Gluten-free foods are a sneaky source of toxic heavy metals, reveals new research from the University of Illinois at Chicago. Among some 7,500 Americans studied, those who followed a gluten-free diet had twice as much arsenic and 70 percent more mercury in their bloodstream than those who consumed conventional foods. Chronic exposure to these toxins can increase your risk of certain cancers, heart and lung diseases, and neurological problems.
These findings are troubling given that gluten-free foods have skyrocketed in popularity in recent years. An estimated 25 percent of Americans now consume these items at least some of the time. The number of people who eat only gluten-free foods — whether they have celiac disease, a gluten sensitivity, or a misguided notion that ousting gluten will lead to weight loss — tripled between 2009 and 2014.
Despite any real or perceived health benefits, a gluten-free diet introduces arsenic and mercury through heavy consumption of rice, says lead study author Maria Argos. However, unlike many Asian and Central American cultures that eat rice nearly every day, gluten-free folks in the U.S. aren’t necessarily feasting on stir-fry and risotto. In fact, in this study, there was no difference in consumption of straight rice between the gluten-free and conventional-diet groups.
For that reason, Argos believes the bulk of arsenic and mercury exposure comes through rice-based ingredients in processed foods. Gluten-free breads, cereals, crackers, pastas, pizza crusts, and protein bars are often made with rice flour, rice starch, or brown-rice syrup in lieu of gluten-containing wheat, rye, oat, and barley ingredients. Therefore, according to Argos, “people on gluten-free diets may be consuming more rice products than they realize.”
There are two types of arsenic: organic and inorganic. Both can be toxic, and both have been detected in rice. Because of the unique makeup of the rice plant, it sucks up heavy metals from the soil and water more readily than do other crops. These toxins then accumulate in the grain and bran. “There are certain regions of the world where the rock and soil is naturally enriched with organic arsenic and some areas that have elevated arsenic in the water,” Argos says. “Also, in the past, inorganic arsenic was used as a pesticide, and it can persist in the soil and contaminate rice crops.”
Since there has been very little research on the health impacts of arsenic in food, Argos says it’s tough to know what level is safe. But based on studies of arsenic in drinking water, which remains our main exposure, it’s clear that inorganic arsenic is a carcinogen. “It’s associated with lung, bladder, and non-melanoma skin cancers,” Argos says. “Some evidence has also linked it to increased risk of hypertension, heart attacks, strokes, and lung diseases like asthma, bronchitis, and COPD.”
The health effects of organic arsenic are more of a mystery, especially when it comes from rice. “We know that the organic arsenic found in fish is nontoxic, but the form found in rice is different,” Argos says. “We don’t know the health ramifications of that type. We also don’t know how much the beneficial nutrients in rice counterbalance the contaminants you’re ingesting.”
Mercury, on the other hand, which accumulates in fat stores and persists in the body for a long time, is a well-documented health hazard. “Mercury exposure is associated with neurotoxic outcomes and potentially cardiovascular disease,” Argos says.
If you must eat gluten-free, the best way to limit your exposure to these toxic heavy metals is to diversify your menu. “If you eat processed foods or gluten-free substitutes for gluten-containing foods, just be aware of what’s in those specialty products,” Argos says. “Read ingredients lists, and if you’re consistently seeing rice flour, puffed rice, brown rice syrup, and other rice-based ingredients, choose other foods to ensure you’re not relying so heavily on rice.” And remember: Gluten-free whole foods, including fruits, veggies, legumes, and lean meats, are usually a safer, more nutritious bet than processed anything.