Dietary Supplement Use Underreported in the Office

Abstract & Commentary

Synopsis: In this study, half the patients who took dietary supplements and almost half who took nonprescription medications did not report them to their health-care provider on the written questionnaire, even though this information was requested.

Source: Hensrud DD, et al. Mayo Clin Proc 1999;74:443-447.

To compare the use of dietary supplements and nonprescription medications, the researchers conducted a prospective study of 200 subjects randomly selected from patients undergoing a periodic health examination. Written information on self-reported use of supplements and nonprescription medication was obtained as part of a comprehensive medical questionnaire. Subjects were then interviewed and asked about usage and reasons for usage.

The prevalence of the use of dietary supplements was 30.5% by written self-report in comparison with 61% reported during the structured interview. Use of nonprescription medication on the questionnaire was 24.5%; reported use when interviewed was 42.5%. Multivitamins (41.5%), vitamin E (24%), and vitamin C (23%) were the most common dietary supplements taken; aspirin (16.5%) and ibuprofen (13%) were the most common nonprescription medications taken. Most frequently, patients indicated that they were using supplements to promote health.

Half the patients who took dietary supplements and almost half who took nonprescription medications did not report them to their health care provider on the written questionnaire, even though this information was requested. Patients should be specifically and orally asked about usage.

Comment by John RLa Puma, MD, FACP

These Rochester, Minnesota, investigators achieved an 83% response rate from both community residents and from executive patients. Ninety-nine percent of their community patients were white; 84% of the executives were male; overall, 62% were male. Community patients appeared to use nonprescription medications but not dietary supplements less often than did executives. These data were not analyzed for statistical significance, and educational and socioeconomic data about each group were not reported. Most patients took supplements to "promote health," and many took them to "prevent disease"—only two of 122 respondents took them to treat disease.

Why isn’t a questionnaire enough to get accurate information? Patients may forget they are taking supplements, forget to record supplement names on a lengthy questionnaire, be unsure about how or whether to tell, consider them unimportant to their visit, or fear ridicule or embarrassment. In this study, a nonphysician asked about supplements, person to person—all it took to double the number of accurate responses.

Data from the 1992 National Health Interview Survey showed that 24% of the U.S. population used vitamin and mineral supplements daily. Similar data gathered since then suggest accelerated use. The boom in supplements started with the 1994 Dietary Supplement Health and Education Act, which essentially deregulated the area.

Ask the patient what he or she is taking, even if your previsit written assessment asks patients directly. Supplements should be considered medication—by patients and providers. (Dr. La Puma is Professor of Nutrition, Kendall College, Director C.H.E.F. Clinic, C.H.E.F. Skills Research, Alexian Brothers Medical Center, Elk Grove Village, Ill.)