March 8, 2007 – Therapeutic use of certain antioxidant supplements may increase death rates, say Danish researchers whose work was published in the Journal of the American Medical Association (JAMA)1.
These researchers, associated with the prestigious Cochrane Hepato-Biliary Group, analyzed the results of 68 clinical trials conducted on 232,606 subjects. In each of these trials, one group received a supplement containing one or more antioxidants (beta-carotene, vitamin A, vitamin E, vitamin C or selenium, taken alone or in combination), while another group took either a placebo or none. extra charge.
The participants suffered from various illnesses (coronary or cardiovascular disorders, Parkinson’s disease, etc.). They were sometimes smokers or alcoholics, some were elderly living in reception centers and a few were healthy individuals who did not fall into any of these categories. For the analysis, we counted the deaths which occurred during the tests, whatever the cause.
The results indicate that 13% of participants who took an antioxidant supplement died compared to 10.5% of those in the control groups. After eliminating the trials they deemed “at high risk of bias”, the researchers arrive at 15.5% of deaths on the side of those who took a supplement, against 11.2% in the controls.
According to Jean-Yves Dionne, pharmacist, there are too many variables in this meta-analysis for a clear conclusion to be drawn. “The authors,” he says, “have chosen to combine trials conducted with or without a placebo, studying the effects of five different substances, taken alone or in combination, as the case may be, on groups of completely heterogeneous subjects. These variables all have their share of bias and can therefore, if not taken into account, distort the results. “
Jean-Yves Dionne also points out that one of the five substances studied, vitamin A, is not considered to be an antioxidant. This vitamin, taken in excess, can have toxic effects on the body. “One can wonder about the reasons which prompted the researchers to include this substance in their analysis. “
According to the results of Danish researchers, vitamin C and selenium are not associated with an increase in mortality. This risk would mainly target beta-carotene and vitamins A and E.
Data from other studies indicate that beta-carotene, a precursor to vitamin A, may be harmful to smokers if taken in high doses.2. As for vitamin E, the results of meta-analyzes vary between researchers: depending on how they analyze the data, some conclude that a high dosage can be fatal.3 while others find this vitamin safe in most cases4.
Pierre Lefrançois – PasseportSanté.net
1. Bjelakovic G, Nikolova D et al. 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.
2. Siems W, Wiswedel I, Salerno C. Beta-carotene breakdown products may odd mitochondrial functions – potential side effects of high-dose beta-carotene supplementation. J Nutr Biochem. 2005 Jul; 16 (7): 385-97. Review.
3. Miller ER 3rd, Pastor-Barriuso R et al.Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality. Ann Intern Med. 2005 Jan 4; 142 (1): 37-46. Epub 2004 Nov 10. Full text: www.annals.org
4. Hathcock JN, Azzi A et al. Vitamins E and C are safe across a broad range of intakes. Am J Clin Nutr. 2005 Apr; 81 (4): 736-45. Full text: www.ajcn.org
