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Although less than 1 percent of Americans have celiac disease, gluten-free diets remain all the rage in the United States. Yet, a new study suggests a potentially harmful ingredients may be hiding in this trendy type of food.

Researchers at the University of Illinois at Chicago report that rice flour, which is used as a substitute for wheat, tends to accumulate toxic metals that can increase the risk of cancer, heart disease and neurological illness. The arsenic and mercury get into the rice via fertilizers, soil and water, and other studies have previously linked the toxic metals to rice.

Though preliminary, the latest findings suggest the possible risks of the diet, if adopted voluntarily, may outweigh its much-touted yet clinically unproven benefits, which include bloating and weight gain.

For the study, authors surveyed about 7,480 people about their diet habits, and found that among the 73 people who reported eating gluten free, levels of arsenic in their urine and mercury in their blood were more concentrated than that of the other survey respondents. In fact, compared with the gluten eaters, arsenic levels were nearly twice as high and mercury levels were 70 percent higher in the gluten-free participants.

Seeing as about one-quarter of Americans reported eating gluten free in 2015 — a 67 percent increase from 2013, according to UIC — it’s safe to say you likely know someone who’s consuming said toxic metals.

“In Europe, there are regulations for food-based arsenic exposure, and perhaps that is something we here in the United States need to consider,” study author Maria Argos, assistant professor of epidemiology in the UIC School of Public Health, said in a news release. “We regulate levels of arsenic in water, but if rice flour consumption increases the risk for exposure to arsenic, it would make sense to regulate the metal in foods as well.”

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Although consuming those metals is linked with poor health outcomes, Argos noted that more study needs to be done before drawing conclusions about whether going gluten-free itself poses a serious health danger.

However, “These results indicate that there could be unintended consequences of eating a gluten-free diet,” Argos said in the release.

Other experts have noted that gluten-free diets, which are necessary for people with celiac, as gluten can be deadly, also may lead to greater consumption of sugar, fat and calories, which manufacturers add to help make up for lost taste.