(NaturalNews) A German professor has questioned the findings of a recent study that linked beta-carotene supplements to an increased risk of lung cancer in smokers.
"The obvious weakness of this study lies in its methodology," said Hans Konrad Biesalski of the Institute for Biological Chemistry and Nutrition at the University of Hohenheim.
The study, conducted by researchers from the University of North Carolina (UNC)-Chapel Hill published in March in the
American Journal of Epidemiology, found that smokers who took
beta-carotene, lutein or retinol
supplements over the long term had a significantly higher risk of
lung cancer than those who did not take the supplements. The risk of lung
cancer increased relative to the amount of time that supplements were taken.
Biesalski criticized the study for relying on dietary questionnaires to assess participants'
supplement intake.
"For this study, participants were asked to give details from memory of food supplements which they had taken in some cases 10 years ago," he said. "It is hardly conceivable that the subjects were able to remember accurately enough in which sequence, how frequently and in what composition they had taken products containing
micronutrients in the previous four or ten years. ... The validity of the questionnaires used and above all the conclusions drawn from them are therefore questionable."
Biesalski attributes some of the study's more perplexing findings to this methodological flaw.
"For the first time [the study showed] that it is not the absolute dose that increases the
risk of lung cancer, but the length of time of use," he said. "This is not surprising, since recall of dosages is surely even more dubious than recall of preparations."
He noted that dietary supplements can play an important role in cancer prevention, although they cannot in themselves make up for poor lifestyle choices.
"Numerous epidemiological studies confirm a preventive effect for lung cancer from a balanced, carotenoid and vitamin rich
diet," Biesalski said. "Clearly, however, micronutrients alone cannot compensate the consequences of harmful behavior such as smoking."
Sources for this story include:
www.nutraingredients.com.
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