A recent article published in Nature Metabolism entitled “High-protein diets increase cardiovascular risk by activating macrophage mTOR to suppress mitophagy” raises suspicion regarding high protein diets’ connection to atherosclerotic plaque initiation and formation. What is particularly interesting about this study is that the mechanism – not just the association – by which the protein causes these plaques to form is determined and elucidated. Despite the study being performed on mice, identifying the mechanism makes this study stand out because in identifying the mechanism rather than simply the association, the “conclusions” may be more reasonably and likely transferred to humans. Researchers found that, when protein intake was 43% of total caloric intake, and, the remaining calories included some fats (as is typical in all Western diets and most any diet), certain immune cells called macrophages were destroyed (apoptosis). This process not only leads to the formation of plaque, but the worst kind (yes, there are some kinds worse than others). Plaques that include more “complexity” and a higher “necrotic burden” are the type that tend to create more problems – the “soft” or “fibrous” plaques that can be released to form blockages resulting in stroke and myocardial infarction (heart attacks).
So, yet another “diet” is actually bad for you? “High-carb” makes you fat, “ketogenic” is unsustainable, and now “high-protein” will give you a stroke or heart attack? No….
First of all, despite the way it sounds presented in medical literature and popular press, one particular diet does not fit all. Individual differences in genetics, age, health, season, daily activity, stress, and goals (to name but a few) must all be considered in designing one’s diet/nutrition. That said, certain popular “diets” can be a starting point in designing one’s individual diet plan. E.g., if you have a predisposition for a stroke, then we know that the “Mediterranean Diet” has been shown to reduce the average person’s* relative risk** of stroke by a significant percentage. Good place to start, right? But, what if this person with a predisposition for stroke is also very active, overweight (read, “fat”), and his trade requires him to carry as much muscle as possible? For him to maintain his activity level, lose fat, and carry enough muscle for his trade, it would be very hard (not impossible) for many in his position to avoid relatively high amounts of leucine-rich (typically animal) protein and (therefore) saturated fat (except for protein from fish). But, if high protein (particularly leucine-rich) diets increase risk of plaque build-up – the kind that most often breaks off to cause stroke – then what does he do? Of course, just being fat is a health problem typically in and of itself so, at least for the short term (until optimal body composition is restored), a high protein diet may be a great idea. Is he going to die of a stroke then? Not very likely. Why? The individual differences aside, a high-protein diet can be used in the short term to decrease fat and increase muscle (assuming as always that he is training and sleeping right as well) without significantly, if at all, increasing his risk for stroke. In fact, while on the high protein diet he could utilize other methods to reduce his inflammatory burden, e.g., by keeping his antioxidant levels higher (eating his veggies) and keeping other stressors low (e.g. getting enough sleep) or taking supplements like curcumin, Boswelia or omega-3 rich fats. He could also lower the other risk factors such as LDL (“bad”) cholesterol by taking red yeast rice and taking niacin to lower triglycerides and raise HDL (“good”) cholesterol. Once he reaches his desired body composition, he could begin incorporating more less protein-rich foods or even just reduce higher-leucine content foods (replacing animal protein with vegetable sources) in order to then maintain, rather than change, body composition. Of course, one can also always make sure everything is safe by monitoring the vasculature with imaging rather than make guesses based upon the so-called risk factors. Sound confusing or even Byzantine? It is. Because there are so many factors involved in determining the optimal diet. That’s why general “diets” can be so misleading and sometimes useless or even harmful without weighing in (pun intended) with all the considerations mentioned above.
So, again, the most recent study may be a clue, but certainly not yet conclusive. And, while I would not necessarily recommend a high-protein diet to the general populace as a long-term nutrition strategy for other equally important medical reasons, there may be benefits worth assuming the “risk” possibly associated with a high-protein in the short run. Bottom line: as with so many medical decisions, they must be taken in context of many other considerations.
* There appears to be more advantage for women than men.
** “Relative risk” is very different than “absolute risk”. E.g., if your relative risk of catching a cold is 20 times greater if you go to baseball games rather than not, but the absolute risk of catching a cold from going to baseball games is 0.001%, are you necessarily going to avoid going to baseball games?