February 21, 2024 — Scientists have found that consuming more than 22% of dietary calories from protein can reduce atherosclerosis (a disease on the walls of arteries) by activating immune cells involved in the process. The researchers found that this can lead to an increased risk of developing plaque, a buildup of fat, cholesterol, and other substances. . Recent clinical research suggests that the amino acid leucine plays an important role in promoting the formation of arterial plaque, which is responsible for the majority of heart attacks and strokes.

This negative effect of high protein on heart health is caused by activation of a signaling pathway (mTORC1) that is involved in the development of heart disease. The researchers conclude that leucine is a key activator of this pathway.

“Leucine is one of three branched-chain amino acids (BCAAs): leucine, isoleucine, and valine. There are 20 amino acids that are the building blocks of all proteins, including those we eat.” said lead author Babak Razani, MD, professor of cardiology at the University of Pittsburgh School of Medicine. nutrition insights.

“Ten amino acids, including the three BCAAs, are considered ‘essential’, meaning they must be obtained from the diet and are not synthesized in our bodies,” he explains.

“Many amino acids increase in the bloodstream after protein ingestion, which activates mTORC1 and a harmful signaling pathway in macrophages, immune cells that are a key factor in atherosclerosis (or cardiovascular disease). It is mainly leucine that becomes oxidized.

Although a high-protein diet is often promoted as part of a healthy lifestyle, researchers recommend that you carefully consider your high-protein intake. However, experts stress that further research is needed to validate the results in humans over a longer period of time.

Mechanism of immune cells
Regarding this research, natural metabolism, the team conducted experiments in cells, mice, and humans. The researchers determined the timeline of immune cell activation after ingesting a protein-rich diet in humans and simulated similar conditions in mice and macrophages.

The study authors compared the effects of liquid diets containing 10% or 50% of their energy as protein on mTORC1 activation in human participants. A second study evaluated these results in participants who consumed either a standard mixed protein diet or a mixed diet with moderate increases of 15% and 22% of calories. Did.

The researchers assessed participants’ plasma amino acid concentrations and mTORC1 signaling 1 to 3 hours after meal intake.

The research team determined the threshold concentration at which leucine promotes harmful mTORC1 signaling at blood concentrations between 100 μM and 300 μM. They found this concentration after a high protein diet (22% or 25g of energy as protein) and a very high protein diet (50% of energy).

The leucine threshold is set between 100 μM and 300 μM in the blood and occurs after ingesting 22% or 25 g of energy as protein.The researchers then confirmed that protein intake above this threshold caused atherosclerosis in mice with genetic abnormalities that made them more susceptible to the disease. The authors designed a diet with graded protein content that corresponded to the average and high protein intake of mice in the US population.

“Our study shows that increasing your protein intake to improve metabolic health is not a panacea; you may be doing significant damage to your arteries,” Labak said. say.

“We hope this study will spark a discussion about how to modify diet in precise ways that can affect body function at a molecular level and reduce the risk of disease.”

“Essential amino acids
A study published last year suggested that reducing the intake of the essential amino acid isoleucine (an isomer of leucine) could extend the lifespan of mice by 33% in males and 7% in females. The adapted diet made the mice leaner and more frail as they aged, and they had less cancer and prostate problems.

Babak commented that in the current study, levels of isoleucine were even higher than leucine after subjects consumed protein-rich smoothies and meals. But Roisin was the only bad guy.

“The data on isoleucine and its limitations are very interesting. The crux of that data is about protein limitation (specifically isoleucine limitation) in metabolic health and longevity, and it’s important to assess atherosclerosis and cardiovascular disease. “It wasn’t a thing,” he explains.

“This creates a situation where one BCAA (isoleucine, not leucine) may harm certain aspects of metabolic disease, while another BCAA (leucine, not isoleucine) causes problems in cardiovascular disease. I am doing it.”

“The deep insight here, which may not be fully understood yet, is that not all amino acids, or more precisely all branched-chain amino acids, are created equal. They has its own positive and negative aspects in our bodies.”

additional research required
At the same time, study authors and other experts note that further research is needed to study the effects of high-protein diets and leucine intake on humans. Additional clinical trials will be important to evaluate the effects of different amounts and types of protein on the identified signaling pathways to ensure correct dietary guidelines regarding protein intake.

“There are gaps in our knowledge that are leading to an exciting frontier in nutritional science, a kind of precision nutrition renaissance,” Babak emphasizes. “By understanding the mechanisms of how certain nutrients affect our cells and organs, we can advise on what foods and compositions we should consume to reduce the risk of disease. Masu.”

Further research is needed to examine the effects of high protein and different types of protein on humans.Dr. Duane Mellor, registered dietitian and senior lecturer at Aston University in the UK, also calls for careful interpretation of data that combine research data from different approaches.

“This study only shows changes in plasma levels and macrophage pathway activation after a single meal in humans. Therefore, the effects of daily food intake in humans are unknown from this study. Mice Although it is used as a model for human heart disease, there are subtle differences in normal dietary intake and metabolism.”

He also emphasized that the study does not show the effects of food on human consumption. The protein meals and shakes used are very different from what is considered a “healthy diet that includes protein from meat or fish and legumes, nuts, seeds, and cereals such as whole grain bread or pasta.”

animal protein and vegetable protein
The researchers also point to studies showing that high intakes of protein from plant sources may not cause adverse health effects.

For example, a study earlier this year found that women who eat more plant-based protein are more likely to develop fewer chronic diseases and be healthier overall as they age.

Tom Saunders, emeritus professor of nutrition and dietetics at King’s College London, comments that high intakes of vegetable protein and fat do not promote atherogenesis.

“Various amino acids such as methionine and BCAA (including leucine and isoleucine), which are abundant in animal proteins, are the main suspects. Leucine levels are particularly high in whey protein, which promotes muscle growth in pigs. is well known.”

At Yolanda Van Hal

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