that ginkgo biloba prevents or treats Alzheimer’s disease. A 2002 study published in the Journal of the American Medical Association found it did not enhance memory in older, healthy people. A study funded by the National Center for Complementary and Alternative Medicine on whether ginkgo biloba prevents or delays mental decline in people 85 and older is being completed.

Adverse effects: Could impede blood clotting, especially taken with aspirin. Stop taking before surgery to minimize the chance of excessive bleeding. Might interact with psychiatric drugs and drugs that affect blood-sugar levels.

Garlic

Source: Garlic bulb.

Estimated users: 7 million.

Medical uses: To lower cholesterol levels and blood pressure.

Clinical verdict: Studies have found small, but statistically significant, short-term reduction in cholesterol in patients taking garlic preparations. For reasons that aren’t clear, the benefits don’t seem to last beyond six months. Garlic is far less effective in reducing cholesterol levels than are prescription drugs.

Adverse effects: Generally safe. Can reduce the effectiveness of other drugs, including cyclosporin, an anti-organ rejection medication, as well as antiviral HIV drugs. Can interfere with blood clotting and cause upset stomach.

Glucosamine

Source: Shell of crabs and other shellfish.

Estimated users: 5.3 million.

Medical uses: To treat osteoarthritis, also known as degenerative joint disease.

Clinical verdict: Occurs naturally in and around cartilage. Researchers believe it inhibits inflammation and promotes the growth of cartilage cells. Studies generally have shown that glucosamine works well for pain and symptoms of osteoarthritis and that it might help slow the disease’s progress. Glucosamine is often paired with chondroitin, another natural substance.

Adverse effects: Generally safe. Might cause diarrhea or constipation.

St. John’s Wort

Source: St. John’s, a perennial weed.

Estimated users: 4.4 million.

Medical uses: To treat depression, anxiety.

Clinical verdict: Can be effective in relieving symptoms of mild depression. Evidence is less conclusive about whether St. John’s Wort works on severe depression. However, a study published in February in the British Medical Journal found it worked at least as well as the prescription antidepressant paroxetine (Paxil) for moderate to severe major depression. What’s more, patients taking St. John’s Wort suffered fewer side effects, such as dry mouth and dizziness.

Adverse effects: Reduces the effectiveness of other medications by speeding up their elimination from the body. Organ-transplant patients taking the anti-rejection drug cyclosporin along with St. John’s Wort have suffered organ rejection. Should not be taken by anyone on anti-HIV drugs, birth-control pills, hypertension medication and other drugs because of the possibility of serious interactions.

Peppermint

Source: Oil extracted from the peppermint plant.

Estimated users: 4.3 million.

Medical uses: To treat irritable bowel, indigestion.

Clinical verdict: Evidence suggests peppermint acts to reduce gas and thus relieves symptoms of irritable-bowel syndrome, including abdominal pain, flatulence and diarrhea.

Adverse effects: Generally safe. Should not be taken by anyone with liver disease or obstructed bile ducts. Should not be applied under the nose of infants and young children because it could cause a temporary halt to breathing.

Fish oils/omega fatty acids

Source: Polyunsaturated fats found in cold-water fish such as tuna, salmon and mackerel.

Estimated users: 4.2 million.

Medical uses: To lower high cholesterol, high blood pressure.

Clinical verdict: The Food and Drug Administration allows supplement makers to make “qualified health claims” for omega-3 fatty acids. The FDA says research is “supportive but not conclusive” that consuming fish oils — either through supplements or in fish — helps reduce the risk of coronary heart disease.

Adverse effects: Tuna, catfish, pollock and many other fish can contain mercury, a pollutant that can cause neurological problems in fetuses and young children. Pregnant women, nursing mothers and young children are advised to limit consumption of fish. Fish-oil supplements should not contain any mercury.

Ginger

Source: Root of the perennial ginger plant.

Estimated users: 3.8 million.

Medical uses: To treat nausea and vomiting.

Clinical verdict: Considered effective against pregnancy-related nausea. Limited data suggest it might also prevent motion sickness. A study funded by The National Center for Complementary and Alternative Medicine is under way to determine whether ginger and turmeric can reduce inflammation associated with arthritis and asthma.

Adverse effects: Generally safe, but it can interfere with blood clotting if taken in large amounts. Could cause heartburn.

Soy supplements

Source: Soybean plant.

Estimated users: 3.5 million.

Medical uses: To control cholesterol; to control, treat heart disease.

Clinical verdict: Controlled clinical studies have shown that soy protein helps lower total cholesterol levels and low-density lipoprotein (“bad” cholesterol). The FDA in 1999 allowed makers of soy-based foods to tout soy’s health benefits on the label. To do that, the food must contain at least 6.25 grams of soy per serving and be low in fat and cholesterol.

Adverse effects: Generally safe.

Sources: National Center for Complementary and Alternative Medicine and Office of Dietary Supplements (both part of the National Institutes of Health); University of Washington School of Medicine, Department of Family Medicine; American Botanical Council; The Dietary Supplement Education Alliance; National Center for Health Statistics; Seattle Times research.