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updated 12/11/2003 6:18:43 PM ET 2003-12-11T23:18:43

Another study has been released showing that consumers need to be cautious regarding advice they receive in health food stores. Researchers posing as typical consumers found employees of these stores readily giving information and product recommendations – often without mentioning possible adverse reactions or interactions with medical treatments.

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Cancer patients, who may see health food stores as the extra help they desperately want, should be especially cautious. The recent report in Breast Cancer Research involved visits to 34 stores where the researcher posed as someone whose mother had breast cancer. Overall, 33 different products were recommended. Of particular concern is the fact that 68 percent of the store employees never even asked what medical treatment was being used.

Surveys show that vitamin and herbal supplements, including antioxidants, are widely used by cancer patients. Yet it is unclear whether antioxidants help reduce side effects of cancer therapies and enhance chemotherapy’s effectiveness.

Some scientists caution that since many forms of treatment create oxidative damage to destroy cancer cells, antioxidants could actually interfere with treatment. The American Institute for Cancer Research is sponsoring a variety of studies to see how nutrition can enhance cancer treatments.

Meanwhile, AICR advises people receiving chemotherapy or radiation treatments to avoid antioxidant supplements for several weeks before and during treatment, unless advised otherwise by their radiation therapist or oncologist.

Because of the potential benefits from soy foods, many breast cancer patients assume that supplements containing genistein or other isoflavones found in soybeans would be helpful. Yet genistein may promote the growth of some estrogen receptor-positive tumors and reduce the effectiveness of the anti-cancer medicine tamoxifen.

For now, no clear recommendations exist about soy products for breast cancer patients. It may be helpful to remember that eating one or two servings of soy foods daily may have quite different effects than taking supplements with much higher doses of these phytoestrogens (weak plant forms of estrogen).

Many health food store employees advocated shark cartilage for cancer patients. Test tube and limited animal studies suggest such products may help block certain steps necessary for cancers to spread. Yet an AICR review of published research could find only a few human studies showing limited benefits.

It’s not just cancer patients who are at risk from following unfounded or incomplete advice in health food stores, either. Some weight-loss supplements that sales clerks recommend to the general public have no research support – some even pose potential health hazards.

Although some supplements may hold promise for prevention or treatment of various health problems, sound research is just beginning to emerge. Experts suggest that consumers interested in such products seek advice from authoritative sources that do not also sell them.

Consumers who want sound information about supplements can look on the Internet at or at http://www.aicr.org/.

Cancer patients seeking help sorting out nutritional options can keep up with the latest research findings through AICR at .

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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