Few food crops are as important to the world as rice. Rice is the major food source for nearly half of the world's population and is especially crucial in Asia, which accounts for about 90% of all rice consumption. But rice is notable in other ways. Because rice is often grown under flooded conditions, it tends to be more prone to contamination than other cereal crops.


The rice plant is adept at pulling heavy metals like mercury, cadmium, and arsenic out of soil and water and concentrating them. As a result, rice can have 10–20 times the arsenic levels of other cereal grains. Even tiny levels of arsenic can affect the immune system and cause problems like heart disease, cancer, and more. Arsenic naturally exists in soil and water, but in levels low enough to avoid health issues. This changes when soil is flooded (often the case when growing rice), as arsenic is unlocked from soil. Much more toxic inorganic arsenic, often found in pesticides, can linger in soil for some time and may be churned up by flooding.


Rice's arsenic issues are not new. British newspapers reported that one third of baby rice for sale in British supermarkets contained unsafe levels of arsenic back in 2008. The US Consumer Products Safety Commission flagged high levels of inorganic arsenic in rice and rice products in 2012. In 2016, the US Food and Drug Administration (FDA) proposed a limit of 100 parts per billion (ppb) of inorganic arsenic in infant rice cereal, matching the level proposed by the European Commission. The FDA calculated that infants reared on rice cereal were consuming three times the level of arsenic (relative to body weight) as adults.


New medical research conducted by the University of Illinois at Chicago and published in the journal Epidemiology shines more light on rice's arsenic problem. Researchers looked at the link between a gluten-free diet and toxic metals in blood and urine. They found that for the 73 participants eating a gluten-free diet, arsenic levels in urine were almost double those of participants on non-gluten-free diets. Mercury levels in blood were 70% higher. Researchers surmise that the arsenic was coming from rice and rice-based ingredients used in place of wheat.


Marketers of rice products have been shy about addressing rice's arsenic contamination issues, but this may be changing. Mighty Rice is a relatively new brand of rice hitting the US market that is imported from the island of Mauritius. The remote island enjoys unusual growing conditions in that rice is grown in non-flooded, rain-fed fields with a minimum of pesticides. This yields rice that is claimed to be "arsenic-free" since arsenic levels have been found to be below the limits of detection (generally around 1–2ppb).


Traditional "clean label" production methods like organic cultivation do not seem to impact arsenic levels. There is generally little difference in arsenic levels between rice grown conventionally, and rice grown organically. Ironically, brown rice (often perceived as healthier) generally contains more arsenic than white rice since arsenic tends to congregate in the husk and bran of rice – parts that are polished off when making white rice. One fix that does reduce arsenic levels is soaking rice overnight before cooking it. This can lower arsenic levels by as much as 80%.


Just as soy had lost some luster as it has evolved into a marker for genetic modification, rice may experience a similar fate if consumers link it with arsenic. Time will tell if "arsenic-free" catches on as a new type of clean label product claim for rice. Even if it does not, it seems clear that food makers will be pressed to be more transparent about rice and arsenic contamination in the future.


By Tom Vierhile