Consuming protein is essential for human health, but we’re overdoing it, and it’s starting to negatively affect the environment, according to a new study.

Protein is found in muscle, bone, skin, hair and pretty much every part of the human body. Not getting enough protein in our diets, through eating animal- and plant-based foods, can lead to growth failure, muscle mass loss, decreased immunity, and weakening of the heart and respiratory system.

But Americans are overconsuming protein, and it’s now causing a problem for the country’s waterways.

An international group of researchers from the U.S., Australia and the United Kingdom have found that protein-packed diets are causing people to expel nitrogen-laden urine into U.S. sewer systems at levels that are causing a cascade of effects, including increased harmful algal blooms and aquatic “dead zones.”

The researchers found that reducing the intake of protein to only what was nutritionally needed could reduce the amount of nitrogen in waterways by 12% today and 30% by the year 2055.

The National Academy of Medicine recommends people get a minimum of 7 grams of protein for every 20 pounds of body weight, or about 60 grams of protein for people weighing 170 pounds and about 70 grams of protein for people weighting 200 pounds.

“We think a lot about sewage nitrogen. We know that’s an issue,” Maya Almaraz, study researcher and environmental scientist at the University of California-Davis told Scientific American. “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.”