WASHINGTON, May 23 (Xinhua) -- A study published on Wednesday in the journal Science Advances showed that increased carbon dioxide was linked to less nutritional value of rice, including vitamins and protein.
An international research team revealed that rice grown at concentrations of atmospheric carbon dioxide expected by the end of this century would have lower levels of four key B vitamins.
The findings also supported previous research showing rice grown under higher carbon concentrations had less protein, iron and zinc.
The researchers from Australia, China, Japan and the United States conducted the field study on 18 common strains of rice.
They built a 17-meter-wide plastic pipe octagons elevated about 30 centimeters above the tops of plants within standard rice fields, with sensors and monitors measuring how much carbon dioxide is released out of the pipes designed to raise the carbon concentration to a desired experimental level.
The findings revealed average declines in vitamins B1, B2, B5 and B9, vitamins essential to helping the body convert food into energy, under a scenario of carbon concentration the scientists expect by the end of this century.
Average Vitamin B1 levels decreased by 17.1 percent; average Vitamin B2 by 16.6 percent; average Vitamin B5 by 12.7 percent; and average Vitamin B9 by 30.3 percent, according to the study.
The researchers reported no change in levels of Vitamin B6 or calcium, while Vitamin E levels increased for most strains.
Also, they reported an average 10.3 percent reduction in protein, 8 percent reduction in iron and 5.1 percent reduction in zinc, when compared with rice grown under current carbon concentrations.
Some studies have noted that higher levels of carbon dioxide spur plant growth through increased photosynthesis. The researchers suggested that changes in B vitamins may relate to the decline of nitrogen in plants exposed to elevated carbon concentrations.
The nutritional deficits are likely to hit hard in countries where rice makes up a major portion of daily diets. About 600 million people, mostly in Southeast Asia, get more than half of their daily calories and protein directly from rice.
Researchers said those changes in the nutritional quality of rice would likely exacerbate the overall burden of disease and could affect early childhood development. Also, the undernutrition can worsen diarrheal disease and malaria.