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Vitamin E is safe but ineffective, says new meta-analysis

By Nathan Gray , 24-Jan-2011

Supplementation with vitamin E is neither beneficial nor harmful in terms of mortality, according to the results of a new meta-analysis.

The analysis, published in Current Aging Science, re-examined the relationship between supplemental vitamin E (alpha-tocopherol) and all-cause mortality – finding that vitamin E supplementation is not associated with an increase in the risk of all-cause mortality.

“This random-effects meta-analysis of vitamin E and all-cause mortality based on 57 studies, which is the largest and most inclusive to date, shows that vitamin E supplementation is associated with neither a reduction nor an increase in the risk of all-cause mortality,” said the researchers, led by Erin Abner from the Sanders-Brown Center on Aging, at the University of Kentucky, USA.

The researchers said that– based on current evidence, supplementation with vitamin E “cannot be endorsed as a means of reducing mortality.”

“In the absence of evidence to the contrary, vitamin E supplementation should not be recommended as a means of improving longevity,” they said.

Evidence for E

Many chronic diseases associated with aging, such as cancer, cardiovascular disease, cataracts and dementia, have been linked to cellular damage from oxidative stress.

The authors said that in theory, powerful antioxidants, such as vitamin E in the form of alpha-tocopherol, may be able to treat or prevent conditions associated with oxidative stress.

They noted that some epidemiological studies and clinical trials of vitamin E have shown positive results, suggesting vitamin D may be beneficial for chronic disease. However, they said that these studies are in the minority.

Meta-analyses of vitamin E and chronic diseases – including liver diseases, gastrointestinal cancers, and cardiovascular disease – have found no relationship between supplementation and mortality or cause-specific deaths.

“Though vitamin E supplementation for prevention or treatment of disease has not been supported by the accumulated evidence, it is generally considered safe,” said the authors.

However, they said that data from recent meta-analyses on all cause mortality have been contradictory. Previous meta-analyses have for example found that the risk of all-cause mortality increases slightly, but significantly, for those taking more than 400 IU/d vitamin E, whereas other analyses – using almost identical data – have found no increased risk of mortality associated with vitamin E at any dose.

“The purpose of the current analysis is to re-examine the safety of supplemental vitamin E, particularly for older people, in light of additional evidence provided by several large trials,” said the researchers.

Study details

Abner and colleagues searched for randomized, controlled trials testing the treatment effect of vitamin E supplementation in adults for at least one year.

They identified 57 clinical trials published between 1988 and 2009 with a supplementation period of at least one year, and pooled the mortality data from each trial.

The trial had an average of 423 participants (ranging from 28 to 39,876) and lasted for an average of 2.6 years supplementation (ranging from one year to over 10 years)

Abner and co workers reported that the meta-analysis produce an overall risk ratio of 1.00 and suggested no relationship between dose and risk of mortality.

“Based on the present meta-analysis, supplementation with vitamin E appears to have no effect on all cause mortality at doses up to 5,500 IU/d,” said the researchers.

They said that their findings differ from two recently published meta-analyses of vitamin E and all-cause mortality, both of which found small but significantly increased risks of mortality for those taking supplemental vitamin E.

One possible explanation for the different findings is the number of included trials, they suggested. They added that the previous meta-analyses were performed on a smaller number of trials, and before data from several large, well conducted trials were available.

“If vitamin E does have an adverse effect on mortality, no biological mechanism has yet been identified,” said the researchers.

Source: Current Aging Science
Vol. 4, No. 2
“Vitamin E and All-cause Mortality: A Meta-Analysis”
Authors: E.L. Abner, F.A. Schmitt, M.S. Mendiondo, J.L. Marcum, R.J. Kryscio

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