Rising levels of carbon dioxide (CO2) from human activity are making staple crops such as rice and wheat less nutritious and could result in 175 million people becoming zinc deficient and 122 million people becoming protein deficient by 2050, according to new research led by Harvard T.H. Chan School of Public Health. The study also found that more than 1 billion women and children could lose a large amount of their dietary iron intake, putting them at increased risk of anemia and other diseases.