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Dietary supplements ‘increase mortality’ in older women

Some dietary supplements - including mulitvitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper - are associated with increased total mortality risk in older women, while calcium is associated with a decreased risk, a study finds.

A total of 38,772 women who participated in the Iowa Women's Health Study were investigated - the mean age was 61.6 years at baseline in 1986.  By the end of the study period in 2008, 15,594 participants had died.

Researchers examined data on supplement use from self-report questionnaires completed in 1986, 1997 and 2004, and found supplemental iron was most strongly associated with increased mortality (hazard ratio 1.10). 

Multivitamins (1.06), vitamin B6 (1.10), folic acid (1.15), magnesium (1.08), zinc (1.08) and copper (1.45) were also associated with increased mortality, compared with non-use. But use of calcium had a hazard ratio of 0.91.

Study leader Dr Lisa Harnack, associate professor of epidemiology at the university of Minnesota, said:‘Among the elderly, use of supplements is widespread, often with the intention of attaining health benefits by preventing chronic diseases. Our study raises concerns regarding their long-term safety.'

Arch Intern Med 2011, online 10 October