In the past year or so there have been a number of well-publicised reports of 'New Research' which claim to show that various food supplements could be dangerous. A closer look at these studies reveals that there are no new experiments, only very biased and unscientific reworking of previous research - the so-called 'meta-analysis'. This is a well known method of getting an overview of the combined results of several similar pieces of research. It is, however, not a suitable tool for examining studies of many different types and widely diverse subjects. These recent meta-analyses have been widely criticised within the scientific community, for they exhibit both extreme bias and highly questionable statistical methods. Just to redress the balance, and put people's minds at rest, we are reprinting a few of the many rebuttals that have been totally ignored by the press who were so keen to capitalise on the more negative 'research'.

ANTIOXIDANTS INCREASE MORTALITY? - The Review is Farcical and Unscientific !

Antioxidants - Can they really be bad for you?

Yet more bad science was reported throughout the media this week, leading to widespread panic about the use of nutritional supplements. 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.

The Chosen Trials

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 hypercholesterolaemic 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'.

In Conclusion

Unfortunately bad news sells, and it would seem that both the scientists responsible for this review and the media, have decided to yet again scaremonger the general public. Once again those that take positive action to not only increase life expectancy but to improve life quality, are left questioning their decisions. I hope this short review helps avoid that.

(With acknowledgements to Patrick Holford)

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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