Do micronutrient supplements increase mortality for older women?

A new US study suggests that supplements containing multiple micronutrients may be associated with an increased mortality for older women. Experts question the hypothesis.

In the observational study, data from 38,772 women with a mean age of 61.6 years where collected over an average of 19 years (1). Health status was checked and dietary supplementation was self-reported at 3 points in time. The study results showed that supplementation increased substantially over time, with 62.7% of women reporting use of at least one supplement daily in 1986, 75.1%in 1997 and 85.1% in 2004.

The researchers reported that the use of most supplements was not associated with reduced total mortality. However, many supplements including multivitamins, vitamin B6, folic acid, magnesium, zinc, copper and especially iron appeared to be associated with increased mortality. Conversely, calcium supplements appeared to reduce mortality. The researchers concluded that they could see little justification for the general and widespread use of dietary supplements. They recommend that supplementation be limited to strong medically based cause, such as symptomatic nutrient deficiency disease.

Experts criticized the lack of a control (placebo) group in the study, with 85% of the women reporting the use of dietary supplements. This puts into question the validity of the conclusions. In addition, the researchers did not report nutrient intake amounts. It is therefore unclear whether or not the women exceeded the upper limits (UL) for safe daily micronutrient intake. Moreover, the authors dismissed the fact that the self-reported use of supplements upon admission to the study was associated with lower total mortality among supplement users than among non-users. The nutritional experts settled the debate that nutrients are by no means drugs. Nutrients are essential to health and life, but they cannot prevent multifactor diseases or death alone.

1. Mursu J. et al. Dietary supplements and mortality rate in older women – The Iowa Women’s Health Study. Arch Intern Med. 2011; 171(18):1625-1633.