Although many people regularly take vitamins because they think they will prevent chronic diseases and prolong life, the long-term health consequences of many compounds are unknown.
A lot of interest in these supplements has arisen from a recent article in the Archives of Internal Medicine that suggests taking vitamins and other dietary supplements may not be as healthy a choice as many of us have thought.
The article reports on a study that followed over 38,000 elderly American women (average age 62) for 20 years. When the study started about 66% reported using dietary supplements; by the time the study ended, that figure had risen to 85%. The authors looked at the use of supplements in relation to all-cause mortality (all causes of death). The use of several individual vitamins and minerals was statistically associated with increased risk of all-cause mortality when compared to nonuse; but, when adjustment was made for factors that could lead to false results, only copper and multivitamins showed this association. On the other hand, taking calcium and vitamin D was associated with a decreased risk of all-cause mortality when compared to nonuse; this carried over after adjustment.
Other researchers are quick to caution about reading too much into the study. It shows an association, not necessarily a cause and effect. The women may have been taking the supplements for an underlying health condition that itself caused the deaths, not the supplements. The increases in death were small and may not be clinically meaningful. And other factors besides the supplements may have led to the results.
Another article in the same issue of the journal found that men who take high doses of vitamin E for several years have a slightly higher risk of prostate cancer.
The widespread use of supplements by Americans arose from trying to prevent disease and promote wellness. But in a well-nourished population, there is little probability that they are needed to treat vitamin deficiencies, and the articles confirm that they do not ward off death and may cause harm. A more prudent choice may be to eat a balanced, varied and healthy diet.