TAMPA, Florida: As carbon dioxide rises due to the burning of fossil fuels, rice will lose some of its protein and vitamin content, putting millions of people at risk of malnutrition, scientists warned on Wednesday (Thursday in Manila).
The change could be particularly dire in Southeast Asia where rice is a major part of the daily diet, said the report in the journal Science Advances.
“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, a professor of epidemiology at the University of Washington.
Protein and vitamin deficiencies can lead to growth-stunting, birth defects, diarrhea, infections and early death.
Countries at most risk include those that consume the most rice and have the lowest gross domestic product (GDP), such as Myanmar, Laos and Cambodia, Drewnowksi said.
The findings were based on field studies in Japan and China, simulating the amount of CO2 expected in the atmosphere by the second half of this century – 568 to 590 parts per million. Current levels are just over 400 ppm.
For the experiments, 18 different strains of rice were planted in open fields, surrounded in certain areas by 56-foot wide (17-meter) octagons of plastic piping that released extra CO2.
According to study co-author Kazuhiko Kobayashi, a professor at the University of Tokyo, the experiment is designed to be more accurate than growing in a greenhouse.
Researchers found that iron, zinc, protein, and vitamins B1, B2, B5, and B9 – which help the body convert food to energy – were all reduced in the rice grown under higher CO2 conditions.
“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,” said the report.
On average, protein content fell 10.3 percent, iron dropped eight percent and zinc was reduced by 5.1 percent, compared to rice grown today under current CO2 conditions.
Vitamin B6 and calcium were unaffected, and vitamin E levels rose for most strains.
The reasons for the changes have to do with how higher CO2 affects the plant’s structure and growth, increasing carbohydrate content and reducing protein and minerals, said the study.
Higher CO2 means less exposure to nitrogen, which also may affect vitamin content, researchers said.