The “Typical” Asian Diet Is Anything But: Differences in Dietary Exposure to Metals among Subgroups of U.S. Asians

The U.S. Asian population consists of many culturally and geographically diverse ethnic subgroups. In nationally representative population-based samples, these groups often are lumped together in race categories such as “Asian” or “Other,” which can mask differences in the ways that environmental exposures affect health in subpopulations. In a pair of new studies in EHP, researchers assess diet, dietary intake of metals, and associated biomarker concentrations across three Asian subgroups. A 2014 analysis by the Centers for Disease Control and Prevention (CDC) found that U.S. Asians overall tended to have higher levels of several metals and metalloids in their blood and urine than white, black, or Hispanic populations. These substances have been linked to cancer, heart disease, developmental defects, damage to the nervous system, and kidney failure. However, the 2014 analysis was unable to assess whether exposures varied among Asian subgroups. Such distinctions could have important implications for preventing and treating disease. Asian Americans make up about 6% of the U.S. population. If researchers sampled Asian Americans in proportion to their total population, just 6 out of every 100 research participants would be Asian. That may not be a large enough sample to draw out statistically significant differences among ethnic Asian subgroups. In the 2011–2012 iterat ion of its National Health and Nutrition Examination Survey (NHANES), the CDC oversampled Asians, meaning the surveyors included a greater number of Asians in proportion to their representation in the U.S. population. They also collected demographic information on three Asian subgroups: Chinese and Asian Indian—each accounting for about 20% of the U.S. Asian population—as well as “Other Asian,” a group that census figures indicate is composed mainly of Filipino, Vietnamese, Korean, and Japanese Americans. “It’s a big deal that NHANES did this, because it gives us an unprecedented opportunity to study in depth the national health profile of a particular group of people,” says Moon Chen, an expert in cancer health disparities who works at the University of California, Davis. Chen was not involved with the new research. In one of the two studies, researchers at The University of Texas Health Science Center at Houston (UTHealth) used NHANES data to compare blood and urine levels of lead, mercury, arsenic, and cadmium among the three Asian subgroups. They found that levels of mercury, arsenic, and cadmium were similar among Chinese and Other Asians, but lower among Asian Indians. Asian Indians, however, had slightly higher blood lead levels than the other two groups. The researchers posit that these higher blood lead levels could have been associated with Asian Indians’ common use of certain spices and cosmetics, since elevated levels of lead have been found in the spice turmeric and in eye makeup known as kohl, or surma. U.S.-born Asians generally had lower average levels of all four metals than Asians born outside the United States. Sex, age, education level, smoking status, and fish consumption also predicted biomarker levels of specific metals in some Asian subgroups. Food consumption is known to be a major source of exposure to mercury, arsenic, and cadmium in the general population. Among the Asian populations, fish contributed the most mercury and total arsenic, while rice contributed the most inorganic arsenic, which is the more toxic form of the metalloid. Vegetables, cereal grains, fruits, and dairy products contributed the most cadmium among nonsmokers (tobacco is a major source of this metal). In the second study, the researchers compared the three Asian subgroups with other U.S. racial/ethnic groups in terms of food consumption and associated metal intake levels. They combined data from the NHANES dietary questionnaire, the