Gluten-free diets related to high levels of arsenic, mercury

Individuals who adopt a gluten-free diet are putting themselves at risk for uncommonly high levels of arsenic and mercury, according to the findings of a recent study published in Epidemiology.

“Despite (less than) 1% of Americans having diagnosed celiac disease, an estimated 25%  of American consumers reported consuming gluten-free food in 2015, a 67% increase from 2013,” wrote the authors  of the study, at the University of Illinois at Chicago. “Despite such a dramatic shift in the diet of many Americans, little is known about how gluten-free diets might affect exposure to toxic metals found in certain food,” they noted.

Data collected from the National Health and Nutrition Examination Survey (NHANES) were analyzed, which included self-reported questionnaires in which subjects indicated what type of diet they were on, if any. Data on those who indicated that they followed a gluten-free diet were analyzed to determine if their urinary and blood biomarkers indicated any exposure to toxic metals. A total of 7,471 subjects from the NHANES were included in the analysis.

“We accounted for the complex sampling design of NHANES (by) using Taylor series linearization and sampling weights, per the NHANES analytic guidelines, to ensure unbiased and nationally representative estimates,” the authors explained.

A total of 73 subjects identified themselves as following a gluten-free diet. Within this group, the mean total arsenic level in urine was found to be 12.1 mcg/L, compared to 7.8 mcg/L for the other 7,398 subjects. Levels of dimethylarsinic acid averaged 5.3 mcg/L for those who were gluten free, but only 3.7 for everyone else, while cadmium and lead levels were also slightly higher for gluten-free individuals: 0.18 mcg/L vs. 0.16 mcg/L, and 0.40 mcg/L vs. 0.37 mcg/L, respectively.

Blood analyses showed that total mercury levels were also substantially higher in the gluten-free group, at a mean of 1.3 mcg/L compared to 0.8 mcg/L. While cadmium levels were the same between  the two – both  showed a mean level of 0.29 mcg/L lead measure 1.1 mcg/dL and inorganic mercury measured 0.30 mcg/L, compared to 0.96 mcg/L and 0.28 mcg/L in everyone else, respectively.

Geometric mean ratios showed that total arsenic, total arsenic 1, and total mercury levels had the largest disparity between the two groups.

Total arsenic registered a 1.5 (95% confidence interval, 1.2-2.0), total mercury a 1.7 (95% CI, 1.1-2.4), and total arsenic 1 a 1.9 (95% CI 1.3-2.6), meaning the gluten-free group had nearly double the risk for higher levels than those on other diets.

“These findings may have important health implications since the health effects of low-level arsenic and mercury exposure from food sources are uncertain but may increase the risk for cancer and other chronic disease.  It was concluded that “future studies are needed to more fully examine exposure to toxic metals from consuming gluten-free foods.”