Millions of women take daily multivitamins after menopause, in the hope of preventing chronic diseases including cancer or heart disease. Some previous studies had suggested a possible protective effect of multivitamin use. A large new study out of the Fred Hutchinson Cancer Research Center in Seattle, Washington shows that there is no protective effect of multivitamin use on the risk of or mortality from these diseases.
The massive study included over 68,000 post-menopausal women who were participants in the Women's Health Initiative clinical trials. The women were participating in clinical trials of hormone therapy, dietary modification, and calcium and vitamin D supplementation. All the women were followed for approximately 8 years, and they provided detailed information about multivitamin use at baseline and various follow-up time points. Disease outcomes were recorded throughout the study, in particular the following: cancers of the breast, colon/rectum, endometrium, kidney, bladder, stomach, ovary and lung; cardiovascular disease (heart attack, stroke, and embolism) and total mortality.
Approximately 41% of the women took multivitamins on a daily basis. Analysis of multivitamin use and disease outcome showed that there was no association between the use of multivitamins and the risk of cancer, nor was there any association with the risk of cardiovascular disease.
In terms of gender influence, a study in 2008 followed 15,000 men for ten years, and reported no association between taking vitamins E and C and cancer risk. Finally, in October of this year, a study of 35,000 men showed that high doses of vitamin E and selenium have no effect on the risk of prostate cancer.
Interestingly, these results have had little to no effect on vitamin sales or use. "I'm puzzled why the public in general ignores the results of well-done trials," said Dr. Eric Klein, national study coordinator for the prostate cancer trial and chairman of the Cleveland Clinic's Glickman Urological and Kidney Institute. "The public's belief in the benefits of vitamins and nutrients is not supported by the available scientific data."