Biomonitoring of nutritional and toxic elements in raw and cooked rice in the Health Effects of Arsenic Longitudinal Study, Bangladesh.

Rice is a staple food and a major dietary exposure source of both nutrient and toxic elements. Rice studies typically focus on individual trace elements rather than cohesively assess multiple elements and typically measure trace elements in raw grain, disregarding cooking effects. Further, almost no studies link cooked rice profiles to biomarkers of internal exposure. Here, we used 106 matched triplets of raw rice, cooked rice, and urine samples from the Health Effects of Arsenic Longitudinal Study in Araihazar, Bangladesh to 1) demonstrate the effect of cooking on 13 essential and toxic elements in rice, 2) characterize elemental profiles of raw rice, cooked rice, and urine, and 3) identify elements in cooked rice that could influence human elemental exposure. Barium and strontium significantly increased after cooking (mean differences of 241 ng/g and 679 ng/g, respectively), while cesium, selenium, molybdenum, and nickel significantly decreased (mean differences of -12 ng/g, -19 ng/g, -202 ng/g, and -125 ng/g, respectively). Iron, cobalt, molybdenum, and vanadium levels in cooked rice significantly correlated with urinary levels (Spearman's ρ = 0.28, 0.29, 0.28, and 0.36, respectively). This suggests that rice may be a previously unidentified exposure source for cobalt, vanadium, and molybdenum - three understudied but potentially toxic elements. Overall, we find that elemental concentrations in raw rice may not reliably reflect dietary exposure, as cooking can introduce external inputs and remove endogenous elements. Integrating biomonitoring data, such as urine measurements, is therefore essential for understanding the contribution of rice to total elemental exposure.