Vitamins and Mortality: An Interview With Jaakko Mursu

Linda Brookes, MSc; Jaakko Mursu, PhD

Disclosures

January 24, 2012

In This Article

Background to the Interview

A recently published analysis of data from the Iowa Women's Health Study by Dr. Mursu and his colleagues concluded that in older women, several commonly used dietary vitamin and mineral supplements, including multivitamins, folic acid, iron, and copper, may be associated with increased total mortality risk.[1] They also found that, in contrast to the findings of many previous studies, calcium was associated with decreased risk.

Previously, researchers in the same group showed that the use of dietary supplements in the United States had increased markedly between 1986 and 2004.[2] The long-term health consequences of many of these supplements remained unknown. On the basis of the previous studies, researchers hypothesized that use of dietary supplements is not associated with a reduced rate of total mortality.

In a study supported by the National Cancer Institute, the Academy of Finland, the Finnish Cultural Foundation, and the Fulbright program, Dr. Mursu and his colleagues examined the association between vitamin and mineral supplements and mortality rate among 38,772 older women (99% white, average age 61.6 years) who provided information about diet and supplement use in 1986, 1997, and 2004 via questionnaires. Self-reported supplement use increased substantially between 1986 and 2004, with 62.7% of women reporting use of at least 1 supplement daily in 1986, 75.1% in 1997, and 85.1% in 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.

Dr. Mursu’s group found that, consistent with their original hypothesis, the use of most dietary supplements was not associated with a reduced rate of total mortality. In contrast, in this multivariable-adjusted analysis, many supplements were associated with increased risk for total mortality compared with corresponding nonuse:

  • multivitamins (hazard ratio [HR], 1.06 [95% confidence interval [CI], 1.02-1.10]; absolute risk increase [ARI], 2.4%)

  • vitamin B6 (HR, 1.10 [95% CI, 1.01-1.21]; ARI, 4.1%)

  • folic acid (HR,1.15 [95% CI, 1.00-1.32]; ARI, 5.9%)

  • iron (HR,1.10 [95% CI, 1.03-1.17]; ARI, 3.9%)

  • magnesium (HR,1.08 [95% CI, 1.01-1.15]; ARI, 3.6%)

  • zinc (HR,1.08 [95% CI, 1.01-1.15]; ARI, 3.0%)

  • copper (HR,1.45 [95% CI, 1.20-1.75]; ARI, 18.0%)

Of note, use of calcium was consistently inversely related to total mortality rate (HR, 0.91 [95% CI, 0.88-0.94]; absolute risk reduction, 3.8%), in contrast to the findings of previous studies.[3,4,5] The findings for iron and calcium were replicated in separate analyses across shorter follow-up intervals (10, 6, and 4 years) starting in 1986, 1997, and 2004; during each interval, approximately 15% of the original participants died. A dose-response relationship was seen for supplemental iron, with significantly increased risk for mortality at progressively lower doses as women aged throughout the study. There was no dose-response relationship for calcium.

The researchers acknowledged that their findings did not exclude the possibility of benefits of supplements, such as improved quality of life, but they concluded that the study raised concern about their long-term safety. "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," they concluded

In an invited commentary published with the study,[6] Goran Bjelakovic, MD, DMSc (University of Nis, Nis, Serbia), and Christian Gluud, MD, DMSc (Copenhagen University Hospital, Denmark), noted that its findings added to "the growing evidence demonstrating that certain antioxidant supplements, such as vitamin E, vitamin A, and beta-carotene, can be harmful," while highlighting the difference in the result with respect to calcium, "which may require further study." They also concluded that "We cannot recommend the use of vitamin and mineral supplements as a preventive measure, at least not in a well-nourished population," adding, "Those supplements do not replace or add to the benefits of eating fruits and vegetables and may cause unwanted health consequences."

Dr. Mursu spoke with Linda Brookes, MSc, for Medscape Cardiology, to discuss the implications of the study results for Medscape readers.

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