Rising carbon dioxide levels from global warming will drastically reduce the amount of protein in staple crops like rice and wheat.
This will leaving vulnerable populations at risk of growth stunting and early death, experts have warned.
Researchers say they still don't understand how or why carbon dioxide emissions sap protein and other nutrients from plants.
An additional 150 million people globally may be at risk of protein deficiency by 2050 because of rising levels of carbon dioxide in the atmosphere, however.
Rising carbon dioxide levels from global warming will drastically reduce the amount of protein in staple crops like rice and wheat. This image shows Indian farmers plant paddy seedlings in a rice field on the outskirts of Amritsar
Researchers calculated that by 2050, higher CO2 concentrations will sap the protein contents of barley by 14.6 percent, rice by 7.6 percent, wheat by 7.8 percent, and potatoes by 6.4 percent.
A full 76 percent of the people on Earth rely on plants for most of their daily protein, particularly in poor areas of the globe.
The hardest hit areas are expected to be Sub-Saharan Africa, where millions already don't get enough protein in their diets, and South Asia where rice and wheat are common staples.
India alone may lose 5.3 percent of protein from a standard diet, putting a predicted 53 million people at new risk of protein deficiency.
Researchers said solutions may include cutting carbon emissions, supporting more diverse diets, enriching the nutritional content of staple crops, and breeding crops that are less sensitive to the harmful effects of CO2.
The study, led by Harvard University, is the first to quantify the impacts of global warming on the protein levels of crops.
It relies on data from open field experiments in which plants were exposed to high concentrations of CO2.
Global dietary information from the United Nations was used to calculate the impact on people who live dangerously close to the edge when it comes to getting enough protein.
Without it, growth is stunted, diseases are more common