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Rice Becomes Less Nutritious as CO2 Levels Rise

25 May 2018

For the first time, research reveals that vitamins B1, B2, B5 and B9, all of which are important to the body's ability to turn food into energy, decrease in rice as carbon dioxide levels increased. The drop in the nutritional value of rice could mean it would be a disaster for the health and development of the two billion people who rely on rice as their primary source of nourishment.

Rice grown at higher carbon dioxide (CO2) concentrations, like those possible later this century, has lower nutritional value, according to a study that evaluated rice grown in Japan and China under simulated carbon dioxide increases.

Regardless of rice paddy location, all crops grown in higher CO2 environments were less nutritious: "containing about 10 per cent less protein, 8 per cent less iron and 5 per cent less zinc than rice grown under current levels of carbon dioxide", The Guardian reports.

With further research, scientists might try to breed or genetically engineer new crop varieties that preserve much of their nutritional value in the face of rising carbon dioxide.

"Anything that impacts rice in terms of its nutritional quality is going to have an impact", Lewis H. Ziska, study co-author and plant physiologist at the United States Department of Agriculture, told The Guardian. Plants that share the same photosynthesis pathway as rice and wheat do indeed grow larger and produce greater yields in higher carbon dioxide concentrations by creating more carbohydrates, says Lisa Ainsworth, a biologist at the University of IL at Urbana-Champaign and the U.S. Department of. The research also confirmed previously discovered declines in protein, iron and zinc.

They looked at 18 varieties of rice in total and analyzed half of them in China for levels of B vitamins like thiamine, riboflavin and folate (B1, B2, and B9).

Plants thrive thanks to carbon dioxide, as they use it for photosynthesis and then produce oxygen. The researchers suggested that changes in B vitamins may relate to the decline of nitrogen in plants exposed to elevated carbon concentrations.

Some varieties of rice may not experience as severe of a nutrient loss as carbon dioxide levels go up.

The declines in nutrition raise an obvious concern for public health, especially when observed in global staple crops like rice.

The new study took a more economic approach. They found that people in countries with lower GDP per capita, where rice may make up a greater proportion of their daily diet, are likely to be hit hardest.

"This paper draws on the data they've produced to show there's a detrimental effect on the quality of the rice grain in high CO2". Research also is needed to identify options to reduce or negate the risks, including studies to understand whether traditional breeding or genetic modification could lead to nutritionally superior rice, and understanding whether the nutritional quality of rice could be improved through the application of mineral fertilizers or post-harvest fortification.

In the meantime, Ziska hopes to investigate how crop nutrient contents may have already changed in previous decades, in response to historical greenhouse gases emissions.

"Trying to understand those complexities and trying to understand those interactions is one of the things we think is very important", he said.

Rice Becomes Less Nutritious as CO2 Levels Rise