Abstract
This review utilizes current national dietary guidelines and published databases to evaluate the impacts of reasonable shifts in the amount and type of protein intake in the United States on the intersection of human and environmental health. The established scientific basis and recommendations for protein intake as described in the US Dietary Reference Intakes are reviewed. Data on food availability from both the US Department of Agriculture and the Food and Agriculture Organization of the United Nations and data on consumption from the National Health and Nutrition Examination Survey are used to examine estimates of current US protein consumption. Greenhouse gas (carbon dioxide equivalents, CO2eq) and blue and green water impacts of US protein consumption resulting from US agricultural practices were obtained from previously published meta-analyses. A 25% decrease in protein intake paired with a 25% shift from animal food to plant food protein intake-from an 85:15 ratio to a 60:40 ratio-would best align protein intake with national dietary recommendations while simultaneously resulting in 40% fewer CO2eq emissions and 10% less consumptive water use. The modeling of this strategy suggests a savings of 129 billion kilograms of CO2eq and 3.1 trillion gallons of water relative to current consumption.