By James J. Gormley
Lately we’ve heard quite a lot about how nutritional supplements, including antioxidant vitamins, are regarded by a few scientists as a great danger—or so we might gather from recent media coverage that has treated us to such fear-mongering headlines as “Potential for harm in dietary supplements”(1), “Vitamin pills may do more harm than good” (2) and “Why some popular pills might kill you” (3). The scientific review to which these sensationalistic stories refer was a meta-analysis in the Cochrane Database of Systematic Reviews (4).
A meta-analysis is supposed to be careful re-review of many studies whose results are pooled together. The Cochrane Database meta-analysis, authored by Goran Bjelakovic and others, is an updated version of a review that originally appeared in the Journal of the American Medical Association (5) that had been roundly criticized by scientists.
While 67 clinical trials were included in this new review, most people are not aware that 748 trials were excluded for a number of reasons, including 405 studies that failed to show anybody died (6).
One could persuasively argue that the authors of this review only included studies which could be molded to support the viewpoint that antioxidant vitamins are dangerous.
Dr. Bjelakovic has made no bones about his skeptical attitude towards dietary supplements. In 2007, he co-authored an article in the Journal of the National Cancer Institute entitled: “Surviving Antioxidant Supplements” (7) and has posted an article on a newspaper syndicate entitled “Do antioxidant supplements work?” (8).
While meta-analyses, when properly conducted, can be an insightful tool; when ill used they are subject to bias by those who hold pre-determined conclusions and are seeking a way to force studies into them.
A wide body of scientific evidence has established that taking antioxidant supplements — including vitamins C and E, beta carotene, selenium and zinc — can help reduce the risk of chronic disease. That being said, we know that antioxidant supplements (and supplements, in general) are not magic bullets, but they can be an important complement to a healthful diet.
If we twist science to create worldwide distrust in healthful dietary supplements, then we are truly harming consumers.
References
1. Brody J. Potential for harm in dietary supplements. New York Times April 8th, 2008.
2. Vitamin pills may do more harm than good. Scotsman UK. http://news.scotsman.com/health/vitamin-pills-may-do-more.3984844.jp
3. Why some popular pills might kill you. The Herald UK. http://www.theherald.co.uk/news/news/display.var.2199569.0.Why_some_popular_pills_might_kill_you.php
4. G. Bjelakovic, D. Nikolova, L.L. Gluud, R.G. Simonetti, C. Gluud. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD007176.
5. G. Bjelakovic, D. Nikolova, L.L. Gluud, R.G. Simonetti, C. Gluud. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA 2007 Feb 28;297(8):842-57.
6. Daniells S. The dangers of selective science. Nutraingredients.com April 12, 2008 [online news portal] http://www.nutraingredients.com/news/ng.asp?id=84792-meta-analysis-antioxidants-randomised-clinical-trials
7. Bjelakovic G and Gluud C. Surviving antioxidant supplements [editorial]. JNCI Journal of the National Cancer Institute 99(10):742-743, 2007.
8. Bjelakovic G. Do antioxidant supplements work? Project Syndicate [online]. http://www.project-syndicate.org/print_commentary/bjelakovic1/English
Sunday, May 04, 2008
Subscribe to:
Posts (Atom)
Posts
