Vitamins get F’ in cancer prevention
Published: Tuesday, January 6, 2009 at 4:32 p.m.
Last Modified: Tuesday, January 6, 2009 at 4:36 p.m.
A flotilla of recent studies – including two papers published Wednesday – has sunk the notion that individual vitamin supplements prevent cancer.
With so many earlier studies suggesting that people can eat their way to longer lives, experts acknowledge that their latest findings may leave people confused and even frustrated.
“A lot of people are looking at this and asking, ‘What happened?’ “ says Lori Minasian, whose study in Wednesday’s Journal of the American Medical Association found that taking vitamin E or selenium does not ward off cancer.
But researchers also say that diet is one of the most difficult areas to study.
Unlike lab rats, after all, no one eats one thing all the time.
“Cancer is complex and the interaction of nutrients is complex, so put the two together and you’ve got a lot of really tough scientific questions to answer,” says the American Cancer Society’s Colleen Doyle.
Researchers have noted for years that populations with healthy diets – lots of vegetables, little junk food – are less likely than others to get cancer, says Peter Gann of the University of Illinois-Chicago, who wrote an editorial accompanying the new papers.
It’s been much more challenging to tease out the specific foods – or even compounds – that keep cells from turning malignant, Gann says. Is it the fish oil? The soy? The lack of red meat?
Experts also note that the specific dose of a vitamin may be critical.
People who get too little of a nutrient may be at greater risk of cancer, but so may those who get too much, Minasian says. Given the popularity of vitamins and other supplements, she says it’s important for researchers to find the right combination.
Other experts, such as Gann, say that it may be time for researchers to abandon the idea of using individual vitamins to prevent cancer.
Instead, he says, health-conscious consumers should focus on getting their vitamins from plant foods, such as vegetables and whole grains, which contain precise mixtures of hundreds or even thousands of compounds. Many of these compounds may work better in the combinations selected by nature.
Doyle says there are still lots of proven ways, in addition to a plant-based diet, to reduce the risk of cancer: Exercise, maintain a healthy weight and avoid tobacco. Screenings for colon cancer, cervical cancer and breast cancer also have been shown to save lives.
Yet in spite of several decades of nutrition research, Gann says, doctors haven’t yet found an exact prescription for the perfect anti-cancer diet.
“I wouldn’t want to give anyone the impression that you just need to eat five servings a day and limit meat,” Gann says. “It may turn out that you need to do much more. It’s not clear how much dietary modification people have to make to see any benefit.”
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