If you have been reading the papers this past fortnight you may have happened upon articles claiming that antioxidants â more familiarly known as Vitamins A, C and E, selenium and beta-carotene (among others) â are more enemy than friend when it comes to preserving your health.
Such reports stemmed from the recent re-publication of the Cochrane review, first published in 2005 by the Cochrane Collaboration, a widely read source of information on health matters that regards itself as reliable and evidence-based. The paper, which purports to be a meta-analysis of established research relating to the impact of antioxidants on health, concluded that antioxidants, far from preventing you from rusting, were actually linked to a higher risk of mortality.
But there appears to have been a problem with at least one major aspect of the review.
Reviewers considered 452 established studies on antioxidant vitamins but then threw out the 405 studies in which nobody died! This left 47 studies from which to draw conclusions. In each of the 47 studies, subjects had died from a variety of causes. For example, one study was conducted with terminal heart patients, another with cancer patients. From this severely limited selection of studies, the Cochrane review researchers concluded that antioxidants increased mortality.
Hmmm! So it was the vitamins, then? Not the cancer or the heart disease? And thatâs quite apart from the dilemma posed by the exclusion of studies which may show vitamins enhancing health and keeping the Grim Reaper from the subjectsâ doorâ¦
In addition to this major methodological flaw, it transpires that the researcher responsible for one of the studies on which the Cochrane review was based now says she arrived at the wrong conclusion in her original study. The study, which made headlines when published, found that cancer patients who took either Vitamin A (beta-carotene) or Vitamin E (alpha tocopherol) supplements were 40 per cent more likely to witness a return of cancer than those who took no supplements at all. More recently, however, Isabelle Bairati and her team from the Quebec Research Centre re-analysed their original data and discovered that the only people suffering a return of cancer were smokers who had refused to kick the habit while receiving radiotherapy or chemotherapy. (Source: International Journal of Cancer, 2008: 122: 1679-83)
Not quite the same thing as antioxidants being responsible for increased mortality, and not remotely as sexy, for the media has so far failed to run with the correct (and more prosaic) version of eventsâ¦
For more information, visit the following web sites:
http://www.cochrane.org/reviews/en/ab007176.htmlfor a summary of the review, or click on the Cochrane Library link for the full text.
Joined: Tue Feb 12, 2008 2:29 pm