This 6-month clinical trial tests whether high-selenium lentils, as a whole food solution, can improve the health of arsenic-exposed Bangladeshi villagers. The study entails 400 participants in two treatment groups. All participating households have tubewell water containing ≥100 μg L−1, but over 50% are > 250 μg L−1. In this double-blind study, one group is daily consuming high-selenium lentils from the Canadian prairies, the other, low-selenium lentils grown in another ecozone. At the onset, mid-term, and end of the trial, samples (blood, urine, stool, hair) are collected, and health examinations include testing lung inflammation, body weight and blood pressure. The major outcome will be arsenic excretion in urine and feces, and arsenic deposition in hair. Secondary outcomes also include antioxidant status, and blood lipid profile.