As CO2 increases, rice loses B vitamins and other nutrients

By the end of this century, rice may not deliver the same B vitamin levels that it does today. Protein and certain minerals will dwindle, too, new data suggest.

Testing higher carbon dioxide concentrations in experimental rice paddies in China predicts losses in four vitamins — B1, B2, B5 and B9 — an international team reports May 23 in Science Advances. Adding results from similar experiments in Japan, the researchers also note an average 10.3 percent decline in protein, an 8 percent fall in iron and a 5.1 percent fall in zinc, supporting previous studies of rice and other crops (SN: 4/1/17, p. 14). Two bright spots: Vitamin B6 levels remained unchanged and vitamin E increased.
In experimental setups nicknamed FACE (free-air CO₂ enrichment) in China’s Yangtze River delta and near the Japanese city of Tsukuba, researchers grew a total of 18 varieties of rice. Piping exposed the rice to CO2­ concentrations elevated to 568 to 590 parts per million — higher than the current level of 410 ppm, but in line with the current trend toward 570 ppm in this century.

The nine rice varieties from China, from three years’ crops and analyzed in their unrefined brown form, differed in degree of vitamin loss. On average, B1 levels (thiamine) declined 17.1 percent; B2 levels (riboflavin), 16.6 percent; B5 (pantothenic acid), 12.7 percent; and B9 (folate), 30.3 percent.

Such declines in rice nutrients could hit economically strapped populations in Asia the hardest. Nine of the world’s 10 most rice-dependent countries are in Asia. (The other is Madagascar.) The researchers predict that about 600 million people currently without good options for switching diets could risk nutrient deficiencies from rice declines. B vitamins help with a range of bodily tasks, from maintaining a healthy brain to enabling normal fetal development.