Higher concentrations of carbon dioxide are associated with reductions in protein and multiple key nutrients in rice, according to a new field study by an international team that included scientists from the University of Washington School of Public Health.

The study, published in Science Advances, shows for the first time that rice grown at concentrations of atmospheric CO2 expected by the end of this century has lower levels of four key B vitamins. The findings also support research from other field studies showing rice grown under higher CO2 concentrations has less protein, iron and zinc.

“Rice has been a dietary staple for thousands of years for many populations in Asia and is the fastest growing food staple in Africa,” said co-author Kristie Ebi, director of the UW Center for Health and the Global Environment and professor of global health and environmental and occupational health sciences. “Reductions in the nutritional quality of rice could affect maternal and child health for millions of people.”

Field studies showed that average Vitamin B1 (thiamine) levels decreased by 17.1 percent; average Vitamin B2 (riboflavin) by 16.6 percent; average Vitamin B5 (pantothenic acid) by 12.7 percent; and average Vitamin B9 (folate) by 30.3 percent. The researchers reported no change in levels of Vitamin B6 or calcium, while Vitamin E levels increased for most strains. They also found an average 10.3 percent reduction in protein, 8 percent reduction in iron and 5.1 percent reduction in zinc.

“We are showing that global warming, climate change and particularly greenhouse gases – carbon dioxide – can have an impact on the nutrient content of plants we eat,” said co-author Adam Drewnowski, director of the UW’s Center for Public Health Nutrition and a professor of epidemiology.

CO2-induced changes in the nutritional quality of rice would likely “exacerbate the overall burden of disease and could affect early childhood development,” researchers said, noting that undernutrition can worsen diarrheal disease and malaria. CO2-induced nutritional deficits are projected to be greater for those countries with the lowest overall gross domestic product per capita, the study showed.

The research team included the Institute of Soil Science, Chinese Academy of Sciences; the University of Tokyo; the United States Department of Agriculture’s Agricultural Research Service; Bryan College of Health Sciences in Lincoln, Nebraska; and the University of Southern Queensland.