Wednesday, May 24, 2006

That nostrum called supplements

From Quackwatch:

Comprehensive dietary supplement reports issued. The National Institutes of Health has drafted a "state-of-the-science" report about whether multivitamin/mineral supplements (MVMs) and certain single nutrient supplements can prevent chronic disease. The conclusions expressed by the report's authors include:

  • More than half of American adults take MVMs with the belief that they will feel better, have greater energy, improve health, and/or prevent and treat disease.
  • Compared with nonusers, supplements takers tend to have a better diet, less need for supplements, and more risk of exceeding the safe upper limit (UL) of some nutrients.
  • There is insufficient evidence to recommend either for or against the use of MVMs by the American public to prevent chronic disease.
  • Few high-quality studies have addressed whether one or a few nutrients can prevent chronic disease in American adults, and only a few such studies have yielded positive results.
  • With few exceptions, neither beta-carotene nor vitamin E had benefits for preventing cancer, cardiovascular disease, cataract, and age-related macular degeneration. Beta-carotene supplementation increased lung cancer risk in smokers and persons exposed to asbestos.
  • Folic acid alone or combined with vitamin B12 and/or vitamin B6 had no significant effect on cognitive function.
  • Selenium may confer benefit for cancer prevention but not cardiovascular disease prevention.
  • Calcium may prevent bone mineral density loss in postmenopausal women and may reduce vertebral fractures, but not non-vertebral fractures. The evidence suggests dose-dependent benefits of vitamin D with or without calcium for retaining bone mineral density and preventing hip and other nonvertebral fractures.
  • The FDA lacks the resources to collect adequate data and lacks the legal authority to safely regulate the dosage of individual ingredients.
  • Additional research and a mandatory adverse-event reporting system are needed for dietary supplements.

The draft statement was accompanied by a 321-page evidence report. A final statement is expected in July.

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