According to a study by the University of California, Davis, balancing the amount of protein you eat with the amount your body needs can reduce nitrogen emissions to US water systems by 12% and total nitrogen losses to air and water by 4%.
The consumption of both plant and animal protein in the United States is among the highest in the world. A study published in the journal Frontiers in ecology and environmentsaid that if Americans ate protein in the recommended amounts, projected levels of nitrogen excretion in 2055 would be 27% lower than today, despite population growth.
The study is the first to assess how much protein consumption contributes to excess nitrogen in the environment through human waste. It also suggests that coastal cities have the greatest potential to reduce nitrogen emissions into their watersheds.
“It turns out that many of us don’t need as much protein as we eat, and that affects our health and aquatic ecosystems,” said lead author Maya Almaraz, a research fellow at UC Davis’ Institute for the Environment. “If we could reduce this to an amount appropriate for our health, we could better protect our environmental resources.”
The human body needs protein. But when the body takes in more protein than it needs, the excess amino acids break it down to nitrogen, which is excreted mainly in the urine and excreted through the sewage system. This brings additional nitrogen into waterways, which can lead to toxic algal blooms, oxygen-deficient “dead zones” and contamination of drinking water.
Scientists estimated current and future exports of nitrogen emissions based on US Census data. They saw an upward trend over time, with exports increasing by 20% from 2016 to 2055. This increase is due to population growth as well as an aging population that requires more protein to combat muscle loss.
Coastal cities have the greatest potential for reduction
Coastal cities will face dramatic population growth in the coming decades, and suburban migration patterns show that such movement is typically accompanied by increased nutrient loads carried by sewage, stormwater and other sources.
The study found that coastal cities along the West Coast, Texas, Florida, Chicago, and especially in the northeastern United States show great potential to reduce dietary nitrogen loads to their watersheds.
Runoff accounts for 15% of the total nitrogen flux from land to ocean in North America, the study found. Technology capable of removing 90% of nitrogen from wastewater exists, but less than 1% of wastewater is treated with it due to its cost. A diet that balances protein with the body’s needs can be healthier for humans and reduce nitrogen pollution without the added cost of wastewater treatment.
“It’s interesting to think about possible ways to reduce these nitrogen losses other than expensive technologies,” Almaraz said. “Changing your diet is a healthy and inexpensive way to do this.”
The study was co-authored by Caitlin Kuempel of the University of Queensland, Andrew Salter of the University of Nottingham and Benjamin Halpern of the University of California, Santa Barbara.
It was funded by the National Center for Ecological Analysis and Synthesis, the World Wildlife Fund, and the Rockefeller Foundation.