Dietary Supplements and Mortality Rate in Older Women

The Iowa Women’s Health Study

Jaakko Mursu, PhD; Kim Robien, PhD; Lisa J. Harnack, DrPH, MPH; Kyong Park, PhD; David R. Jacobs Jr, PhD

Arch Intern Med. 2011;171(18):1625-1633. doi:10.1001/archinternmed.2011.445

Background  Although dietary supplements are commonly taken to prevent chronic disease, the long-term health consequences of many compounds are unknown.

Methods  We assessed the use of vitamin and mineral supplements in relation to total mortality in 38 772 older women in the Iowa Women’s Health Study; mean age was 61.6 years at baseline in 1986. Supplement use was self-reported in 1986, 1997, and 2004. Through December 31, 2008, a total of 15 594 deaths (40.2%) were identified through the State Health Registry of Iowa and the National Death Index.

Results  In multivariable adjusted proportional hazards regression models, the use of multivitamins (hazard ratio, 1.06; 95% CI, 1.02-1.10; absolute risk increase, 2.4%), vitamin B6 (1.10; 1.01-1.21; 4.1%), folic acid (1.15; 1.00-1.32; 5.9%), iron (1.10; 1.03-1.17; 3.9%), magnesium (1.08; 1.01-1.15; 3.6%), zinc (1.08; 1.01-1.15; 3.0%), and copper (1.45; 1.20-1.75; 18.0%) were associated with increased risk of total mortality when compared with corresponding nonuse. Use of calcium was inversely related (hazard ratio, 0.91; 95% confidence interval, 0.88-0.94; absolute risk reduction, 3.8%). Findings for iron and calcium were replicated in separate, shorter-term analyses (10-year, 6-year, and 4-year follow-up), each with approximately 15% of the original participants having died, starting in 1986, 1997, and 2004.

Conclusions  In older women, several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk; this association is strongest with supplemental iron. In contrast to the findings of many studies, calcium is associated with decreased risk.

 

Author Affiliations: Department of Health Sciences, Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio Campus, Kuopio, Finland (Dr Mursu); Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis (Drs Mursu, Robien, Harnack, and Jacobs); Department of Food and Nutrition, Yeungnam University, Gyeongbuk, Republic of Korea (Dr Park); and Department of Nutrition, School of Medicine, University of Oslo, Oslo, Norway (Dr Jacobs).

Summary by Dr.Rehan: 

Supplement with vitamins and minerals only if you need to. Otherwise, healthy people should focus primarily on a whole-foods diet with fruits and vegetables. The effects of long-term supplementation with vitamins may cause unwanted health consequences.