It has been touted for its muscle-building and appetite-suppressing qualities, but scientists fear the protein may be bad for your arteries.
Researchers at the University of Pittsburgh found that mice fed diets rich in macronutrients had dangerous levels of plaque linked to strokes and heart attacks.
They suggested that this had been caused by high levels of proteins causing dysfunction in the immune system, causing white blood cells to build up within the walls of the arteries and leading to the build-up of fatty deposits.
It comes as high-protein diets are at the peak of popularity, which has been linked to the rise of gym culture.
Dr Babak Razani, a cardiologist who led the research, warned that his study suggested that “increasing” protein intake was “not a panacea” (file image)
Dr Babak Razani, a cardiologist who led the research, warned that his study suggested that “increasing” protein intake was “not a panacea” for a good diet.
He suggested that people should instead make sure they eat a “balanced” diet that contains enough carbohydrates, fats and vital nutrients.
Americans are recommended to eat about 0.36 grams (g) of protein per pound of body weight per day.
For an average man weighing 199 pounds, this is about 71 g per day, equivalent to two chicken breasts or one and a half fillets of salmon.
And for an average woman weighing 170 pounds, this equates to 61.2 g per day, which is equivalent to one and a half steaks of tuna or two cups of chickpeas.
But gym culture promotes consuming much more, and some plans suggest doubling this amount, or about 0.8 g per pound of body weight per day.
Once consumed, protein is broken down into amino acids that are used to repair torn muscle fibers and help grow new ones.
But if someone does not exercise, unused proteins are filtered from the body by the kidneys and excreted through urine. The body cannot store protein.
In his theory, revealed in the magazine. nature metabolismScientists warned that a high level of protein in the diet could activate macrophages, a type of white blood cell responsible for removing cellular waste.
However, they suggested that these activated cells would not function properly and would instead accumulate in “cemeteries” within the walls of the arteries.
Their study, which involved giving humans a protein shake and mice a high-protein diet, showed that after consuming these meals, levels of an amino acid, leucine, increase in the bloodstream.
This stimulated white blood cells and caused inflammation, they said, which could lead to plaque formation.
Dr. Bettina Mittendorfer, a metabolism expert at the University of Missouri who was also involved in the research, said: “We have shown in our mechanistic studies that amino acids, which are actually the building blocks of protein, can trigger diseases at through specific signals. mechanisms and then also alter the metabolism of these cells.’
“For example, small immune cells in the vasculature called macrophages can trigger the development of atherosclerosis.”
Dr. Razani added: “Perhaps blindly increasing protein loading is wrong.” [especially in hospital patients].
“Instead, it is important to look at the diet as a whole and suggest balanced meals that do not inadvertently exacerbate cardiovascular conditions, especially in people at risk for heart disease and vascular disorders.”
Limitations of the study include that it has only been carried out in mice and for a short period, and the research now needs to be repeated in humans.
It’s also unclear whether other factors, such as stress and other dietary substances, could have driven plaque buildup.
Dr Robert Storey, a cardiologist at the University of Sheffield, UK, who was not involved in the paper, said: “This research provides evidence that a high-protein diet may trigger responses in the body that contribute to heart attack risk. or stroke as a result of a particular protein component that is present in higher quantities in animal protein compared to plant proteins.
‘We know that most heart attacks and strokes are caused by the buildup of fat in the blood vessels that supply the heart and brain.
“They also show that leucine is the protein component that increases redness in the arteries when administered to mice.”