Study Raises Concern over Dietary Supplements and Mortality Risk

Academic researchers from South Korea, Norway, Finland, and the United States have come to a nervy conclusion surrounding dietary supplement usage in nearly 40,000 older women: several common dietary supplements appear to increase mortality risk.

Published in the journal Archives of Internal Medicine, the research is based on rates of vitamin and mineral supplement use in 38,772 women (mean age of 61.6 years at baseline) who participated in the Iowa Women’s Health Study. Women were questioned in 1986 (baseline), 1997, and 2004. Deaths were recorded through December 31, 2008.

Use of several common dietary supplements was linked to increased mortality compared to nonuse, including multivitamins, vitamin B6, folic acid, iron, magnesium, and copper. Contrary to previous research, calcium was linked to a lower mortality risk, as were vitamins C, D, and E, and vitamin B complexes.

While most supplements were not linked to increased risk of death in the study, heightened risks with the common products mentioned above led the researchers to conclude that, “Based on existing evidence, we see little justification for the general and widespread use of dietary supplements. We recommend that they be used with strong medically based cause, such as symptomatic nutrient deficiency disease.”

Aside from several study limitations admitted by the researchers, critics point to that last statement as muddying the sentiment against dietary supplement use. Steve Mister, president and CEO of the Council for Responsible Nutrition (Washington, DC) explains:

…the authors advise that dietary supplements only be used ‘with strong medically-based cause, such as symptomatic nutrient deficiency…’ Given the high dosages of iron reportedly being used by the women in the study-iron is the supplement for which there was the strongest negative association-it is highly likely the participants were taking the high dosage of iron reported in the study under a physician’s care for an iron deficiency which may itself have resulted in a shortened lifespan. But the piece purports to warn against over-the-counter use of vitamins.

Health comparisons drawn between supplement users and nonusers at baseline further question avoiding supplements altogether, as supplement users on average showed lower rates of diabetes, high blood pressure, smoking, and lower body mass index.

Funding for the Archives of Internal Medicine study was provided by a grant from the National Cancer Institute, the Academy of Finland, and a Fulbright Program Research Grant.