A gluten-free diet may be linked to higher levels of mercury and arsenic, according to study

Roughly 25% of Americans consume gluten-free foods because they have celiac disease, because their guts are sensitive to gluten or because they feel healthier ditching gluten products. But there might be some unintended consequences of a diet that avoids gluten. 

A new study from the journal Epidemiology found that following a gluten-free diet that relies on rice-based products could put a person at greater risk for having higher levels of arsenic and mercury in their system.  

The study: Researchers analyzed data from a national health study (the National Health and Nutrition Examination Survey), examining the behavior of 7,471 participants, 73% of whom self-reported being on a gluten-free diet. Researchers then examined blood and urine samples to identify levels of mercury and arsenic exposure. 

The results: Researchers found that participants who followed gluten-free diets had higher levels of arsenic and blood mercury. It was estimated that people who ate gluten-free had almost double the concentration of arsenic in their urine compared to people who consumed gluten normally.

Rice may be the culprit

Researchers speculated that increased exposure to arsenic and mercury could be attributed to rice, which is often substituted as the primary grain for people who follow gluten-free diets. Many commercial gluten-free products use rice flour or rice milk.

It's well-known among scientists that rice is a source of arsenic. According to the Food and Drug Administration, rice absorbs more arsenic from soil than other crops. Arsenic occurs in the Earth's crust and seeps into soil naturally, LiveScience reported, and it's also present in many pesticides. The Environmental Protection Agency estimates that arsenic can stay in soil for up to 45 years.

"To our knowledge, this is the first analysis to suggest that Americans on gluten-free diets may be exposed to higher levels of arsenic and mercury," researchers wrote. 

While everyone has some arsenic and mercury in their body, it's unclear whether the long-term effects of a gluten-free diet will be as harmful as the long-term effects of consuming water containing arsenic. Exposing yourself to arsenic in drinking water over a long period can result in skin disorders, diabetes, high blood pressure or cancer, according to the Centers for Disease Control and Prevention. 

The amount of arsenic and mercury in the gluten-free study participants was nowhere near toxic, but researchers noted more research is needed to suss out what the long-term health effects might be. 

If you don't have celiac disease and instead eat gluten-free for health reasons, experts point out that ditching gluten could mean you miss out on important nutrients, too. Gluten-containing breads and cereals are a major source of B vitamins in American diets, the Harvard Health blog reported, pointing out that gluten-free breads and cereals are typically not fortified with vitamins.