High-protein diets are more and more popular as a method to increase muscle mass and lose weight. New research shows that excessive consumption of protein-rich foods may damage heart health due to their high presence of specific amino acids.

Two sulfur amino acids are present in protein-rich food: methionine, an essential amino acid, and cysteine, a semi-essential amino acid. Although vital for the body to function, when present in excessive quantities, they may be harmful.

For their study, researchers from Penn State analyzed health and dietary information from 11,576 people taken by the Centers for Disease Control and Prevention. In particular, they examined tell-tale biomarkers, such as cholesterol, triglycerides, glucose, and insulin in each participant's blood after fasting for 10-16 hours. They also made calculations on each participant's nutrition intake from analyzing their diets.

After controlling results for body weight, the researchers found that, on average, each participant had almost 2.5 times the estimated average requirement of 15 milligrams per kilogram of body weight per day. Given the high levels of dairy and meat products found in the average American diet, this did not come as a surprise.

They also found that those with a higher sulfur amino acid intake also tended to have higher composite cardiometabolic risk scores. The correlations remained the same even after accounting for factors such as age, biological sex, and history of health conditions, including hypertension and diabetes.

The results suggest that diets with lower quantities of sulfur amino acids are more beneficial for heart health, such as those richer in plant-based products. The researchers caution, however, that their findings are so far only observational. Further research is thus needed, preferably via a longitudinal study.

Nevertheless, co-author of the study, Professor John Richie, said, "For decades, it has been understood that diets restricting sulfur amino acids were beneficial for longevity in animals. This study provides the first epidemiologic evidence that excessive dietary intake of sulfur amino acids may be related to chronic disease outcomes in humans."

Sources: Healthline, Medical News Today and CNN