Another study shows a powerful association between taking multiple vitamin supplements (MVM) and better health. The largest study ever conducted of multiple vitamin use in postmenopausal women with breast cancer found a strong linkage between MVM use and better prognosis.
The Women’s Health Initiative is a massive study (over 161,000 American women) providing us insight into a broad range of lifestyle factors, health and diseases. Whenever you learn of some major discovery on women’s health, the odds are high that WHI data are the source of the groundbreaking research.
Investigators studied the 7728 women in the WHI who were diagnosed with invasive breast cancer and followed them for over seven years. About 38% of the women diagnosed with invasive breast cancer were taking an MVM. Those women were 30% less likely to die of their invasive breast cancer than the women who were not taking an MVM.
Studies like this are always open to question because association does not prove causation. What are the uncertainties in this study?
Women who take an MVM often have other good health habits. Could those other habits explain their improved chances against their cancers? Investigators worked diligently to exclude these sources of confusion. They analyzed the data, digging out the protective effects of age at time of diagnosis, alcohol use, depression, diabetes, education level, hormone characteristics of the tumor, physical activity, race/ethnicity, self report of health status, smoking status and weight. Even after carving out all of these confounders, nearly every known risk factor for breast cancer, the beneficial association with MVM use held up.
Women in this study had started taking MVM supplements before they developed breast cancer. Only postmenopausal women were studied. MVM supplements might not help women who start taking MVMs after they are diagnosed or premenopausal women. Of course, MVMs might help those women even more. We do not know yet.
Even IF there is some unidentified protective factor more common among women using MVMs, the impact is so big (30% reduction in deaths), that it appears very unlikely to disappear. This is another excellent reason to take an MVM, especially a good one.