Trends in dietary supplement use in a cohort of postmenopausal women from Iowa.

Although it is widely known that use of dietary supplements is common in the United States, little is known about use patterns among older Americans. The authors examined trends in dietary supplement use and its contribution to total nutrient intake in the Iowa Women's Health Study cohort in 1986 (baseline) and 2004 (follow-up). The proportion of women who reported using dietary supplements increased substantially between baseline (66%) and follow-up (85%). Moreover, a substantial proportion of women reported using multiple dietary supplements, with 27% using 4 or more products in 2004. Dietary supplements contributed substantially to total intake of many nutrients at baseline, and their contribution became relatively greater at follow-up for most nutrients examined. For most nutrients, no decline in intake was observed, as might have been expected in an aging cohort. Rather, intake of many nutrients increased, primarily because of the rising use of dietary supplements. Use of dietary supplements by older individuals is of particular importance because of the potential benefits of maintaining nutrient intake levels despite potentially declining food intake. However, possible risks from obtaining a large proportion of purified nutrients from dietary supplements rather than deriving them from foods should be studied.