ARE HIGH PROTEIN DIETS LINKED TO HEART DISEASE?

High protein diets have become a popular weight lose strategy for many but animal studies and larger epidemiological studies in humans have indicted that they are a risk factor in cardiovascular disease. A recent mice study by researchers at Washington University School of Medicine¹, are now able to explain why a high protein diet may contribute to heart disease due to its impact on arterial plaques. In this article, I will review the findings in this study and suggest how making small adaptations to your diet, may help to protect against heart issues.

What is an arterial plaque?

Arterial plaques contain a mix of cholesterol, calcium deposits, fat and dead cells. An immune cell, called a macrophage, has an important role in cleaning up dead cells and toxic waste from the plaque so that it stays stable and doesn’t build up in size. A plaque is embedded in the arterial wall so as it grows it can cause blockages in the artery preventing blood flow and increasing blood pressure. A plaque can also become unstable if the immune cells – macrophages – don’t clean up properly which can lead to the artery bursting causing a heart attack.

So how is a high protein diet linked to an increased risk of a cardiac event?

The study by Zhung and co., found that in a high protein and high fat diet the arterial plaques not only grew, but they also became instable. The study compared this to mice on a low protein and high fat diet and although these mice gained weight, their plaques were not affected.

This is a noteworthy observation, as the mice on the high protein diet didn’t gain weight but did show an increased risk of cardiovascular disease. As such, those on a high protein diet should be cautious as even though it can lead to weight loss, it may have a negative impact on your heart health. A couple of scoops of protein powder in your daily smoothie can amount to 40 grams of protein which is almost the recommended daily allowance so tracking protein consumption is key for those with an increased risk of heart disease.

How does high protein affect the stability of arterial plaques?

The research also explains why protein has an impact on the stability and size of plaques, due to its effects on a protein found in macrophages called mTOR. When proteins are consumed in excess and broken down into their constituent elements called amino acids,  mTOR is activated.  In this process, the macrophage ceases its cleaning duties, and begins to grow. This encourages toxicity to build around the plaque, and through a chain of events the macrophages die, and these dead cells become part of the core of the plaque increasing its instability.

Interestingly, the study found that certain amino acids are more potent at activating mTOR, including leucine and arginine. Leucine is found in red meat, so protein consumed from fish and plants might be a better source of protein for those at risk of heart issues.

What is next for this area of research?

This is a fascinating new concept, which may help to develop therapies to prevent plaques building up in arteries and becoming unstable. Further research should look to understand which amino acids are implicated in mTOR so that dietary approaches can be adopted to ensure that the risk of cardiac events from plaques is minimised.

Do you have heart issues or have an increased risk of cardiovascular disease based on family history? If so, please do get in touch with The Autoimmunity Nutritionist clinic as we offer many dietary and lifestyle protocols to support health and circulatory health.

Xiangyu Zhang, Ismail Sergin, Trent D. Evans, Se-Jin Jeong, Astrid Rodriguez-Velez, Divya Kapoor, Sunny Chen, Eric Song, Karyn B. Holloway, Jan R. Crowley, Slava Epelman, Conrad C. Weihl, Abhinav Diwan, Daping Fan, Bettina Mittendorfer, Nathan O. Stitziel, Joel D. Schilling, Irfan J. Lodhi, Babak Razani. High-protein diets increase cardiovascular risk by activating macrophage mTOR to suppress mitophagy. Nature Metabolism, 2020; 2 (1): 110 DOI: 10.1038/s42255-019-0162-4