In a recent US study, researchers investigated how arsenic exposure from rice may put certain individuals at risk of nonalcoholic fatty liver disease.
Nonalcoholic fatty liver disease (NAFLD) is the most common fatty liver disorder in developed countries. In the US, approximately 30% of adults suffer from NAFLD, which can progress to liver inflammation, fibrosis, and liver cancer later in life. While NAFLD occurs primarily in those who are obese, it is also thought to be influenced by genetics and exposure to environmental pollutants.
Recent evidence has suggested that arsenic may be to blame. Despite government regulations to control arsenic levels in public drinking water, the heavy metal can accumulate in the soil, where its then absorbed by certain plants. Rice, specifically, has been known to store excess arsenic in the grain, which is then transferred to humans when consumed. In the U.S., every quarter cup per day increase in rice consumption raises arsenic levels in the blood by 14%.
Arsenic Leads to Fatty Liver Disease in Mice
To investigate a potential link between arsenic exposure and increased risk of NAFLD, scientists first looked to mouse models. Researchers found that mice exposed to arsenic experienced the highest degree of liver damage and inflammation, even more so than those fed a high-fat diet.
To determine whether the same link could be observed in humans, scientists surveyed 8,516 Americans of varying age, weight, sex, and ethnicity between 2005 and 2014. To avoid performing liver biopsies on every participant, NAFLD was assessed instead using blood alanine aminotransferase (ALT) levels, a liver enzyme often elevated in patients with fatty liver diseases. Arsenic exposure was assessed using urine samples, which reflects the patient’s average arsenic uptake in the last three days. The results were recently published in Environmental Health.
Certain Ethnic Groups More at Risk
The researchers found that higher arsenic levels in the urine did reflect an increased likelihood of NAFLD. This was true regardless of the individual’s weight, meaning obesity didn’t seem to play as large a role as previously thought. However, the researchers did find that being obese made things worse, with obese patients exposed to arsenic having even higher ALT levels.
The scientists also found that certain ethnic groups were more likely to be exposed to arsenic than others. The most significant association was found amongst Mexican Americans, with other Hispanics, African-Americans, and Asian-Americans also at higher risk. The researchers believe that this may be associated with variations in cultural diets. Those where rice was a staple food were more likely to be exposed to higher levels of arsenic, however, the scientists would have to determine each participant’s diet to be sure.
The research team is now looking to confirm this hypothesis by surveying patients diagnosed with NAFLD. By understanding who might be at risk of the disease, the team hopes to develop community programs to help those affected early on, before severe liver damage and cancer can develop. This is the first study to evaluate this association in humans and the researchers hope that this study, along with future research, can help to identify the biological mechanisms involved. They also hope this study will lead to more strategies to prevent or reduce the effects of arsenic exposure.
Written by Calvin J. Chan, B.Sc.
Reference: Frediani, J.K., Naioti, E.A., Vos, M.B., Figueroa, J., Marsit, C.J. and Welsh, J.A. (2018). Arsenic exposure and risk of nonalcoholic fatty liver disease (NAFLD) among U.S. adolescents and adults: an association modified by race/ethnicity, NHANES 2005-2014. Environmental Health. 17:6.