Global Health Implications of Nutrient Changes in Rice Under High Atmospheric Carbon Dioxide

A growing literature has documented that rising concentrations of carbon dioxide in the atmosphere threaten to reduce the iron, zinc, and protein content of staple food crops including rice, wheat, barley, legumes, maize, and potatoes, potentially creating or worsening global nutritional deficiencies for over a billion people worldwide. A recent study extended these previous nutrient analyses to include B vitamins and showed that, in rice alone, the average loss of major B vitamins (thiamin, riboflavin, and folate) was shown to be 17-30% when grown under higher CO₂. Here, we employ the EAR cut-point method, using estimates of national-level nutrient supplies and requirements, to estimate how B vitamin dietary adequacy may be affected by the CO₂-induced loss of nutrients from rice only. Furthermore, we use the global burden of disease comparative risk assessment framework to quantify one small portion of the health burden related to rising deficiency: a higher likelihood of neural tube defects for folate-deficient mothers. We find that, as a result of this effect alone, risk of folate deficiency could rise by 1.5 percentage points (95% confidence interval: 0.6-2.6), corresponding to 132 million (57-239 million) people. Risk of thiamin deficiency could rise by 0.7 points (0.3-1.1) or 67 million people (30-110 million), and riboflavin deficiency by 0.4 points (0.2-0.6) or 40 million people (22-59 million). Because elevated CO₂ concentrations are likely to reduce B vitamins in other crops beyond rice, our findings likely represent an underestimate of the impact of anthropogenic CO₂ emissions on sufficiency of B vitamin intake.