All plants take up the nutrients they need from soil. When soil is polluted with toxic elements, such as cadmium, lead, arsenic, and mercury, plants take them up because they mistake them for essential nutrients. Long-term exposure to toxic metals can increase our risk of various diseases. Regulatory agencies have set limits for the presence of most of these elements in food, but despite mounting evidence that rice is a dietary source of arsenic, no regulations on arsenic have been set. Depending on the foods you eat, metal exposure will vary between each individual.
Gluten-free (GF) products depend heavily on rice as a substitute for wheat. While other types of grains are included in the gluten-free diet, rice is by far the most commonly used replacement in dietary staples, such as pasta and baked goods. Unfortunately, the rice farming method of growing rice in flooded soil means rice can contain a higher concentration of arsenic than other cereal crops. The flooding of rice paddies also encourages the uptake of mercury. Despite this, comparisons between the toxic metal content of gluten-free foods and standard food products are scarce.
In a recent study published in the journal, Food Chemistry, Tracy Punshon, PhD, and Brian Jackson analyzed a variety of gluten-free foods and their gluten-containing counterparts to measure these toxic elements and essential nutrients. They tested 19 different rice grains, three rice flours, and 19 non-rice flours (e.g., corn, corn masa, whole wheat, all-purpose wheat, sprouted wheat, spelt, millet, oat, buckwheat, chickpea, coconut, almond, and amaranth), as well as other popular grains (e.g., black chia seed and tricolor quinoa). Of the prepared products tested, most of the gluten-free products listed rice as one of the top three ingredients.
The researchers found that the arsenic concentration in rice and rice-containing products was significantly higher than foods made with other grains, and that brown rice was higher in arsenic because arsenic accumulates in the outer bran layers. An unexpected finding was that rice products also contained significantly more methylmercury and lead than non-rice products. However, the levels of mercury found in rice were one hundred times lower than the levels measured in seafood. Wheat, on the other hand, contained the highest levels of cadmium, but there is currently no perceived risk from cadmium levels in wheat. Rice was lower overall in nutrients, particularly selenium and iron, than wheat or any of the other non-gluten-containing grains. This is particularly important because nutrients have a strong protective effect against toxic metals.
“Based on the products we measured,” Punshon explained, “a rice-based GF diet potentially contains more contaminants than a non-GF diet…People on a GF diet, particularly children, should eat as wide a variety of GF grains as they can, which our study suggests will both decrease contaminant exposure and increase essential nutrient intake.”
If the concentrations of these elements found in the samples are used to estimate dietary arsenic intake overall, the arsenic levels suggest caution for people eating gluten-free, especially because regulations on the level of arsenic in rice have still not been passed into law. This is particularly a concern with overuse of rice as a substitution for wheat. A well-balanced variety of other grains would reduce arsenic exposure and increase nutrient ingestion as well.
Click here to read the full study.
Visit our page on what is safe to eat on the gluten-free diet to learn more about nutritious gluten-free alternatives.