New data from a huge study in the U.S. suggests that multivitamins do little to lower rates of common cancers or heart disease in older women.
The study of 161,808 postmenopausal women echoes recent disappointing vitamin studies in men. But even the authors note the research doesn't necessarily mean multivitamins are useless.
For one thing, the data came from an observational study, not a controlled experiment, and researchers could only ask the study subjects to report on their multivitamin use.
Also, the study was only eight years long, so it's not clear if taking vitamins might help prevent cancers that take many years to develop, notes the study's lead author, Marian Neuhouser of the Fred Hutchinson Cancer Research Center in Seattle.
The study, published this week in Archives of Internal Medicine, analyzed data on women in their 50s and up who participated in a long-running government study on postmenopausal women, called the Women's Health Initiative (WHI).
Almost 42 per cent of the women said they used multivitamins regularly. The researchers found that after about eight years, there were roughly equal numbers of cancers, heart attacks and other cardiovascular problems in both the vitamin users and nonusers.
The vitamin users and nonusers also died at similar rates.
The only difference the researchers did observe was lower rates of heart attacks among users of "stress formula" vitamins. Many stress supplements include high doses of folic acid and other B vitamins - which studies have suggested may help in the prevention of cardiovascular disease.
The authors note billions of dollars are spent on multivitamins every year, with many users believing the pills will prevent chronic diseases.
"These results suggest that multivitamin use does not confer meaningful benefit or harm in relation to cancer or cardiovascular disease risk in postmenopausal women," the authors conclude.
While the study suggests that multivitamins don't seem to prevent heart disease and cancer, many studies have found that diets full of vitamin-rich foods do, the authors point out.
"Nutritional efforts should remain a principal focus of chronic disease prevention," they write, "but without definitive results from a randomized controlled trial, multivitamin supplements will not likely play a major role in such prevention efforts."
