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Friday, April 18, 2008

Recent Bad Press About Nutritional Supplements...


If you are one of my clients, you will know that I often recommend nutritional supplements as part of a nutritional therapy programme. I have used them with myself and clients for years and I think they are extremely useful, safe and effective.

Recently we have been confronted with headlines such as 'Vitamin Supplements May Increase Mortality'. This kind of headline is designed solely to sell newspapers, and fortunately the science behind it is unsound and misleading.

Here is an excerpt from a newsletter I have just been sent, regarding this recent review:


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The "study" was led by Serbian scientist and "visiting researcher" at Copenhagen University Hospital, Goran Bjelakovic, whose name is now synonymous with vitamin meta-analyses (studies of other studies) which appear to show that vitamin supplements either don't work or end up increasing your risk of death.

The Danish researchers reviewed 67 trials dating back to 1977 in which the effect of antioxidants were analysed, and have come to the conclusion that beta carotene, vitamin A and vitamin E may increase mortality. The strangest thing about this review is that the relative mortality risk, which forms the basis of the claims that vitamins decrease life expectancy, is calculated using information from studies which sometimes quote the exact opposite. For example, the trial with the highest increased mortality risk of 3.3% (1 patient in a study of 12) was conducted by Prince et al(1) who clearly concluded that “one patient died from unrelated causes during active treatment”.

Another trial which the review claims found an increased mortality rate was by Chylak et al(2). A closer inspection reveals that what the researchers actually recorded was that “twelve patients died during the course of the five year trial. Fishers exact test did not reach significance for the difference between treatment groups”. They even go on to say that “there were no serious safety issues during the trial”.

Mooney et al(3), while having one of the highest mortality risk increases according to the Danish reviewers, actually records a section in the full report entitled “Adverse events” which goes on to clarify that “one participant died from a myocardial infarct and 2 cancers were identified during the study. It is unlikely that these events were associated with vitamin supplementations due to the short exposure before diagnosis and the long latency of cancer”. Not only that - this trial actually found that taking vitamins E and C could significantly reduce the levels of carcinogenic polycyclic aromatic hydrocarbons that are elevated in smokers, “suggesting that antioxidant supplementation may mitigate some of the procarcinogenic effects of exposure”.

If you look a little further into the full text of a study by Manuel-y-Keenoy et al(4), which has been recorded by the reviewers as resulting in a 3% increase in mortality risk, you can see that nowhere in the study does it state that anyone even died. It does record that “during the course of the study one patient from each group dropped out, one due to thyroid dysfunction and one due to an accident. These two patients are not included in the statistical analysis”.

While being used by the Danish researchers as further evidence of the danger of antioxidants, what Salonen et al (5) actually say in their study is that “Both the vitamin E and C were safe. There were neither excess deaths nor excess of other adverse events in the groups randomised to supplements”. It is interesting just to note that the authors of this trial concluded that “this randomised clinical trial shows that long term supplementation of hypercholesterolemic persons with reasonable doses of both vitamin E and slow- release vitamin C combined can retard the progression of common carotid atherosclerosis, especially in men”.


References

(1.) Prince MI, Mitchison HC, Ashley D, et al. Oral antioxidant supplementation for fatigue associated with primary biliary cirrhosis: results of a multicentre, randomised, placebo-controlled, cross-over trial. Aliment Pharmacol Ther. 2003;17:137-143

(2.) Chylak LT Jr, Brown NP, Bron A, et al. The Roche European American Cataract Trial (REACT): a randomised clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract. Ophthalmic Epidemiol. 2002;9:49-80
(3.) Mooney LA, Madsen AM, Tang D, et al. Antioxidant vitamin supplementation reduces benzo(a)pyrene-DNA adducts and potential cancer risk in female smokers. Cancer Epidemiol BioMarkers Prev. 2005;14:237-242

(4.) Manuel-y-Keenoy B, Vinckx M, Vertommen J, Van Gaal L, De Leeuw I. Impact of vitamin E supplementation on lipoprotein peroxidation and composition in type I diabetic patients treated with atorvasstatin. Atherosclerosis. 2004;175:369-376

(5.) Salonen RM, Nyyssonen K, Kaikkonen J, et al. Antioxidant supplmentation in atherosclerosis prevention study:six year effect of combined vitamin A and E supplementation on therosclerotic progression: the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) Study. Circulation. 2003;107:947-953


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This information was provided Nutri. If you have any questions about the use of nutritional supplements, please do not hesitate to contact me.









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