According to background information in the article, the consumption of dietary supplements in the U.S. has substantially increased over the last 10 years.
The authors comment:
"At the population level, dietary supplements contributed substantially to the total intake of several nutrients, particularly in elderly individuals."
Jaakko Mursu, Ph.D., of the University of Eastern Finland, Kuopio, Finland, and the University of Minnesota, Minneapolis, and teams conducted a study to examine the link between vitamin and mineral supplements and the mortality rate in older women. Their study was based on data from the Iowa Women's Health Study in which a total of 38,772 women with an average age of 61.6 years self-reported their supplement use during 1986, 1997 and 2004 in a questionnaire.
15,594 women, i.e. 40.2% of all 38,772 participants who did the first survey in 1986 died over an average follow-up time of 19 years. According to the questionnaires, the consumption of supplements increased significantly between 1986 and 2004. Figures rose from 62.7% of women using at least one daily supplement in 1986 to 75.1% in 1997 and 85.1% in 2004 respectively.
The findings revealed that although most supplements were not linked to reduced total mortality in older women, numerous supplements nevertheless seemed to increase the linked mortality risk.
The researchers carried out adjustments and discovered that using multivitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper, were all linked to an increased risk of death in the study population, with the exception of calcium supplements, which appeared to reduce risk of mortality. Iron supplements demonstrated the highest link between supplement intake and mortality risk.
The authors noted that as the women aged throughout the study their response to iron dosages progressively increased the risk of mortality.
Researchers replicated the results for both iron and calcium supplements in a separate, short-term analyses with a follow-up at four, six and 10 years.
They conclude saying:
"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."
Accompanying CommentaryGoran Bjelakovic, M.D., D.M.Sc., of the University of Nis in Nis, Serbia, and Christian Gluud, M.D., D.M.Sc., of Copenhagen University Hospital in Copenhagen, Denmark, discussed the study's findings in an invited comment stating that Mursu and his team:
". . . . add to the growing evidence demonstrating that certain antioxidant supplements, such as vitamin E, vitamin A, and beta-carotene, can be harmful.
Dietary supplementation has shifted from preventing deficiency to trying to promote wellness and prevent disease. Until recently, the available data regarding the adverse effects of dietary supplements has been limited and grossly underreported. We think the paradigm 'the more the better' is wrong. One should consider the likely U-shaped relationship between micronutrient status and health.
"We cannot recommend the use of vitamin and mineral supplements as a preventive measure, at least not in a well-nourished population. Older women (and perhaps men) may benefit from intake of vitamin D3 supplements, especially if they have insufficient vitamin D supply from the sun and from their diet. The issue of whether to use calcium supplements may require further study."
Written by Petra Rattue