The Latest Protein Panic
If you're going to eat protein, have a steak not a "liquid protein meal"...
A couple of weeks ago a study on protein consumption was published in nature metabolism, concluding that their data demonstrated a mechanistic basis for the adverse impact of excessive dietary protein on cardiovascular risk.1 I first came across this study on Twitter / X, as it got a lot of negative feedback and quite the attention (the tweet below hit 10+ M views).
But before we delve into the controversy, just to outline the study aims, as its name is a bit intimidating for the non-science / medical people; “Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk”.
So, let’s break this title down first:
Leucine is an essential amino acid, all proteins are made up of 20 different amino acids, of which 9 are considered essential (leucine is one of the 9), and the rest non-essential. The 9 are known are essential as our body cannot make those on its own or cannot produce adequate amount of it, the non-essential ones can be produced by our body from other compounds.
Macrophage mTOR signalling - macrophages are a type of white blood cells that play a role in the immune system, mTOR signalling is a pathway that cells use to regulate growth, proliferation, mobility, and survival. So in this case it is the pathway within those white blood cells.
Threshold effect refers to the presence of a factor (leucine in this study) above a specific level (threshold) means an effect (in this case macrophage mTOR signalling) is observed.
In simple terms, it’s looking at how leucine influences macrophages / immune cells and the pathway, and in turn how that may affect to cardiovascular risk / heart health.
This study reports two clinical trials, of 23 men and women participating in them. They had the typical medical history, physical examination, fasted blood tests. The participants were split into a very-high-protein liquid-meal study with 14 participants (study 1) and the high-protein mixed-meal study with 9 participants (study 2).
In study 1, they had two 500 calorie liquid meal after an overnight fast and within 5 mins of their blood test. Then they took more blood 1h and 3h post consumption.
Now, from the get-go this sounds a bit dodgy, as if I were to think of a high protein meal (a) it would not be a liquid, and (b) it would probably be a steak. This “meal” was made using Boost Plus (nutrition supplement beverage), Unjury (protein isolate product), non-fat dry milk powder, Sol Carb (nutritional carbohydrate polymer - is this even food?), canola oil and water. This meal meant 50% of cals were from protein, 17% from fat, and 33% from carbs.
In my very humble opinion, this is not even actual food to begin with, and not even a good high protein meal. This just is more proof of how badly nutrition diets are done, as in reality no person would be consuming these on the daily as a standard meal.
You can see the ingredient of Boost from the tweet above, and outside that is it classified as UPF (see Chris van Tuleken on ultra-processed food). It’s mostly a highly inflammatory mix of glucose syrup and canola oil - sounds delicious and a great protein source…
Study 2, contained what they called “real” food (see screenshot below) - which would be something probably consumed by an average person. In this case the extra protein was from adding animal protein isolates (egg, chicken, beef and whey). But before you think oh this sounds like an improvement, this meal had no actual egg, chicken or beef in it; they extracted and isolated the protein form the chicken which would produce a protein powder.
I won’t go into the biomechanics, as you can also read it in the paper, but they do have this pretty graph that shows the relationship of protein intake with respect to cardiovascular risk, the mTOR activation in macrophages, and leukocytes (Leu).
So, their end all conclusion was that if people were to blindly increase protein intake they would naturally put themselves at a higher risk of cardiovascular disease. But, firstly, this is not really translatable as no person would be standardly consuming these “meals” they created, unless they teach them how to isolate proteins themselves and also drink these lovely liquid meals. The more logical thing to conclude and also translate to people, is that the whole diet should be address as a whole. If having a balanced diet and meals, having a bit more protein probably won’t increase your cardiovascular disease by that much. Again, also the type of protein people are consuming plays a role for many reasons, if you compare hot dogs to chicken breast, I think it is pretty clear the downside of the former. Say salmon, high in omega 3s, selenium how can you compare that to the liquid protein?
To wrap up, my two cents are don’t believe each headline you read especially when it comes to nutrition relating studies. A balanced and diet rich in many different types of food is probably your best bet at decreasing disease of any sort, rather than extreme diets, whether that is carnivore, vegan, keto etc.
To close off, I’ll use Greek philosopher’s, Kleovoulos o Lindios, phrase “Metron Ariston” which translates to “Everything in Moderation”.
As usual, I’ve added some links below. I hope you enjoyed - see you next week! :)
Zhang, X., Kapoor, D., Jeong, SJ. et al. Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk. Nat Metab 6, 359–377 (2024). https://doi.org/10.1038/s42255-024-00984-2