Campaigners and industry groups have questioned the validity of a study by scientists in Finland linking vitamin use with a higher death rates among older women.
The study, carried out by the University of Eastern Finland, was based on self-reported interviews completed by 38,000 US women in their 50s and 60s.
The team concluded that multivitamins, folic acid, vitamin B6, magnesium, zinc, copper and iron in particular appear to increase mortality risk.
However they acknowledge that the usefulness of their findings relied on how well the women had been able to recollect their supplement use over two decades.
Even so, Dr Jaakko Mursu, who led the Finnish team, concluded: “Based on existing evidence, we see little justification for the general and widespread use of dietary supplements”.
Other scientists used the report’s findings to challenge the increasing use of higher potency supplements.Drs Christian Gluud and Goran Bjelakovic, who review research for the Cochrane Database of Systematic Reviews to evaluate best evidence, told the BBC: “We think the paradigm ‘The more the better’ is wrong. We believe that for all micronutrients, risks are associated with insufficient and too-large intake.”
But natural health campaigners and industry groups have challenged the report’s findings which they say exclude consideration of key factors that could influence mortality rates, including pharmaceutical drug use, pre-existing disease and the form of vitamin and mineral taken.
Dr Robert Verkerk, technical director at Alliance for Natural Health International (ANH-Intl) said: “Our view is that the self-reporting questionnaires, and lack of any supporting data on nutrient status of the study’s subjects, means that the majority of the trends emerging from the adjusted data on which the study’s conclusions were based are likely to be anomalous.”
Verkerk added that that the way the researchers had presented their findings “played into the hands of the pharmaceutical industry, the single biggest contributor to, and controller of, medical research”.
Leading US nutritionist and Natural Products contributor, Jack Challem, said: “The only really significant association (in the report’s findings) was between iron supplements and a greater risk of death, which has been known for years. What the researchers and editors seemed to miss is that older women (or men) have a greater risk of death simply because of their age, their greater likelihood of having serious diseases, and their use of multiple drugs, a common cause of illness (from side effects) and of death. For all we know, the risk of death might just as well have been associated with the use of the internet or cell phones. These reports made for great headlines, but very poor science.”