Q: What’s your opinion about a well-publicized Iowa study that links supplement use to increased risk of mortality?
A: The study you are referring to is “The Iowa Women’s Health Study.” Although the subjects were all women, there’s the assumption that the results might also apply to men. The media have jumped on this study with headlines suggesting that supplements are bad. Let’s take a closer look.
The Iowa study was the basis for the article “Dietary Supplements and Mortality Rate in Older Women,” published in the October 10, 2011, Archives of Internal Medicine. The data came from a variety of questionnaires administered in 1986, 1997 and 2004. This type of research is considered an observational study. Using methods such as questionnaires makes it easy to involve a lot of subjects—38,000 women in the Iowa study—but it also makes it difficult to determine direct causal relationships. For example, you might do an observational study comparing professional basketball players to Olympic gymnasts and come to the conclusion that playing basketball makes you tall and practicing gymnastics makes you short. That’s one of the issues with the Iowa study.
At the start 13.5 percent of the subjects who were using supplements were also taking hormone drugs, compared to 7.2 percent of the group who were not taking supplements. Hormone drugs may have significant negative effects on health; for example, the hormone-replacement drug Premarin, which was especially popular in the ’80s, has been linked to increased risk of breast cancer and stroke. Further, the women taking supplements also ate 90 more calories per day than those who did not take supplements—although in reality those who take supplements often mistakenly believe that they can get away with a poor diet.
As for specific supplements, consider that the multivitamin-and-mineral supplements the women took often included vitamin A and iron, which can have adverse effects if taken in large doses. In fact, in their paper the authors note that with the exception of several supplements—and they specifically named iron—they found that “most dietary supplements were unrelated to total mortality rate.”
That said, a German study on supplements that began in 1994 and followed 11,083 men and 12,860 women over an average of 11 years found that “supplementation of antioxidant vitamins might possibly reduce cancer and all-cause mortality” (see “Vitamin/Mineral Supplementation and Cancer, Cardiovascular, and All-Cause Mortality in a German Prospective Cohort” published online ahead of print in the European Journal of Nutrition, July 22, 2011).
What’s especially interesting about the Iowa study is that the average life expectancy for women in 2003 was 80 years, and 50 percent of the women in the study lived longer than that! What comes to mind is the old joke: “My dad took vitamins for over 100 years, and it didn’t do him any good!”
Although there is some information of value in this study, such as the risks of supplementing your diet with large amounts of vitamin A or iron, I strongly disagree with the researchers’ conclusions based on the way the study was conducted.
Editor’s note: Charles Poliquin is recognized as one of the world’s most suc-cessful strength coaches, having coached Olympic med-alists in 12 different sports, including the U.S. women’s track-and-field team for the 2000 Olympics. He’s spent years researching European journals (he’s fluent in English, French and German) and speaking with other coaches and scientists in his quest to optimize training methods. For more on his books, seminars and methods, visit www.CharlesPoliquin.com. IM