Maximizing the intersection of human health and the health of the environment with regard to the amount and type of protein produced and consumed in the United States

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.

Keywords: Estimated Average Requirement; Recommended Dietary Allowance; animal-based protein; climate change; environment; greenhouse gases; plant-based protein; protein; sustainability; water.

Figure 1

Proportions of amino acids in selected foods across food groups. Amino acids are grouped as essential or nonessential, in descending order of prevalence within food groups. Amount of protein per 100 kcal is presented in Table S1. (Source: Nutrition Database System for Research, University of Minnesota; http://www.ncc.umn.edu/ndsr-database-page/). Abbreviations: Ala, alanine; Arg, arginine; Asp/n, aspartate and asparagine; Cys, cysteine; Glu/n, glutamate and glutamine; Gly, glycine; His, histidine; Iso, isoleucine; Leu, leucine; Lys, lysine; Met, methionine; Phe, phenylalanine; Pro, proline; Ser, serine; Thr, threonine; Trp, tryptophan; Tyr, tyrosine; Val, valine.

Figure 2

Carbon footprint of protein sources. Beef and lamb have by far the highest carbon footprint per unit of protein produced, followed by dairy, eggs, pork, and seafood. Plant proteins and poultry have the lowest carbon food prints per unit of protein. Detailed notes on the precise definitions of each category for each study and the exact studies included for comparison are listed in Table S2 in the Supporting Information online (Comparative Study 2 had values only for pork, poultry, and seafood). Abbreviation: KG CO2 eq, kilograms of carbon dioxide equivalents.

Figure 3

Blue water footprint (A) and green water footprint (B) of protein sources.^, Plant proteins have a higher water footprint than almost all animal proteins. The green water footprint of beef and lamb is even higher than plant proteins. Poultry and eggs have a particularly low overall water footprint. Detailed notes on the precise definitions of each category are listed in Table S3 in the Supporting Information online.

Figure 4

A day’s worth of protein on 1 plate. Each plate represents a different option for consuming 90 g or 67.5 g of protein for the entire day; ie, breakfast, lunch, dinner, and snacks combined. For ease of comparison, the same 3 animal foods (chicken, eggs, yogurt) and the same 3 plant foods (bread, peanuts, kidney beans) are used. Calories for each plate range from ≈ 600 kcal to ≈ 1000 kcal, suggesting these would represent 25% to 50% of total kilocalories for a 2000-kcal diet (and a smaller percentage for higher kilocalorie intake). Only protein-rich foods are pictured here (ie, no vegetables or fruits). Notably, as described previously, since all whole foods contain protein, the additional foods consumed would provide additional protein to a complete diet of ≥ 2000 kcal.

Figure 5

Calculations for carbon footprint (A) and water footprint (B) under different protein consumption scenarios. Abbreviation: KG CO2 eq, kilograms of carbon dioxide equivalents.