Introduction: The general US population is obsessed with dietary protein. Plant vs. animal food sources of dietary protein have been linked to differential environmental impacts. Current national dietary guidelines and published databases can be used to evaluate the impacts of shifts in the amount and type of protein intake in the US on the intersection of human and environmental health.

Methods: 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 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.

Results: 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 better 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.

Conclusion: Decreasing current US consumption of total protein, and shifting some protein intake from animal to plant food sources would have benefits for both human health and the environment.