| Dietary Intake and Arsenic Methylation in a U.S. Population Craig Steinmaus,1,2 Kenichi Carrigan,2 Dave Kalman,3 Raja Atallah,3 Yan Yuan,1 and Allan H. Smith1 1Arsenic Health Effects Research Program, School of Public Health, University of California, Berkeley, California, USA; 2Division of Occupational and Environmental Medicine, University of California, San Francisco, California, USA; 3School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA Abstract
Millions of people worldwide are exposed to arsenic-contaminated drinking water, and ingestion of inorganic arsenic (InAs) has been associated with increased risks of cancer. The primary metabolic pathway of ingested InAs is methylation to monomethyl arsenic (MMA) and dimethyl arsenic (DMA) . However, people vary greatly in the degree to which they methylate InAs, and recent evidence suggests that those who excrete high proportions of ingested arsenic as MMA are more susceptible than others to arsenic-caused cancer. To date, little is known about the factors that determine interindividual differences in arsenic methylation. In this study, we assessed the effect of diet on arsenic metabolism by measuring dietary intakes and urinary arsenic methylation patterns in 87 subjects from two arsenic-exposed regions in the western United States. Subjects in the lower quartile of protein intake excreted a higher proportion of ingested InAs as MMA (14.6 vs. 11.6% ; p = 0.01) and a lower proportion as DMA (72.3 vs. 77.0% ; p = 0.01) than did subjects in the upper quartile of protein intake. Subjects in the lower quartile of iron, zinc, and niacin intake also had higher urinary percent MMA and lower percent DMA levels than did subjects with higher intakes of these nutrients. These associations were also seen in multivariate regression analyses adjusted for age, sex, smoking, and total urinary arsenic. Given the previously reported links between high percent MMA and increased cancer risks, these findings are consistent with the theory that people with diets deficient in protein and other nutrients are more susceptible than others to arsenic-caused cancer. Key words: arsenic, drinking water, environmental health, metabolism, nutritional susceptibility. Environ Health Perspect 113:1153-1159 (2005) . doi:10.1289/ehp.7907 available via http://dx.doi.org/ [Online 10 May 2005]
Address correspondence to A.H. Smith, Arsenic Health Effects Research Program, School of Public Health, 140 Warren Hall, University of California, Berkeley, CA 94720-7360 USA. Telephone: (510) 843-1736. Fax: (510) 843-5539. E-mail: ahsmith@berkeley.edu Primary funding for this study was provided by the California Cancer Research Program grant 9900563V. Additional support was provided by National Institute of Environmental Health Sciences grants K23 ES11133 and P42 ES04705, and the Center for Occupational and Environmental Health. The authors declare they have no competing financial interests. Received 6 January 2005 ; accepted 10 May 2005.
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