Blackmores Dismisses Flawed Antioxidant Research
Thursday, March 1st 2007
Blackmores has assured Australian vitamin-takers not to be concerned by alarmist conclusions drawn in the Journal of the American Medical Association (1) claiming that certain antioxidant vitamins can increase the risk of death.
Experts who reviewed the study were dismissive of the reported conclusion, saying the research pooled studies that were too diverse. The doses used in many of the studies were significantly higher than those allowable in Australia and New Zealand. Many of the studies were done on high risk populations including smokers and those exposed to asbestos which would have an increased risk of death.
The research is actually a meta-analysis, in which the findings from a range of studies done for different purposes are grouped together in an attempt to draw a conclusion. While meta-analyses are appropriate when the included studies are very similar in design and study population, this meta-analysis combined studies that differ in so many ways that the results would be compromised.
"There is no new clinical data in this publication - it is an overall synthesis of existing data from multiple trials, in multiple disease states and with multiple dosages and combinations - this is its main problem," said Blackmores' Research Director Chris Oliver.
"The fact that this analysis includes numerous disease conditions, and supplements at various doses, composition, and duration of administration, makes any conclusions meaningless," said Qing Jiang, PhD, Assistant Professor, Department of Foods and Nutrition, Purdue University in a statement released in response to the study. "The majority of patients were on multiple prescription medications, which further invalidates the results.
"The ages of the patients in the trials ranged from 18 to 103, with significant variability in health status that was not accounted for. In addition, many of the patients were smokers, a risk factor associated with high mortality."
The trials with vitamin A are skewed by two large trials (the largest trial was in smokers or those exposed to asbestos) of people taking 25,000 IU for over 3 years. Current Australian TGA mandated limit for supplements is set at 5,000 IU per day.
There is a significant body of robust clinical evidence to support the benefits of antioxidants. In a recent prospective cohort study of over 80,000 Swedes, high levels of vitamin A (and beta-carotene) intake were found to be protective against gastric cancer. Interestingly, these effects were seen only in non-smokers or former smokers(2).
1) Bjelakovic G et al. Mortality in Randomised trial of Antioxidant Supplements for Primary and Secondary Prevention. JAMA, February 28 2007 Vol 297, No 8.
2) Larsson SC, Bergkyist L, Naslund I et al. Vitamin A, retinol, and carotenoids and the risk of gastric cancer: a prospective cohort study. Am J Clin Nutr. 2007, 85:497-503.
Source, Australian Press Release Issued Regarding Antioxidant Research: Last night 28 February 2007 on One News there was a story claiming that vitamin supplements increased the risk of death. The coverage was based on a meta-analysis published in the Journal of the American Medical Association.
Footnote from Ideal Health:
The following products are all useful Antioxidants:
Enzogenol with ACE and Selenium
Resveratrol Age Defence
Vitamin C with Hesperidin Complex
Vitamin E 500 IU
Related health information can be found here:
Glutathione - the master antioxidant involved in disease prevention
Pycnogenol - a powerful antioxidant from pine tree extract
Smart nutrients for better brain function
Vitis, a powerful antioxidant derived from grape seeds
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