A US study linking consumption of vitamin E supplements with cancer demonstrates nothing more than the dangers of smoking, experts say.
Researchers analysing incidences of lung cancer and supplement consumption in a cohort of 78,000 people aged 50-76 from Washington State said evidence indicated long term intake of the vitamin resulted in a "small increased risk" of contracting the disease.
The study, published in the American Journal of Respiratory and Critical Care Medicine, found that over the course of a decade there was a 5% increased risk of developing lung cancer for every 100mg of vitamin E supplement taken daily.
Dr Christopher Slatore of the University of Washington in Seattle, who led the study, told the BBC: "Our results should prompt clinicians to counsel patients that these supplements are unlikely to reduce the risk of lung cancer and may be detrimental."
But one leading expert in vitamin E, Professor Maret Traber from Oregon State University, pointed out that in spite of the researchers' conclusion, the abstract from the study admitted: "The risk of supplemental vitamin E was largely confined to current smokers."
"It would seem the best strategy [for avoiding lung cancer] is to quit smoking," she said.
The Council for Responsible Nutrition said: "These results must be placed in the proper context. There is an unequivocal connection between smoking and increased lung cancer risk. Within this cohort, current smokers were 2,400% more likely to develop lung cancer. Contrast that with a trend toward a 5% increase in risk that the researchers observed with supplemental vitamin E — and this was mainly isolated to high vitamin E and mainly in current smokers. The headline associated with this study should simply be 'Smokers at risk.'"
There was actually a reduction in lung cancer risk observed with modest doses of vitamin E, said the CRN, but this was "clearly downplayed by the authors in favour of the ?bad news.'"
WH Leong, vice president of Vitamin E supplier Carotech, said it was important to take account of the form of vitamin E taken by subjects in the trial.
"Not all vitamin E is created equal," he said. "In this particular study 90% of the vital cohort used dl-alpha tocopheryl acetate, the synthetic form of vitamin E as opposed to the other, naturally occurring seven forms of vitamin E."
Studies had shown these natural forms of vitamin E to have greater health benefits than alpha tocopheryl, he said, adding: "To lump all forms of vitamin E together by using the term 'vitamin E' is a great disservice to the industry and, most importantly, outright misleading."
The researchers also looked for a link between lung cancer and consumption of multi-vitamins, vitamin C and folic acid supplements — but none was found.