Vitamin E meta-analysis misleads consumers
The following is an analysis by the scientific team of the Alliance for Natural Health, our international affiliate.
VITAMIN E STUDY MISLEADS CONSUMERS
Cautious interpretation is essential
The meta-analysis to be published next January in the Annals of Internal Medicine (Volume 142, Issue 1) , suggests that mortality in people taking over 400 IU of Vitamin E a day is increased. The study, published electronically on the journal’s website, re-analyses data from 19 clinical trials involving Vitamin E published between 1993 and 2004 and was undertaken by researchers at Johns Hopkins Medical Institutions.
In the view of the Alliance for Natural Health, which represents doctors, practitioners, consumers and leading-edge companies with interests in sustainable healthcare and natural therapies, it is of paramount importance that the study results are interpreted with caution.
Scaremongering headlines, based largely on misinterpretations of the study, which have begun to appear today, do nothing to help the development of responsible self-care patterns in consumers which are urgently required in the face of escalating heart disease and cancer rates.
Limitations of the study
In a widely circulated press release publicising the study, Dr Edgar Miller, lead author of the meta-analysis at Johns Hopkins University School of Medicine, claims that “If people are taking a multivitamin, they should make sure it contains no more than a low dose of vitamin E … our study shows that use of high-dose vitamin E supplements certainly did not prolong life, but was associated with a higher risk of death.”
However, the study has a number of very important limitations which mean that sweeping generalisations such as those made by Dr Miller should not be made. Such statements could be regarded as irresponsible particularly as they are likely to cloud consumer views over the importance of food supplementation as a means of compensating for the now well demonstrated inadequacies of the typical, western diet.
Some of the most important limitations of the study are:
·All trials in the study were performed using only one of the seven forms of Vitamin E, namely a-tocopherol, which is often used in its synthetic form. There is now strong scientific evidence which demonstrates that other forms of Vitamin E, as found in natural food sources, are much more effective as antioxidants, these being for example y-tocopherol and the four tocotrienol forms. While a-tocopherol has long been the yardstick by which vitamin E activity is measured, y-tocopherol, the most abundant form found in foods, has in recent years been demonstrated to have unique roles in the prevention of both cardiovascular disease and cancer (Stone WL and Papas AM, J Nat Cancer Inst, 1997; 89 (14): 1006-14).
·The studies were undertaken in the main on elderly persons suffering chronic diseases, so it is not possible to conclude that higher supplemental doses of Vitamin E promote disease or increase death among healthy people. This limitation is acknowledged in the Johns Hopkins study, the authors indicating, “we could not evaluate the generalizability of our findings to healthy adult populations.”
·Although the study includes 19 trials and is referred to as a meta-analysis, there is huge variation between the scale of the various trials and in the case of the 11 high dose trials, the bulk of the data come from just two large studies, namely the Cambridge Heart Antioxidant Study [CHAOS] and the Medical Research Council/British Heart Foundation Heart Protection Study [MRC/BHF HPS]. This latter study shows nearly double the number of deaths compared with all the other high dosage studies combined, and four times as many as in the other high dose studies with increased mortality. The study used a combination of synthetic beta-carotene and synthetic Vitamin E.
·The follow-up periods for the 19 studies were often short, averaging from 1.4 to 8.2 years. In many cases the chronic diseases suffered by study participants would not be able to be significantly impacted over shorter time periods.
A number of additional limitations have been cited by the authors of the study.
Misinterpretations of the study
The principles of study selection and analysis used by the Johns Hopkins team are on the whole reasonable and can be justified scientifically, albeit with an acceptance of the study’s limitations.
The biggest issues affecting consumer choice and governmental regulation are related to study interpretation, both by the authors and others subsequently.
Vitamin E meta-analysis misleads consumers