Blog | Wednesday, October 12, 2011

QD: News Every Day--Vitamins shouldn't be routine for older women

Vitamin and mineral supplements were associated with increased total mortality, according to a study that found a dose-dependent relationship with iron and suggested a need to study calcium more closely to identify if it has any benefits.

Vitamins by DB-2 via Flickr and a Creative Commons licenseResearchers applied results from 38,772 older women in the Iowa Women's Health Study, which used self-reported supplement use in 1986, 1997 and 2004. Through December 2008, a total of 15,594 deaths (40.2%) were identified through the State Health Registry of Iowa and the National Death Index. Results appeared in the Oct. 10 issue of Archives of Internal Medicine.

Self-reported use of dietary supplements increased substantially during the study's span. In 1986, 1997, and 2004, 62.7%, 75.1%, and 85.1% of the women, respectively, reported using at least one supplement daily. The most common were calcium, multivitamins, vitamin C, and vitamin E. The most common combinations were calcium and multivitamins; calcium, multivitamins, and vitamin C; and calcium and vitamin C.

Compared to nonusers, increased total mortality risks were recorded for multivitamins (hazard ratio [HR], 1.06; 95% confidence interval [CI], 1.02 to 1.10; absolute risk increase [ARI], 2.4%), vitamin B6 (HR, 1.10; 95% CI, 1.01 to 1.21; ARI 4.1%), folic acid (HR, 1.15; 95% CI, 1.00 to 1.32; ARI 5.9%), iron (HR, 1.10; 95% CI, 1.03 to 1.17; ARI 3.9%), magnesium (HR, 1.08; 95% CI, 1.01 to 1.15; ARI 3.6%), zinc (HR, 1.08; 95% CI, 1.01 to 1.15; ARI 3.0%) and copper (HR, 1.45; 95% CI, 1.20 to 1.75; ARI 18.0%). Calcium was inversely related (HR, 0.91; 95% CI, 0.88 to 0.94; ARI, 3.8%).

The authors wrote,"[C]umulative effects of widespread supplement use, together with food fortification, have raised concern regarding exceeding upper recommended levels and, thus, regarding long-term safety. It is not advisable to make a causal statement of excess risk based on these observational data; however, it is noteworthy that dietary supplements, unlike drugs, do not require rigorous RCT [randomized controlled trial] testing, and observational studies are often the best-available method for assessing the safety of long-term use. 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."

An editorial pointed out that a third of the population of wealthy countries takes vitamins thinking they'll lead to better health. The study "add[s] to the growing evidence demonstrating that certain antioxidant supplements, such as vitamin E, vitamin A, and beta-carotene, can be harmful. Their results also concur with the findings of recent observational studies. The belief that antioxidant supplements are beneficial seems likely to have resulted from a collective error. Perhaps oxidative stress is one of the keys to extension of our life span.

"Dietary supplementation has shifted from preventing deficiency to trying to promote wellness and prevent diseases. Consumers believe that vitamin and mineral supplements are safe and use them without the supervision of their physicians. 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 believe that for all micronutrients, risks are associated with insufficient and too-large intake. Low levels of intake increase the risk of deficiency. High levels of intake increase the risk of toxic effects and disease. Therefore, we believe that politicians and regulatory authorities should wake up to their responsibility to allow only safe products on the market."

The publication's editor also commented on the lack of regulation.

"This permissive approach has encouraged sales of more than $20 billion annually for dietary supplements. [The study authors] find that consumers are getting little value for this expenditure and that increased mortality is associated with most of the commonly used vitamins and mineral supplements, not to mention the opportunity costs. A better investment in health would be eating more fruits and vegetables, among other activities. Because commonly used vitamin and mineral supplements have no known benefit on mortality rate and have been shown to confer risk, this article has been given our 'Less Is More' designation."