Introduction: Arsenic is ubiquitous in the environment as an element of the earth’s crust. Human exposure predominantly occurs through ingestion of contaminated drinking water and arsenic-rich foods such as seafood and rice. Chronic exposure to inorganic arsenic has been associated with certain cancers, and more recently with cardiovascular disease and diabetes that are common among the obese. However, little is known about the specific relationship between inorganic arsenic exposure and obesity.
Hypothesis: We assessed the hypothesis that inorganic arsenic exposure was correlated with obesity in the general population of the United States.
Methods: We analyzed a representative sample of 4,105 adults from the U.S. population using data from the 2007-2010 National Health and Nutrition Examination Survey (NHANES). Arsenobetaine and arsenocholine concentrations, which are forms of organic arsenic, were subtracted from total urinary arsenic concentrations to estimate the amount of inorganic arsenic in urine as a biomarker of exposure. These values were standardized by urinary creatinine to control for hydration status. Obesity was assessed using measured body mass index (BMI) in kg/m2 and waist circumference in cm. Crude and adjusted survey-weighted linear regression models were performed.
Results: Creatinine-adjusted urinary inorganic arsenic concentrations were inversely associated with log-transformed BMI (p for trend = 0.0003) and log-transformed waist circumference (p for trend = 0.0001). The highest quintile of inorganic arsenic concentration (>10.4 to 483.3 μg/L) was associated with a 5% (95% CI: 3 to 8%) lower BMI and a 4% (95% CI: 2 to 6%) smaller waist circumference compared to the lowest quintile (0 to 2.3 μg/L). Adjustments for age, gender, race, thyroid problems, diabetes, smoking status, seafood consumption, rice consumption, red blood cell folate, serum folate, socioeconomic status, and survey cycle did not appreciably alter these results. There was no evidence of effect modification between urinary inorganic arsenic concentrations and covariates on obesity.
Conclusions: While inorganic arsenic exposure has generally been positively associated with obesity-related diseases, we observed a negative association between urinary inorganic arsenic concentrations and obesity in this representative cross-sectional analysis. It is unclear if this is a true association in which inorganic arsenic exposure is protective against obesity, or if this finding reflects differential arsenic absorption, metabolism, or storage by adiposity level.