Individuals who consume a gluten-free diet could be at risk for higher exposure to the toxic metals arsenic and mercury, which can lead to cardiovascular disease, cancer and neurological effects, according to a report from University of Illinois at Chicago scientists.

Gluten-free diets are growing in popularity in the U.S., even though less than 1 percent of Americans have been diagnosed with celiac disease, an out-of-control immune response to gluten, a protein found in wheat, rye and barley.

A gluten-free diet is recommended for people with celiac disease, but others often say they prefer eating gluten-free because it reduces inflammation - a claim that has not been scientifically proven. In 2015, one-quarter of Americans reported eating gluten-free, a 67 percent increase from 2013.

Rice Flour

Gluten-free products typically contain rice flour as a substitute for wheat. Rice is known to bio-accumulate certain toxic metals, including arsenic and mercury from fertilizers, soil, or water, but little is known about the health effects of diets high in rice content.

Maria Argos, assistant professor of epidemiology in the UIC School of Public Health, and her colleagues looked at data from the National Health and Nutrition Examination Survey searching for a link between gluten-free diet and biomarkers of toxic metals in blood and urine.

They found 73 participants who reported eating a gluten-free diet among the 7,471 who completed the survey, between 2009 and 2014. Participants ranged in age from 6 to 80 years old.

Rice grown in the U.S. has an average 260 ppb of arsenic, according to one study; but U.S. arsenic intake remains far below World Health Organization - recommended limits. China has set a standard for arsenic limits in food (150 ppb), as levels in rice exceed those in water.

Arsenic Levels

People who reported eating gluten-free had higher concentrations of arsenic in their urine, and mercury in their blood, than those who did not. The arsenic levels were almost twice as high for people eating a gluten-free diet, and mercury levels were 70 percent higher.

“These results indicate that there could be unintended consequences of eating a gluten-free diet,” Argos said. “But until we perform the studies to determine if there are corresponding health consequences that could be related to higher levels of exposure to arsenic and mercury by eating gluten-free, more research is needed before we can determine whether this diet poses a significant health risk.”

In Europe, there are regulations for food-based arsenic exposure, and perhaps that is something we here in the United States need to consider. 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."

Arsenic poisoning is a medical condition that occurs due to elevated levels of arsenic in the body. If exposure occurs over a brief period of time symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.

The study was supported by the National Institutes of Health.

Catherine M. Bulka, Matthew A. Davis, Margaret R. Karagas, Habibul Ahsan, Maria Argos The Unintended Consequences of a Gluten-Free Diet Epidemiology, 2017; 1 DOI: 10.1097/EDE.0000000000000640

Image: Mark Drouin/Flickr

For future updates, subscribe via Newsletter here or Twitter