Are antioxidants harmful? Many subscribers may have been concerned by misleading newspaper headlines suggesting harmful effects from taking anti-oxidant supplements. These were based on a meta-analysis study published in the Journal of the American Medical Association (JAMA) entitled "Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention, Systematic Review and Meta-Analysis". The study in question is a meta-analysis, which is NOT new clinical research. This type of study analyses data from existing studies in a given field, and therefore represents nothing more than a new interpretation of existing data. Reputable supplement company Solgar www.solgar.co.uk asked Dr Richard Passwater, one of the world's leading experts on antioxidant research, to comment on the JAMA article. His response included the following points: - This is not a clinical study, but a review of certain SELECTED previous studies. Such studies are only as good as the trials selected and this trial has worse inclusion criteria than the Miller meta-analysis of a couple of years ago that was eventually discredited.
- In the past we have found that reasons have been dreamed up for excluding cases where benefit was found from such negative–finding meta analyses. The vitamin E meta-analysis of two years ago is an example.
- The trials selected appear to be mostly 'secondary events' where someone, for instance, had a heart attack and was then entered into a short-term trial. They tend not to be a measure of prevention (of the first heart attack etc), nor are they long-term – it takes two years for the preventative effects of vitamin E to manifest itself - nor are they high-dose.
- This meta-analysis purports to be a study of long-term supplementation, yet includes a study on vitamin A of a one-time, single-dose of 200,000IU.
- The one key point of a valid meta-analysis is to compare and combine studies that are extremely similar. This meta-analysis combines studies that are extremely dis-similar, e.g. the one-day vitamin A study combined with data from studies lasting years.
- The conclusion seems so out of context with the body of science that it is suspect. A meta-analysis carries little scientific weight, whereas some of the studies that do show preventive and life-extending effect are better studies; i.e. not a meta-analysis, but clinical data.
This poorly designed meta-analysis does not undo the overwhelming majority of studies showing the safety and effectiveness of antioxidant supplements that have withstood the test of time. It does not change the basic facts that antioxidants are safe and effective, so healthy consumers can feel confident that they can still safely take their antioxidant supplements. What do nutritionists believe about antioxidants? Leading nutritionist Patrick Holford www.patrickholford.com suspects the study is an attempt to demote vitamin therapy so we all keep on taking drugs. Four reasons that, in his opinion, discredit this meta-analysis are: - One way to evaluate a meta-analysis is to examine how trials are included and excluded. A study in which 87,200 nurses were given 67mg of vitamin E daily for more than two years showed a 40% drop in fatal and non-fatal heart-attacks compared to those not taking the vitamin E supplement. In another study, 39,000 male health professionals were given 67mg of vitamin E for the same time and achieved a 39% reduction in heart attacks. Neither of these studies is included.
- Patrick Holford disagrees with the way bias is handled. For instance, it is well known that taking statin drugs, that lower cholesterol and induce CoQ10 deficiency, makes vitamin E harmful by turning it into an oxidant. This is an obvious bias that is not even mentioned. Once these trials are excluded, vitamin E has an overall positive effect.
- Another check is to see if the most negative studies are actually negative, as these can skew results overall. One included study purported to show an increased risk of gastrointestinal cancer. Patrick Holford contacted Dr Pelayo Carrera, the author of this cancer study, to ask about the increased risk supposedly found. Dr Carrera was amazed because his research had found a clear benefit from taking vitamins, and it did not study mortality. Without this study the conclusion of the meta-analysis that antioxidants may increase gastro-intestinal cancer becomes completely invalid.
- The conclusion of the meta-analysis says "Treatment with beta-carotene, vitamin A and vitamin E may increase mortality". What it fails to say, which is clearly shown in the results, is that "vitamin C given singly or in combination with other antioxidants, and selenium given singly or in combination with other antioxidant supplements may reduce mortality". It also fails to say that "beta-carotene or vitamin A did not show increase in mortality if given in combination with other antioxidants", or that "vitamin E given singly or combined with 4 other antioxidants did not significantly influence mortality".
The one take-home message is that antioxidants are team-players and reduce mortality in combination, and that vitamin C and selenium are more beneficial than beta-carotene or vitamin A. Acknowledgements Thanks for the use of this material are due to supplement company Solgar www.solgar.co.uk - advancing Wellness since 1947. Also to Patrick Holford, co-author of "Food is Better Medicine than Drugs" – see www.foodismedicine.co.uk for his in-depth feature on the antioxidant myth. Remember, if you need more motivation on a healthy life-style, I offer Health Coaching sessions. Click for health coaching website. Please feel free to send this information/newsletter to anyone who may find it interesting, or who may like to subscribe. I promise your details will NEVER be rented or sold on and you will normally only be contacted once a month, but to be removed from this list, just click on the Subscription Management link below. With very best wishes, Joy Healey Eat Your Way to Better Health | |
|
