PROTEINS, LONGEVITY AND MUSCULAR MASS

PROTEIN, MUSCLE MASS AND LONGEVITY

I have realized that many people are not truly aware of how crucial protein is for long-term health. The purpose of this insight is to raise awareness of how important it is to consume an adequate amount of protein. Protein intake has been shown to be associated with higher bone density in adults over the age of 65 (1), and muscle mass is one of the most important indicators of longevity (2).

If we remove water and fat reserves, the human body is essentially made of protein.

Proteins have many functions in the body:
immune, antibodies
contractile, muscles
enzymatic
hormonal
structural, collagen
storage, ferritin which stores iron
transport, hemoglobin which carries oxygen, or lipoproteins which transport cholesterol

The human body is literally built from proteins. Only about 1% of our body weight is made up of carbohydrates, while fat mass depends on physical condition. A male athlete typically has 6–14% body fat, a female athlete 14–20%. Women naturally carry more body fat because they need additional energy reserves in case of pregnancy. Throughout human evolution, food availability was inconsistent and periods of famine were common, so the female body adapted to store more energy to support reproduction.

Proteins are made up of amino acids. They are like necklaces of pearls, where each pearl is an individual amino acid. The human body contains more than 100,000 different proteins, all built from just 20 amino acids.

These twenty amino acids are divided into:
Essential, which cannot be produced by the body and must be obtained from food
Non-essential, which the body can synthesize

In recent years, a further category has been introduced: conditionally essential amino acids (3). These are amino acids that are normally non-essential but, under certain conditions such as stress, illness or injury, are not produced in sufficient amounts and therefore need to be supplied through the diet:
Arginine
Cysteine
Glutamine
Glycine
Proline
Serine
Tyrosine

For example, people with diabetes, metabolic syndrome, fatty liver or obesity have lower circulating levels of glycine in the blood. Glycine supplementation has shown positive effects, improving insulin sensitivity and exerting antioxidant and anti-inflammatory effects. The foods richest in glycine are collagen, gelatin, skin, tendons and joints of animals (4,5).

Proteins that contain all essential amino acids in the correct proportions for humans are animal proteins, which is why they are often referred to as “complete” or “high-quality” proteins. Plant proteins also contain essential amino acids, but:
in most cases they do not contain all of them
in all cases they do not contain them in the proportions required by the human body

Is it possible to obtain enough essential amino acids from plant proteins alone? Yes, but it requires consuming significantly more calories and a considerable amount of antinutrients such as phytates and lectins, which are not present in animal proteins.

So why is it often said that animal protein is harmful and that red meat causes cancer? Honestly, I struggle to find a rational answer. The only explanations I can come up with are:
lack of knowledge
a system that benefits from an unhealthy population

I have written a detailed this insight on the topic “does red meat cause cancer?”. I strongly recommend reading it, as it helps clarify how many nutritional claims are based on personal beliefs rather than solid scientific evidence.

SARCOPENIA, PROTEIN AND EXERCISE

Sarcopenia is a progressive and often unnoticed process characterized by a 3–8% loss of lean muscle mass per decade after the age of 30. It is estimated to affect 30% of individuals over 60 and more than 50% of those over 80 (6).

Although muscle protein synthesis is regulated by many factors, the fundamental requirement for building muscle protein is the availability of dietary amino acids.

Most studies suggest that an adequate protein dose stimulates muscle protein synthesis similarly in young and older adults. However, when protein and carbohydrates are consumed together, older adults show a reduced muscle protein synthesis response compared to younger individuals. Fortunately, even moderate physical activity can improve this response.

Recent studies show that aging is associated with an inability of skeletal muscle to respond to low doses of essential amino acids, around 7.5 g, while higher doses, 10–15 g, stimulate muscle protein synthesis similarly to what is observed in younger individuals. Plant proteins contain fewer essential amino acids than animal proteins.

To maximally stimulate muscle protein synthesis, about 25–30 g of high-quality protein is needed per meal, meaning protein that provides at least 10 g of essential amino acids. Reaching this amount at each meal is an effective strategy to preserve muscle mass after the age of 65.

Age-related muscle loss is mainly due to reduced muscle protein synthesis rather than increased muscle protein breakdown. While synthesis declines slightly with age, this reduction is relatively modest. Physical inactivity is one of the main contributors to sarcopenia. The good news is that muscle, even in older individuals, responds very well to exercise, especially resistance training (7).

Protein intake positively affects both muscle mass and bone density (1), and these recommendations are not limited to people over 65. Adequate protein intake is essential at every age.

Thanks to paleopathology studies (8), we know that Paleolithic human diets were largely based on animal protein, as indicated by high nitrogen levels in their bones. With the advent of the Neolithic period and agriculture, human health declined: shorter stature, smaller cranial volume and reduced bone density (9). These changes were likely due to lower protein intake and higher consumption of antinutrients such as phytates, which impair mineral absorption.

This pattern is also supported by the work of Dr. Weston A. Price (10). When populations transition from ancestral diets to Western diets, dental caries increase and dental arches deform. Bones and teeth are essentially mineralized collagen, which is a protein.

ADEQUATE PROTEIN INTAKE

So what is the correct protein intake? There is no definitive answer, but we know it depends on age and activity level.

Leading experts suggest consuming 1.5–2.0 grams of protein per kilogram of body weight. In the case of overweight individuals, ideal body weight should be considered. Higher levels of physical activity require higher protein intake.

Is there an upper limit? Based on urea synthesis capacity, researchers estimate that a healthy adult can tolerate up to 3.5 g of protein per kilogram of body weight without adverse effects (11). We know this is safe because traditional Greenland Inuit diets were almost entirely based on animal protein, with daily intakes of about 280 g of protein, 135 g of fat and 54 g of carbohydrates, without evidence of kidney, liver or cardiovascular disease.

For someone with an ideal body weight of 60 kg, this translates to 90–120 g of protein per day. Is eating 150 g of meat per day enough? Absolutely not.

Here is how much protein is found in 100 g of various foods:
Parmigiano Reggiano, 32.4 g protein, 397 kcal, 12 kcal per g of protein
Beef sirloin, 23 g protein, 132 kcal, 6 kcal per g of protein
Amberjack, 23 g protein, 146 kcal, 6 kcal per g of protein
Chicken, 21.2 g protein, 114 kcal, 5 kcal per g of protein
Anchovies, 20.3 g protein, 131 kcal, 6 kcal per g of protein
Salmon, 20 g protein, 142 kcal, 7 kcal per g of protein
Sea bream, 18.9 g protein, 105 kcal, 5 kcal per g of protein
Mackerel, 18.6 g protein, 205 kcal, 11 kcal per g of protein
Sea bass, 18.4 g protein, 97 kcal, 5 kcal per g of protein
Squid, 16 g protein, 92 kcal, 6 kcal per g of protein
Shrimp, 13.6 g protein, 72 kcal, 5 kcal per g of protein
Eggs, 12.5 g protein, 143 kcal, 11 kcal per g of protein
Mussels, 11.7 g protein, 351 kcal, 30 kcal per g of protein
Cow’s milk ricotta, 8.8 g protein, 146 kcal, 17 kcal per g of protein
Cooked lentils, 6.9 g protein, 92 kcal, 13 kcal per g of protein
Full-fat Greek yogurt, 6.4 g protein, 115 kcal, 18 kcal per g of protein
Cooked peas, 4.5 g protein, 68 kcal, 15 kcal per g of protein
Cooked cannellini beans, 7.3 g protein, 114 kcal, 16 kcal per g of protein
Tofu, 8 g protein, 76 kcal, 9.5 kcal per g of protein

For each food, I have also listed the caloric content of 1 gram of protein, I think it may be useful for those who are trying to lose weight.

If you want to look up this information on other foods do so here, on the Crea website.

Beware of dairy products: they contain caseins that can be inflammatory. Goat and sheep are less problematic because they contain betacasein A2.

Collagen deserves special mention: 100 g of collagen contains 93 g protein = 369 kcal = 4.1 kcal/g protein. However, collagen is not a high biological value protein as it does not contain all the essential amino acids. The 52% of amino acids it provides are glycine, proline, and hydroxyproline. As we have seen glycine and proline are conditionally essential, and circulating glycine is low in people with metabolic syndrome, diabetes, fatty liver, and obesity.

My personal position is that 25% of protein intake should come from collagen, as the body cannot produce all the glycine it needs (even when healthy) (12) and if it does not have glycine it cannot produce new collagen. For more on this topic click here.

How to take 30 g of protein:
130 g of beef
141 g of chicken meat
158 g sea bream
240 g eggs (or 4 medium eggs)
proteins can be mixed, no problem.

Last remark: foods also contain micronutrients; foods of animal origin contain many more. In this chart (13) we can see how many calories of each food are needed to take 1/3 of the daily requirement of vitamin A, folic acid, vitamin B12, calcium, iron and zinc. As we can clearly see, there is no food richer in micronutrients than liver!