Amino acids (EAA & BCAA)

What it is

Amino acids are the building blocks of proteins. From 20 different ones, the body builds muscle, bone matrix, skin, enzymes, hormones, antibodies and transport molecules. This protein is constantly broken down and rebuilt — the body is not a finished statue but a construction site in continuous operation.

9 of the 20 amino acids are essential. They include the three branched-chain ones, leucine, isoleucine and valine, which are sold as BCAA, as well as lysine, methionine and tryptophan. The body can make the remaining 11 itself, but some of them only to a limited extent. Glycine, taurine or cysteine are therefore considered conditionally essential: under stress, in illness and in old age, the body’s own production becomes a bottleneck.

Many amino acids have tasks beyond muscle. Tryptophan is the precursor of serotonin and melatonin, tyrosine of dopamine and the stress hormones. Arginine and citrulline supply nitric oxide for wide blood vessels, glutamine is fuel for gut and immune cells, and glutathione is made from cysteine.

How it is supposed to work

After a protein-rich meal, the amino acid concentration in the blood rises, and the muscle begins to incorporate new protein. Leucine is not only a building block but also a signal: it activates the mTORC1 signaling pathway, which triggers muscle protein synthesis. For this building process, however, the muscle needs all the essential amino acids. An ignition key alone does not build a house.

In old age, anabolic resistance is added: the same portion of protein triggers a weaker building response in older muscle than in young muscle. At the same time, many older people eat less protein because their appetite decreases or meat becomes tiresome. Less signal meets a muscle that listens less well. Muscle mass and strength are among the most important foundations for independence in old age, which is why this cycle is so relevant — and it can be interrupted.

The hierarchy: food, whey, EAA, BCAA

At the top is real food: eggs, fish, meat, dairy products, legumes. Whey is a concentrated milk protein with a high leucine density and practically an EAA preparation in food form. EAA powders, that is, all nine essential amino acids in isolated form, are a sensible special solution for people with little appetite, in old age or on a purely plant-based diet.

Isolated BCAA are at the lower end. They deliver the signal, but only three of the nine building blocks. Anyone who eats enough protein has plenty of them in the blood anyway.

Plant protein works, but usually contains less leucine and lysine and is absorbed somewhat less well. The usual rule of thumb is to plan about 20 percent more total protein on a plant-based diet and to combine legumes with grains.

Distribution over the day

A common rule of thumb is around 30 grams of high-quality protein per meal with about 3 grams of leucine. A similar figure comes from studies on muscle building in older people: about 0.40 grams of protein per kilogram of body weight per meal to stimulate synthesis maximally. The typical day in old age, with a jam breakfast, soup at lunch and a single real portion in the evening, then stays below this threshold twice. The most important correction is usually breakfast: eggs, quark, skyr or a shake.

An objection from the longevity corner: permanently activated mTOR is considered to promote aging. The solution is rhythm instead of constant fire — clear protein meals with real breaks from eating in between. A large US cohort found a higher risk of death for high protein intake between 50 and 65 years of age, but a lower one above 65. This is observation, not experiment, but it shows why the recommendations shift in old age.

What the studies show

Supplements in older people (PLOS ONE 2014)

Xu and colleagues analyzed 9 placebo-controlled studies in people aged 65 and over who received protein or amino acid preparations, mostly whey, leucine in two studies and EAA in one. 267 participants received a preparation, 244 placebo. The difference in lean mass was 0.34 kilograms and not significant (P = 0.386), and leg strength did not improve significantly either. The groups studied were very different, from healthy to chronically ill.

BCAA after training (Frontiers in Physiology 2017)

Jackman and colleagues gave 10 trained young men 5.6 grams of BCAA or placebo after strength training. Muscle protein synthesis was 22 percent higher with BCAA. This shows that the signal gets through. How much of it is translated into muscle mass when the other essential amino acids are missing is not answered by the study.

Protein and mortality (Cell Metabolism 2014)

Levine and colleagues analyzed US survey data over 18 years. Those who ate a lot of protein between 50 and 65 years of age had a 75 percent higher risk of death from all causes and a fourfold higher risk of death from cancer; with plant protein, the association was weakened or disappeared. In people over 65, by contrast, high intake was associated with lower mortality.

Where the data stop

The limit lies with the isolated preparation. That protein works is undisputed; that an amino acid powder adds anything to an adequate diet is not. The meta-analysis in older people found no significant gain, and a study with leucine in older people cited in the review by Traylor and colleagues found neither more muscle mass nor more strength. The leucine threshold of about 3 grams per meal is also a rule of thumb: according to the review literature, how much leucine per meal stimulates muscle building maximally is not known and differs between young and old.

With BCAA, the discrepancy is greatest. Wolfe argued in 2017 that BCAA alone can theoretically increase protein synthesis by at most about 30 percent, because the remaining building blocks have to come from the breakdown of muscle protein. The observation from the cohort on protein and mortality is, moreover, only an association and may be distorted by other lifestyle factors.

Status, approval and legal

In Germany, amino acids and protein powders are foods or food supplements, not medicines. There are no legal maximum amounts for protein from normal foods. The reference values of the German Nutrition Society are 0.8 grams per kilogram for adults under 65 and 1.0 gram from 65 years. Amino acids are not on the doping list. As with all sports products: food supplements can be contaminated; competitive athletes pay attention to tested batches.

Safety

For healthy people, a higher protein intake is considered safe. A meta-analysis of 28 studies with 1,358 participants without kidney disease found no change in kidney function from a high-protein diet. It is different with existing kidney impairment: the PROT-AGE group explicitly excludes older people with severe kidney disease, that is, a filtration rate below 30, who are not on dialysis, from the higher recommendation. Anyone with kidney disease should clarify the amount of protein with a doctor. Isolated amino acids in large amounts are less well studied than protein from food.

Sources

• German Nutrition Society (DGE), reference values for protein
• Bauer et al., J Am Med Dir Assoc 2013 (PROT-AGE)
• Traylor, Gorissen, Phillips, Adv Nutr 2018
• Morton et al., Br J Sports Med 2018
• Xu et al., PLOS ONE 2014
• Jackman et al., Front Physiol 2017
• Wolfe, J Int Soc Sports Nutr 2017
• Levine et al., Cell Metab 2014
• Devries et al., J Nutr 2018