Protein is an essential part of our diet and has been linked to multiple health benefits, including improving the speed of muscle recovery after exercise or injury and helping maintain a healthy weight by curbing appetite. However, research from the University of Pittsburgh School of Medicine suggests that eating too much protein could cause cardiovascular damage.
What is protein?
Protein is a macronutrient contained in certain foods and drinks. It is made up of chemicals called amino acids, which are broken down when consumed and digested. The body then builds all the different proteins it needs from these amino acids.
Are there health risks to eating too much protein?
According to a study, carried out by researchers at the University of Pittsburgh School of Medicine, high protein consumption could increase the risk of developing atherosclerosis by activating immune cells, which contribute to arterial plaque formation. Atherosclerosis is the build-up of fats, cholesterol and other substances in and on the artery walls. This build-up is called plaque and can cause arteries to narrow and block blood flow. The plaque can also burst, leading to a blood clot.
The study, which combined small human trials combined with experiments on mice and cells in a petri dish, showed that consuming over 22% of dietary calories from protein could lead to increased activation of immune cells that play a role in atherosclerotic plaque formation.
Furthermore, the scientists discovered that one particular amino acid, leucine, appeared to have a disproportionately high effect in driving the pathological pathways linked to atherosclerosis or hardened arteries.
What is leucine?
Leucine is one of the three essential branched chain amino acids, along with isoleucine, and valine. These amino acids can be used by skeletal muscle to give energy during exercise. Eating foods containing complete protein, such as meat, poultry, fish, eggs, and milk, provides these amino acids.
“Our study shows that dialling up your protein intake in pursuit of better metabolic health is not a panacea. You could be doing real damage to your arteries,” explained Babak Razani, professor of cardiology at the University of Pittsburgh School of Medicine. “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.”
This study, titled ‘Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk’ follows a previous study by the team which first identified excessive protein consumption as a potential cause of atherosclerosis. This next study, conducted in collaboration with Dr Bettina Mittendorfer, a metabolism expert at the University of Missouri, was therefore designed to delve deeper into the potential risk.
“We have shown in our mechanistic studies that amino acids, which are really the building blocks of the protein, can trigger disease through specific signalling mechanisms and then also alter the metabolism of these cells,” added Dr Mittendorfer. “For instance, small immune cells in the vasculature called macrophages can trigger the development of atherosclerosis.”
The research team were careful to note that further research on the subject is required as many questions remain unanswered, primarily, what is the correct amount of protein to consume each day without risking adverse health effects and what sources of protein are most likely to trigger these adverse health effects.
What is atherosclerotic plaque formation?
Atherosclerosis is the thickening or hardening of the arteries within the human body. It is caused by a build-up of plaque in the inner lining of an artery. Plaque is made up of deposits of fatty substances, cholesterol, cellular waste products, calcium, and fibrin. As it builds up in the arteries, the artery walls become thickened and stiff.
What are the health benefits of eating protein?
Protein is not just beneficial to our health, it is an essential part of our diet, supporting a multitude of functions. It is essential for the growth and repair of body tissues and is especially important for healthy muscles and bones, particularly in children.
According to the British Nutrition Foundation, “there are thousands of different proteins in the body that have a huge variety of roles, in our organs like our brain, heart and liver, the antibodies in our immune system and the haemoglobin that carries oxygen in our blood. Protein is important for children’s muscles and bones as they are growing, and also to keep our muscles and bones healthy throughout life.” Furthermore, British Nutrition Foundation states that “protein is relatively ubiquitous in the food system so a diet which is deficient in protein is also likely to be deficient in other nutrients such as vitamins and minerals.”
How much protein should we consume?
According to the British Heart Foundation, the current recommended daily intake of protein is 55 grams per day for men and 45 grams per day for women. This is based on bodyweights of 75kg for men and 60kg for women.
Protein can be consumed in various forms, including meat, fish, eggs, dairy, nuts, beans and pulses.
Source: Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk
Published online: 19 February 2024
DOI: https://www.nature.com/articles/s42255-024-00984-2
Authors: Xiangyu Zhang, Divya Kapoor, Se-Jin Jeong et al.