17 novembre 2008

Vitamins do not reduce cancer risk, says study

James Randerson, science correspondent (The Guardian)

Taking vitamin A and E supplements does not lower your risk of cancer, according to the results of a large clinical trial involving nearly 15,000 men in the US.

Both vitamins are powerful antioxidants - substances that can tackle harmful byproducts of the body's metabolism which can cause DNA damage and hence trigger cancer. However, the study shows that taking the vitamins in supplement form has no effect at all on cancer.

"There have been a number of previous studies that have suggested that vitamin E and vitamin C might be important in the prevention of cancer," said Dr Howard Sesso, an epidemiologist at Brigham and Women's hospital in Boston, Massachusetts. These were mostly small lab studies or research on animals. But a 1998 study of men in Finland suggested that vitamin E supplements reduced prostate cancer cases by 32% and deaths by 41%.

"The lack of an effect that we observe for vitamin E or C on cancer does convince us that these particular doses that we tested really have no role for recommendation for cancer prevention," said Sesso.

His team recruited 14,641 male doctors and assigned them to four groups which took a different combination of the supplements or their placebos. The team looked at the number of deaths from cancer and found no statistical differences.

Sesso reported the results of the Physicians Health Study II trial at the American Association for Cancer Research's meeting in Prince George's county, Maryland.

Ed Yong, health information manager at Cancer Research UK, said there was growing evidence vitamin supplements did not prevent the risk of cancer. He said having a healthy diet was more important.

Voilà qui déplaira aux adeptes des théories de Linus Pauling, qui prétendait que des mégadoses de vitamine C permettait de lutter contre le cancer. Ces théories ont influencées des générations de parents éblouis par l'autorité du Prix Nobel de Chimie dans un domaine où il n'avait pas d'expertise. Il n'existe plus grand monde pour soutenir ces théories aujourd'hui, sauf les adeptes de la pseudo-médecine "orthomoléculaire", tels Matthias Rath et son lucratif business de cocktails vitaminés pour malades du tiers-monde.