Eating Too Much Protein Makes Pee a Problem Pollutant in the U.S.

Scientific American ^

[FarCenter]

In the U.S., people eat more protein than they need to. And though it might not be bad for human health, this excess does pose a problem for the country’s waterways. The nation’s wastewater is laden with the leftovers from protein digestion: nitrogen compounds that can feed toxic algal blooms and pollute the air and drinking water. This source of nitrogen pollution even rivals that from fertilizers washed off of fields growing food crops, new research suggests.

When we overconsume protein—whether it comes from lentils, supplements or steak—our body breaks the excess down into urea, a nitrogen-containing compound that exits the body via urine and ultimately ends up in sewage. Maya Almaraz, a biogeochemist at the University of California, Davis, and her colleagues wanted to see how much of this nitrogen is being flushed into the U.S. sewage system because of a protein-heavy diet. The researchers combined population data and previous work on how much excess protein the average American eats and found that the majority of nitrogen pollution present in wastewater—some 67 to 100 percent—is a by-product of what people consume. “We think a lot about sewage nitrogen. We know that’s an issue,” Almaraz says. “But I didn’t know how much of that is actually affected by the choices we’re making way upstream—when we go the grocery store, when we cook a meal and what we end up putting in our bodies.”

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Their new study, published in Frontiers in Ecology and the Environment, broke down protein requirements by age (adults 50 to 70 years old need the most) for the current U.S. population and projected future populations out to 2055. By midcentury, the country’s population is expected to be larger overall and to have a greater percentage of older people. The researchers calculated the amount of nitrogen that would enter the environment if people ate today’s average American diet and if they instead reduced their protein intake to only what is nutritionally needed. This shift in diet alone could reduce the amount of nitrogen reaching aquatic ecosystems by 12 percent today and by nearly 30 percent in the future, according to the study’s results. Such a change could also help reduce damaging nitrogen pollution while wastewater infrastructure catches up.

[Verginius Rufus]

Pee in the bushes and save the planet!