A few weeks ago the Archives of Internal Medicine published a study that used data from the Iowa Women’s Health Study to assess supplements and mortality.
Since then, besides reading the actual article, I have read a dozen articles and news pieces reacting to the study’s results. Some of these came out almost as soon as the article came out making sweeping, sensationalist claims. On one end, some say these results are meaningless, while at the other end, people think we should swear off all supplements for good.
So what exactly was the study that has been creating such a stir and what is the takeaway message?
Jaakko Mursu and other researchers at the University of Minnesota analyzed self-reported nutritional and mineral supplement use of 38,772 postmenopausal women (mean age = 61.6 years at baseline in 1986), with the goal of finding out the relationship between supplement use and total mortality.
The use of 15 supplements – multivitamins, vitamins A, beta-carotene, B6, folic acid, B complex, C, D, and E, iron, calcium, copper, magnesium, selenium, and zinc – were examined in 1986, 1997 and 2004.
Researchers used the Harvard Service Food Frequency questionnaire at baseline and in 2004. The foods on the questionnaire were a compilation of the most commonly eaten foods in 1985.
Murso et al did look at some confounding factors, and also found that in 1986 and similarly in 2004, supplement users had fewer incidences of diabetes, lower blood pressure, were less likely to smoke, had a lower BMI and waist to hip ratio, were less likely to live on a farm, were more educated, were more physically active, were more likely to use hormone replacement therapy, consumed fewer calories and fat and more protein, carbs, polyunsaturated fat, alcohol, whole grains, fruits, and vegetables than did nonusers. In other words, they seemed healthier over all.
Supplement use throughout the years increased dramatically. In 1986, 62.7% of women took at least 1 supplement, 75.1% in 1997, and 85.1% in 2004. I am sure the number is significantly higher now.
Results showed that use of multivitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper were correlated with an increased risk of mortality (2.4% increased rate of death). The association with iron was the greatest, and there was a dose-response relationship was found. For vitamins A, C, D, and E, and selenium and zinc, there was no dose-response relationship, and for vitamins A and D there was no relationship at all. As well, there was an inverse relationship with calcium, with a significantly lower risk of mortality (3.8%), which is especially noteworthy because some prior studies had shown the opposite results.
Iron is serious because it “was consistent across shorter intervals, strengthened with multiple use reports and with increasing age at reported use.” Other papers also said why the iron finding was an important one, such as it is easy to get too much of since foods like cereal are often fortified with it, and there is an often undiagnosed genetic disorder, hemochromatosis, for which too much iron can cause diabetes, liver disease, heart failure and impotence. This disorder affects one in every 200-300 people.
The authors postulate that iron might be implicated because it “catalyze[s] reactions that produce oxidants and thus promote oxidative stress. However, we cannot rule out the possibility that the increase in total mortality rate was caused by illnesses for which use of iron supplements is indicated,” such as anemia, which could be a result of long-term illness, major injury, and/or surgical procedures (among other things).
All vitamins and minerals in excess, though, cause various problems, and different articles explain those further and in-depth.
The researchers did not look at cause of death, so this study does not show any causal relationship between supplements and death, and it would be premature to stop taking supplements. However, supplements are just that: They are meant to supplement a diet that is hopefully well-balanced and micronutrient-rich. We don’t even know the nutritional status of the group studied. Supplements should not be used instead of whole foods, and they shouldn’t be used for preventative measures, but only when nutrition gaps are present. This is a note of caution, however, and even more so now with the recent research on vitamin E and prostate cancer.
randi morse, randi.morse@gmail.com, newton, ma
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