While often praised for its nutritional benefits, brown rice may pose hidden risks for children under five, with some exceeding international safety thresholds for arsenic exposure.
Study: Arsenic content and exposure in brown rice compared to white rice in the United States. Image Credit: Bowonpat Sakaew / Shutterstock
In a recent study published in the journal Risk Analysis, researchers compared arsenic exposure and related risks between white and brown rice consumers in the United States (US).
Rice consumption in the US has increased in the past five decades. It has been assumed that brown rice is healthier than white rice due to its higher fiber and micronutrient content. Although white rice and brown rice come from the same species, brown rice is less processed and has some germ and bran content, whereas white rice is refined to strip the germ and the bran.
Rice milling and processing can lead to visually contrasting grain and differences in nutritional content, price, public perception, appearance, cooking methods, toxic element levels, and taste. Brown rice is more desirable for some due to its nutritional benefits and less desirable for others due to cultural preferences, price, taste, and limited storage life.
While the germ and bran of brown rice retain much of the grain’s nutrients, they also contain higher levels of toxic elements, including arsenic. As such, brown rice has higher arsenic than white rice. However, the amount of arsenic in rice can vary widely due to factors such as rice variety, where it is grown, and agricultural or processing practices. This is particularly concerning because even low-level arsenic exposure has been linked to health risks, such as cardiovascular disease and cancer.
The study and findings
In the present study, researchers compared arsenic exposure from white rice and brown rice consumption in US consumers. First, they performed a literature review regarding the nutritional aspects of both types of rice. Next, they used the “What We Eat in America” database to ascertain the average American's rice consumption.
The database was drawn from the dietary intake component of the National Health and Nutrition Examination Survey, which uses 24-hour dietary recall data to examine the diet. Using the average rice intake values, the team computed the average daily dose of arsenic. Rice bran has a substantially higher concentration of inorganic arsenic than rice endosperm, which increases arsenic levels in brown rice compared to white rice.
Moreover, the proportion of arsenic that is inorganic was lower in US rice (48% for brown rice and 33% for white rice) than in non-US sources (65% for brown rice and 53% for white rice). Absolute concentrations of total and inorganic arsenic in US rice were similar to global averages. Here, the use of the word “concentrations” refers to the proportion, not the absolute amount, of inorganic arsenic. Percentages varied highly from 10%–90%, with 54% commonly referenced, in contrast to US rice having lower percentages (10% to 69%), with 40% widely referenced. The reasons for this variation are not fully understood and may involve differences in soil, water, and rice genotype. This suggested a higher risk of non-domestic rice for Americans.
The overall difference in arsenic levels was minimal between US rice (0.278 μg/kg in brown rice and 0.224 μg/kg in white rice) and the global mean (0.277 μg/kg in brown rice and 0.231 μg/kg in white rice). Further, children under five years were the heaviest rice consumers per unit bodyweight (bw). In the total US population, the mean rice intake was 0.52, 0.81, and 0.55 g/kg bw/day for those aged 0–6, 6–24, and 24–60 months, respectively.
In contrast, the corresponding mean intake of the subgroup specifically eating rice regularly (eaters-only subpopulation) was 1.6, 1.09, and 0.77 g/kg bw/day, respectively. The mean rice intake for all age groups was 0.27 g/kg bw/day for the total US population and 0.37 g/kg bw/day for the eaters-only subgroup.
Further, the team observed a higher daily intake of brown rice in children aged 6–24 months (2.14 g/kg bw/day) and white rice in those aged 6–24 months (1.51 g/kg bw/day) and 24–60 months (1.55 g/kg bw/day) in the eaters-only subgroup than in the total population. The daily intake of arsenic was 0.295 μg/kg bw/day for the brown rice eaters-only subpopulation aged 6–24 months, exceeding the safe levels (0.21 μg/kg bw/day). Importantly, the daily intake of inorganic arsenic for the brown rice eaters-only subpopulation aged 0–6 months was also elevated (0.221 μg/kg bw/day), exceeding the safety threshold.
Moreover, elevated arsenic intake was observed in the eaters-only subpopulation for white and brown rice in children under 18 years. Children aged 6 months or below had lower arsenic exposure and intake rates in the general population, although specific subgroups of infants had intakes that exceeded recommended thresholds. Exposure to inorganic arsenic from specific white or brown rice products was relatively low for adult subpopulations.
The study also notes that certain nutrients present in brown rice, such as some micronutrients, might help the body process and excrete arsenic more efficiently, although more research is needed to understand if these potential benefits offset the increased arsenic exposure. Additionally, the authors acknowledge limitations in the available data, including variations in arsenic measurement methods and the need for more direct comparisons across rice types and origins. The findings about variability in arsenic content are based on currently available studies, and more research is needed to clarify these patterns.
Conclusions
In sum, the findings indicate a potential risk of harmful exposure to arsenic from brown rice in children under five years. Nevertheless, most Americans' daily exposure to inorganic arsenic was not high enough to pose a higher risk of adverse health outcomes. The overall risk to adult consumers in the US appears limited based on current average exposures.
Further research is needed to examine whether the potential risk of higher arsenic in brown rice could be mitigated by the bran's nutritional benefits. The authors recommend that future studies consider the variability in rice sources and processing and the possible benefits of nutrients that may help reduce arsenic toxicity.
The balance between the health benefits of whole grains and the food safety risks from arsenic exposure remains an important consideration for dietary recommendations, especially for young children and other vulnerable groups.