A new report on the safety of supplement use in older women has been released from the Iowa Women’s Health Study (1).
The study tracked women 55 to 69 years old, almost entirely white, for an average of 19 years. After adjusting for age, education, place of residence, diabetes, high blood pressure, body mass index, waist to hip ratio, hormone replacement therapy, physical activity, smoking, energy, alcohol, saturated fatty acids, whole grain products, fruits, and vegetables, they found the following:
– Multivitamins were associated with a 6% increase in mortality (1.06, 1.02-1.10).
– Iron (1.10, 1.03-1.17) and copper (1.45, 1.20-1.75) were associated with an increased risk for mortality.
– Vitamin B6 (1.10, 1.01-1.21), folic acid (1.15, 1.00-1.32), magnesium (1.08 1.01-1.15), and zinc (1.08, 1.01-1.15), were all associated with a borderline statistically significant increased risk of mortality.
– Vitamin A, beta-carotene, vitamin B complex, vitamin C, vitamin D, vitamin E, and selenium supplements were not associated with an increase in mortality.
– Calcium supplements were associated with a decreased risk of mortality (0.91, 0.88-0.94).
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There was not a lot of data on amounts, except for iron and calcium. The groups with an increased risk of mortality from iron were taking fairly hefty amounts of iron, with the biggest risks associated with 50 to > 400 mg/day! That is a lot of iron ‒ the RDA for women 51 to 70 years old is 8 mg.
The levels of calcium associated with the reduced risk of mortality were basically anything less than 1,300 mg per day.
The authors summed up their findings with, “In conclusion, in this large prospective cohort of older women, we found that most dietary supplements were unrelated to total mortality rate. However, several commonly used dietary vitamin and mineral supplements were associated with increased total mortality rate, most strongly supplemental iron; calcium showed some evidence of lower risk.”
This study is just one piece to a very large puzzle, and I would not take it to mean anything conclusive. If you look at the entire body of research, results regarding supplements have been quite mixed and this tends to make me think they do not have a strong effect on mortality one way or the other, although there is still more to be learned.
One thing I would take away from this study is that it is further evidence that people should not take iron supplements, especially more than the RDA, unless under the guidance of a physician.
As for vegans, studying supplements in terms of their ability to decrease or increase mortality in a population that does not have acute deficiencies is not the same as for people whose diets are significantly lower than the DRIs for particular nutrients. This study would not give me any reason to change my recommendations.
1. Mursu J, Robien K, Harnack LJ, Park K, Jacobs DR. Dietary Supplements and Mortality Rate in Older Women: The Iowa Women’s Health Study. Arch Intern Med. 2011;171(18):1625-1633. | Link