Alarming study warns too much protein can lead to heart disease

PITTSBURGH — High-protein diets are viewed as essential for athletes, bodybuilders, or individuals just trying to improve muscle mass and strength. A new study, however, is making us rethink the health benefits of eating too much protein. University of Pittsburgh School of Medicine scientists reveal that excess protein in the diet is bad for the heart.

The findings provide compelling evidence that these particular diets, including those exceeding 22 percent of daily caloric intake from protein, can escalate the risk of atherosclerosis, a condition characterized by the hardening and narrowing of arteries due to plaque buildup.

Researchers embarked on a comprehensive investigation combining human trials with animal and cellular studies. The study reveals a complex molecular mechanism whereby high protein consumption leads to increased activation of immune cells implicated in the formation of atherosclerotic plaque, thereby elevating the risk of heart disease.

“Our study shows that dialing up your protein intake in pursuit of better metabolic health is not a panacea. You could be doing real damage to your arteries,” says senior and co-corresponding study author Dr. Babak Razani, professor of cardiology at the University of Pittsburgh, in a university release. “Our hope is that this research starts a conversation about ways of modifying diets in a precise manner that can influence body function at a molecular level and dampen disease risks.”

A critical aspect of this study is the identification of leucine, an amino acid predominantly found in animal-based foods such as beef, eggs, and milk, as a key player in promoting the pathways associated with atherosclerosis. This discovery sheds light on the specific components of protein-rich diets that may contribute to cardiovascular risk, opening avenues for more targeted nutritional strategies or “precision nutrition” to mitigate disease risk.

The context for this research is the growing popularity of high-protein diets, driven by widespread beliefs in their health benefits, including muscle maintenance and weight loss. However, this study challenges the notion that more protein is invariably better, suggesting that over-reliance on protein, especially from animal sources, may have unintended health consequences.

For the study, researchers conducted a series of experiments to explore how amino acids from protein influence disease processes at the molecular level. Particularly, they focused on macrophages, immune cells in the blood vessels that play a crucial role in the development of atherosclerosis. The research demonstrated that high dietary protein intake could disrupt the normal function of these cells, leading to the accumulation of cellular debris within the arterial walls and exacerbating plaque formation.

“We have shown in our mechanistic studies that amino acids, which are really the building blocks of the protein, can trigger disease through specific signaling mechanisms and then also alter the metabolism of these cells,” notes Dr. Bettina Mittendorfer, a metabolism expert at the University of Missouri. “For instance, small immune cells in the vasculature called macrophages can trigger the development of atherosclerosis.”

This study not only contributes to our understanding of the dietary factors influencing cardiovascular health but also raises important questions about the optimal protein intake for maintaining heart health without triggering adverse effects. Researchers highlight a critical gap in knowledge regarding the effects of protein consumption within the recommended dietary range and the potential for optimizing protein intake to leverage its benefits while minimizing risks.

The implications of these findings are particularly relevant in clinical settings, where high-protein diets are often prescribed to support recovery and muscle mass preservation in severely ill patients.

“Perhaps blindly increasing protein load is wrong,” explains Dr. Razani. “Instead, it’s important to look at the diet as a whole and suggest balanced meals that won’t inadvertently exacerbate cardiovascular conditions, especially in people at risk of heart disease and vessel disorders.”

As the conversation around dietary guidelines continues to evolve, this study underscores the importance of considering the molecular impacts of diet on health. With cardiovascular diseases remaining a leading cause of mortality globally, the insights from this research could inform future nutritional recommendations, aiming for a balanced diet that supports overall health without compromising cardiovascular integrity.

The study is published in the journal Nature Metabolism.