Factors Associated with Dietary Supplement Use among Healthy Adults of Five Ethnicities: The Multiethnic Cohort Study

The Multiethnic Cohort Study Janet A. Foote ) 1 Suzanne P. Murphy 1 Lynne R. Wilkens 1 Jean H. Hankin 1 Brian E. Henderson 0 Laurence N. Kolonel 1 0 Keck School of Medicine, University of Southern California , Los Angeles, CA 1 Cancer Research Center of Hawaii, University of Hawaii , Honolulu, HI Participants of the Multiethnic Cohort Study in Hawaii and Los Angeles, California, a representative sample of African-American, Native Hawaiian, Latino, Japanese-American, and White adults, completed a baseline questionnaire in 1993-1996 assessing dietary supplement use during the past year as well as demographic, dietary, and other lifestyle factors. Factors associated with supplement use were examined among those who reported an absence of chronic disease (n = 100,196). Use of any of eight supplements at least once per week during the past year ranged from 44% among Hawaiian men to 75% among Japanese-American and White women. Multivitamins were the most frequently reported supplement; 48% of the men and 56% of the women reported regular use. Dietary supplement use was high across all ethnic groups, although levels and length of regular use varied. In all gender-specific ethnic groups, supplement use tended to increase with age, education, physical activity, fruit intake, and dietary fiber intake and to decrease with obesity, smoking, and dietary fat intake. Participants whose lifestyles were healthier were more likely to use dietary supplements. Therefore, it may be difficult to separate the effects of supplement use from other lifestyle factors when studying disease etiology. adult; aged; cohort studies; dietary supplements; ethnic groups; health; minerals; vitamins Abbreviation: NHANES III, Third National Health and Nutrition Examination Survey. - The dietary supplement market is reported to be one of the worlds fastest growing industries (1). The Third National Health and Nutrition Examination Survey (NHANES III) found that 3555 percent of US men and women aged 30 years or older reported use of dietary supplements within the past month (2). The authors suggested that awareness of studies that link specific dietary nutrients with lower disease risk may affect the publics attitudes toward and the use of dietary supplements. Furthermore, the Dietary Reference Intakes recommend that intake of vitamin B12 by older adults who may be at risk of poor absorption and of folate for women capable of becoming pregnant should be from supplemental or fortified sources (3). A modified food guide pyramid for persons older than 70 years of age recommends supplemental intake of both vitamin B12 and calcium (4). These recommendations underscore the necessity of including supplemental sources of intake in any investigation of nutrient and disease associations. The numerous formulations of dietary supplements available present assessment and analytic challenges (57). Despite variations in the composition of supplemental products, reported characteristics of supplement users have been fairly consistent. Several studies have examined lifestyle and demographic associations with dietary supplement use, finding greater use among women, older adults, and those whose levels of education or socioeconomic status are higher (8, 9). NHANES III and previous US national surveys reported higher levels of supplement use among Whites compared with non-Hispanic Blacks and Hispanic adults (2, 7). Dietary differences including lower fat consumption and higher fiber intake have been found among dietary supplement users compared with nonusers (10, 11). Thus, supplement use is associated with a variety of demographic and lifestyle factors. However, most previous studies asked about current use only and were not aimed at minimizing the influence that preexisting chronic disease may have on supplement use. Because supplement use may be different among those with chronic diseases (10, 11), it is more informative to examine use by healthy adults separately. It is also unclear whether the extent of dietary supplement use differs among ethnic groups, especially those who have not been well represented in national surveys. To address these issues, we analyzed information on dietary supplement use among healthy adult participants in the HawaiiLos Angeles Multiethnic Cohort, a large study of five ethnic groups (12). We also examined the influence of demographic, lifestyle, and dietary factors on supplement use. MATERIALS AND METHODS Multiethnic cohort The HawaiiLos Angeles Multiethnic Cohort is a prospective cohort study designed to examine the relation of diet and other risk factors with cancer among representative population groups of five ethnicities: Japanese American, Native Hawaiian, and non-Hispanic White (recruited primarily in Hawaii); and African American and Latino (recruited primarily from the greater Los Angeles, California, area) (12). To achieve as representative a sample of these ethnic groups as possible, drivers license files were used as a primary sampling source since most adults in these areas have drivers licenses. To augment this source, the voter registration file was used in Hawaii, and the Health Care Financing Administration (now known as Centers for Medicare and Medicaid Services) files and census tract information of Los Angeles County were used in the Los Angeles area. On the basis of a comparison of Multiethnic Cohort participants with the 1990 US Census regarding selected variables, the Multiethnic Cohort sample appeared to be well representative of the five ethnic populations in the study areas (12). Quantified 3-day measured food records were used to develop a single, self-administered questionnaire appropriate for all ethnic groups (12, 13). The mailed questionnaire was developed in English and was translated (including back-translation) into Spanish for potential Latino participants, who were offered both the English and Spanish versions from which to choose. Approximately 39 percent of the Latinos completed the Spanish version of the questionnaire (9 percent of the overall cohort). Baseline information was collected during 19931996 for approximately 215,000 adults aged 4575 years. The design and characteristics of the Multiethnic Cohort population have been described previously (12, 13). Baseline questionnaire The baseline questionnaire included various demographic, lifestyle, and medical history items, including migrant status, gender, height, weight, date of birth, education, smoking, sun exposure, physical activity, prior illness, and use of medications. Age group designation was based on the age of the participant at completion of the baseline questionnaire (questionnaire date minus date of birth). Height and weight information was used to determine body mass index (weight in kilograms/height in meters squared), which was categorized as normal (less than 25), overweight (25<30), or obese (30 or more) (14). Regular smokers were defined as subjects reporting lifetime use of (...truncated)