Flawed Meta-Analysis Misrepresents Vitamin E Research
 
   

Flawed Meta-Analysis
Misrepresents Vitamin E Research

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:
   Frankp@chiro.org

 
   

Thanks to Cindy Latham for sharing this information!


A recently published report in the online edition of the Annals of Internal Medicine (Nov. 10, 2004) alleges that high doses of Vitamin E may increase the risk for mortality, and the report has been widely disseminated this week by the media.  The Council for Responsible Nutrition and other scientific experts disagree with the conclusions of the study which is the basis for this report. In addition, the National Institutes of Health and the Institute for Medicine, which sets the recommended daily allowance for vitamins in the United States, both state that Vitamin E is safe.


Why the Study Is Flawed

There are significant flaws and inaccuracies in this meta-analysis conducted by researchers from Johns Hopkins University.  A meta-analysis is not a new study.  It is simply a compilation of previously run large-scale clinical studies.  Scientific experts have noted major problems with the author's conclusions drawn from this meta-analysis, which ignored the vast majority of existing published studies, for the following reasons:

  • There was a bias in the selection of the studies to review. The researchers selected only 19 of the 2,170 studies available on Vitamin E

  • Eighteen of the 19 studies reviewed did not support the researcher's conclusions. The only study that did support their conclusions was a hormone replacement therapy study that examined the effects of using Vitamin E and estrogen in combination, which confuses the results of this study.

  • Less than half of the studies reviewed were done on Vitamin E alone.

  • Additionally, studies using higher than 400 IU were done on diseased populations, whereas studies using less than 400 IU we done on healthy people.

  • While the authors concluded that Vitamin E supplementation did not affect all-cause mortality (death risk), with no supporting data they recommended that people should not exceed a daily dose of 400 IU.

  • The National Institutes of Health (NIH) and the Institute of Medicine, which sets recommended daily dietary guidelines for vitamin supplements, have identified the tolerable upper level of natural Vitamin E intake at 1500 IU/day for adults. The Institute of Medicine defines the upper limit as "the maximum intake of a nutrient that is likely to pose no risk of adverse health effects in almost all healthy individuals in the general population."


Dr. Jeffrey Blumberg, Associate Director of Tufts University Human Nutrition Research Center on Aging, and widely recognized nutrition expert, emphasized that the research used in the study looked at people already at high risk of death, which can't be used to determine what's good for healthy people.

Dr. Blumberg also stated that these investigators selected 19 specific studies to analyze. In doing so, they also selected not to employ a vast number of studies that show no harm from Vitamin E and a great deal of benefit.

In reaching their conclusions, the authors ignored a huge body of research that supports the health benefits of Vitamin E supplementation.


Vitamin E Is Safe and Effective

There are more than 1,000 studies that support the safe and efficacious use of Vitamin E supplements, including several studies that were reviewed in this recent analysis.  Research studies on Vitamin E supplements have linked the antioxidant to numerous health benefits including reduced progression of advanced age-related macular degeneration, reduced occurrence of cataracts, slowing the progression of Alzheimer's disease, slower progression of atherosclerosis, lower incidence of non-fatal myocardial infarction, and reduced incidence of upper respiratory infection, to name just a few.

For instance:

  • 1993 – supplementation with vitamin E was associated with a 30-40% reduced risk for coronary disease in a study of 90,000 nurses (Nurses Health Study; NEJM 328:1444-1449)

  • 1993 – total vitamin E intake is inversely related to the risk of colon cancer; those with a highest vitamin E intake had the lowest incidence of colon cancer (Iowa Women's Health Study; Cancer Res:53:4230-4237)

  • 1994 – Levels of vitamin E intake were inversely correlated with coronary deaths in both women and men in a large (>5000 people), long-term (14 year follow-up) Finnish study (Am. J. Epidemiol. 139:1180-1189).

  • 1997 – A review of the literature concerning vitamin E and breast cancer concluded "although epidemiologic study results have been inconsistent, further study of this nontoxic vitamin is warranted." (Nutr. Cancer 27:109-117).

  • 2000 – supplementation with Vitamin E supplementation may prevent ischemic stroke in high risk hypertensive patients (Arch Neurol. 57:1503-1509; analysis of data from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study)

  • 2004 – protective effect of vitamin E supplementation on upper respiratory tract infections in elderly nursing home residents (JAMA 292:828-836)

  • 2004 – supplementation with vitamins E and C in combination is associated with reduced prevalence and incidence of Alzheimer Disease (Arch. Neurol. 61:82-88; this study is from Johns Hopkins)

  • FDA – allows qualified health claim regarding "consumption of antioxidants (including Vitamin E) and reduced risk of some forms of cancer."

This week's headlines aside, the preponderance of scientific and clinical data shows well-established benefits of Vitamin E for otherwise healthy individuals. Supplementation with vitamins, including Vitamin E, makes sense in support of a healthy lifestyle, and for people who desire nutritional insurance for the gaps left unfilled by the typical diet.


For more information about the recent news on Vitamin E, please visit the Web site for the Council on Responsible Nutrition, which also questions the conclusions reached by the researchers.


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