A study by scientists in the United States has found that the long-term use of multivitamins have no impact on a postmenopausal woman's risk of cancer or heart disease.
The researchers from the Fred Hutchinson Cancer Research Center in Seattle say the $20 billion spent on dietary supplements has little scientific data to support their use.
The team conducted the largest study of its kind into long-term multivitamin use and found they had no impact on the risk of common cancers, cardiovascular disease or overall mortality in postmenopausal women.
The study, a part of the Women's Health Initiative study, focused on the effects of multivitamins because they are the most commonly used supplement, but lead author Dr. Marian L. Neuhouser, an associate member of the Public Health Sciences Division at the Hutchinson Center, says to their surprise it was found that multivitamins did not lower the risk of the most common cancers and also had no impact on heart disease.
The study involved almost 162,000 women enrolled in the Women's Health Initiative, one of the largest U.S. prevention studies of its kind designed to address the most common causes of death, disability and impaired quality of life in postmenopausal women.
The women were followed for about eight years and the research revealed that 41.5% of the study participants used multivitamins on a regular basis and these women were more likely to be white, live in the western United States, have a lower body-mass index - they were also more physically active and had a college degree or higher as compared to non-users - they were also more likely to drink alcohol but less likely to smoke and also ate more fruits and vegetables and consumed less fat than non-users.
During the eight-year study period, 9,619 cases of breast, colorectal, endometrial, renal, bladder, stomach, lung or ovarian cancer were reported, as well as 8,751 cardiovascular events and 9,865 deaths and the researchers found no significant differences in risk of cancer, heart disease or death between the multivitamin users and non-users.
Dr Neuhouser says these findings are consistent with most previously published results regarding the lack of health benefits of multivitamins but this study provides definitive evidence as the 'Women's Health Initiative' is one of the largest studies ever done on diet and health - because the study had such a large and diverse sample size, including women from 40 sites across the nation, Dr. Neuhouser says the results can be generalized to a healthy population.
Dr. Neuhouser and her colleagues advise women who want to make sure they're getting optimal nutrition to get their nutrients from food - she says whole foods are better than dietary supplements and getting a wide variety of fruits, vegetables and whole grains is particularly important.
The research is published in the February 9th issue of the Archives of Internal Medicine and was funded by the National Heart, Lung and Blood Institute, National Institutes of Health and U.S. Department of Health and Human Services; it involved researchers from the Albert Einstein College of Medicine, the Department of Nutritional Sciences at the University of Arizona, Harvard Medical School, Northwestern University, University of Alabama, and Medstar Research Institute.