A study by Canadian researchers Eva Lonn, M.D., of the Population Health Research Institute and McMaster University, Hamilton Health Sciences Corporation, Hamilton, Ontario, Canada, and colleagues, has found from examining experimental and epidemiological data, that patients who took vitamin E supplements for 7 years did not significantly reduce their risk of cancer or cardiovascular events and some in fact had an increased risk of heart failure.
Previous clinical trials have generally failed to confirm benefits, possibly due to their relatively short duration.
The randomized, double-blind, placebo-controlled trial (Heart Outcomes Prevention Evaluation [HOPE]) was initially conducted between December 21, 1993, and April 15, 1999, and included patients at least 55 years old with vascular disease or diabetes mellitus. This trial was extended (HOPE–The Ongoing Outcomes [HOPE-TOO]) to between April 16, 1999, and May 26, 2003.
Of the initial 267 HOPE centers that had enrolled 9,541 patients, 174 centers took part in the HOPE-TOO trial. Of 7,030 patients enrolled at these centers, 916 were deceased at the beginning of the extension, 1,382 refused participation, 3,994 continued to take the study intervention, and 738 agreed to follow-up. Median duration of follow-up was 7.0 years. Patients received a daily dose of natural source vitamin E (400 IU) or matching placebo.
In both the trials the researchers found that the daily administration of 400 IU of natural source vitamin E for a median of 7.0 years had no clear impact on fatal and nonfatal cancers, major cardiovascular events, or deaths and they saw an increase in the risk of heart failure, which is worrying. The study data, although internally consistent, cannot be confirmed by other trials at this time, therefore this adverse effect of vitamin E warrants a meta-analysis of heart failure events including all completed large vitamin E trials. The researches recommend that in conjunction with its lack of efficacy, the potential for harm suggested by their findings strongly supports the view that vitamin E supplements should not be used in patients with vascular disease or diabetes mellitus. The study also has wider implications. There is a trend to accept 'natural products' (e.g., vitamins) as being safe, even if they have not been proven to be effective.The results of this study emphasizes the need to thoroughly evaluate all vitamins, other natural products, and complementary medicines in appropriately designed trials before they are widely used for presumed health benefits.