Those of us trying to keep up with the latest scientific findings on nutrition have probably been confused lately: first, at the end of July, a major review study called into question the primacy of protein for healthy aging, while last week another study concluded that the high-fat, extremely low-carbohydrate ketogenic diet is superior to the Mediterranean diet and the low-fat diet when it comes to protecting the liver.
But what does all this mean? And how can we incorporate these findings into our lives? Before we start cutting back on protein and eating bacon in large quantities, it is worth looking at the findings of these studies with a critical eye.
The full protein
We live in an age in which protein is being glorified, and with the help of marketing, the message that “the more, the better” has reached everyone. This has, of course, created a huge market: protein bars, rich yogurts and cereals, special drinks and other foods are being purchased in large quantities with the aim of increasing daily protein intake.
According to the findings of a major study that evaluated more than 350 scientific papers, however, chronically excessive protein intake may not be as beneficial for longevity as it is often portrayed to be. In some cases, in fact, lower protein intake appears to be associated with metabolic changes linked to healthier aging.
At first glance, this finding appears to contradict the prevailing view that older people may need more protein than is recommended for a younger adult. This is because, as we age, we gradually lose muscle mass and strength. This process, known as sarcopenia, can reduce our mobility and increase the risk of falls. Thus, dietary recommendations worldwide suggest approximately 1.0-1.2 grams of protein per kilogram of body weight per day for healthy older adults, and even higher amounts for those who are particularly active or who are ill and malnourished.
So where does the truth lie? Probably in not oversimplifying things and in not assuming that the answers to difficult problems involving living organisms can be given through universally applicable numbers of grams of dietary components.
The complexity of being alive
The recent review study was based on decades of findings showing that restricting total calorie intake increases survival in organisms studied in the laboratory. The researchers wanted to examine the issue in greater detail and investigate how restricting protein intake affects survival. Thus, through their review of hundreds of studies on the subject, they found that protein, which indeed helps maintain muscle, can, under certain conditions, activate biological pathways that are not necessarily favorable to longevity.
More specifically, they found that, in experimental models, lower protein intake is associated with improvements in metabolism, reduced inflammation and less cellular damage. Clearly, this study, which was published in the scientific journal Cell Press Blue, overturns the oversimplified idea that more protein means better health. But under no circumstances does it constitute a recommendation for older people to follow a low-protein diet!
For a person who is already struggling to maintain muscle mass, inadequate protein intake may be far more dangerous than any theoretical benefit that could result from restricting it. Conversely, for a relatively young adult who leads a sedentary lifestyle and already consumes large amounts of protein, adding even more protein may have harmful long-term consequences for their health and longevity.
It is worth noting that the scientists identified precisely the areas in which long-term excessive protein intake has a negative effect, including cellular senescence, mitochondrial function (cellular organelles responsible for energy production), and epigenetic changes (changes to DNA that do not alter its sequence but affect gene expression).
These findings force us to remember that “the devil is in the details.” The need for protein is influenced by age, physical activity, overall diet, health status and muscle mass. And this is something that today’s obsession with a universal daily protein-intake target often overlooks. Just as it overlooks the very important factor of where the protein comes from.
Previous studies in humans have shown that the relationship between protein and healthy aging may depend on the type of protein and our overall diet. A dietary pattern based on fish, legumes, dairy products, eggs, nuts, vegetables and whole grains is consistently shown to be preferable for healthy aging. And it is very different from a diet that seeks to maximize protein through processed products.
In other words, the amount of protein may be one of the factors we need to take into account if we are aiming for healthy aging, but at the same time we must ask ourselves which foods it comes from, what it replaces in our diet, and what our needs are at each stage of our lives.
And, of course, we must remember that a food does not automatically become healthy simply because it contains more protein.
What does a ‘better’ diet mean?
As broad as the study on the relationship between protein intake and healthy aging was, the study comparing the ketogenic, Mediterranean and low-fat diets was just as small. Only 42 of the participants completed the study, which involved people with obesity, prediabetes and elevated liver fat — that is, a group considered to face increased metabolic risk.
According to the relevant article, which was published in the scientific journal Cell Metabolism, the participants were randomly assigned to one of the three diets, and the scientists made sure that, by regulating calorie intake, everyone lost approximately 10% of their initial body weight over the five months that the study lasted.
And, as was rather expected, in all three cases the weight loss led to an improvement in the participants’ metabolic profiles. There was, however, also an unexpected finding: the ketogenic diet led to a reduction of approximately 67% in intrahepatic fat, compared with approximately 45% in the Mediterranean and low-fat diet groups.
This finding, which received widespread publicity with headlines along the lines of “the ketogenic diet beats the Mediterranean diet,” sparked a major discussion among leading nutritionists on social media. They felt the need to clarify that the study was not a “beauty contest among diets” and to emphasize that it concerned a very specific group within the population.
They also stressed that the benefits of the ketogenic diet for this particular group need to be confirmed in broader studies, as they could perhaps be used for personalized interventions in specific patients.
As for the rest of us, experts continue to recommend the Mediterranean diet, which is based on a wide variety of foods and can be incorporated relatively easily into everyday life.
Because the best diet is not the one that produces impressive results within the framework of a controlled clinical trial, but the one that is effective, safe and, above all, one that a person can consistently follow for years.
