The large study was the latest to indicate that various vitamin supplements do not prevent common chronic diseases even as consumers spend billions of dollars on these popular products that line supermarket and drug store shelves.
"Essentially, there is no effect. And with such a large and diverse sample size, this is a pretty definitive statement that they are not harming anybody but they are not benefiting them either in terms of certain chronic disease risks," Marian Neuhouser of the Fred Hutchinson Cancer Research Center in Seattle said in a telephone interview.
Her team's study of 162,000 women, published in the Archives of Internal Medicine, was the largest of its kind to assess the value of taking multivitamins, although it involved no men.
The researchers followed the women, all past menopause, for eight years. About 42 percent took vitamins daily.
All the women had basically identical rates of breast, colorectal, lung, ovarian and other types of cancer, cardiovascular disease such as heart attack and stroke, and death from all causes, they found.
The researchers noted that Americans spend more than $20 billion annually on dietary supplements, a third of it on multivitamins. Many people take vitamin and mineral supplements to guard against chronic diseases or ward off a colds or flu.
Neuhouser advised consumers to eat a proper diet with enough fruit and vegetables to get proper nutrition.
"If people think that they're getting all of their essential nutrients through a vitamin pill, it just isn't true. There's nothing better than the actual foods," she said.
Andrew Shao of the Council for Responsible Nutrition, a dietary supplement industry group, said regardless of this study a majority of people could benefit from a multivitamin because so many are not getting enough essential nutrients.
Shao said by e-mail: "Multivitamins, like all other dietary supplements, are meant to be used as part of an overall healthy lifestyle; they are not intended to be magic bullets that will assure the prevention of chronic diseases, like cancer."
Many companies make multivitamins including Bayer with its One A Day and Wyeth with Centrum vitamins.
In October the U.S. National Cancer Institute stopped a study of 35,000 men designed to see whether taking selenium and vitamin E supplements prevent prostate cancer after slightly more cases of prostate cancer appeared in men taking only vitamin E and slightly more cases of diabetes in men taking selenium.
In November, a study involving 14,641 male U.S. doctors found that taking vitamin E or vitamin C supplements did not cut their risk for cancer or cardiovascular disease.
Last Mod: 10 Şubat 2009, 15:50