Protein balance

Why, from a biological point of view, you are nothing more than the difference between protein synthesis and breakdown

All tissues of our body consist to a large extent of protein. This (and therefore also our tissues, such as the muscles, skin, hair, connective tissue, etc.) is subject to constant processes of synthesis and breakdown, so that our body must be supplied continuously with fresh building materials. The building materials necessary for tissue formation are called amino acids, which our body obtains from dietary proteins during digestion. By eating dietary proteins, we essentially supply our body with the building blocks necessary for tissue formation.

The ratio between the synthesis and breakdown of body proteins is called protein balance. Changes in protein synthesis and breakdown are triggered both by training and by nutrition. These changes mean that the protein balance is increased or reduced within a very short time, depending on training and/or nutritional measures, and ultimately you gain net protein mass (positive protein balance) or lose it (negative protein balance). For example, strength training without food intake does lead to an increase in protein synthesis (protein build-up), but due to the simultaneously increased protein breakdown it results in a negative protein balance (i.e. a net loss of body protein).

How does dietary protein affect the protein balance?

The example above shows that, even if a specific training stimulus increases protein synthesis, in the absence of dietary protein this does not result in an acutely positive protein balance and therefore does not lead to the build-up of muscle mass.

However, if you supplement strength training with the intake of high-quality dietary protein in the necessary amount, this quickly leads to a positive protein balance. The reason is that the additionally supplied dietary protein further boosts protein synthesis, which ultimately outweighs protein breakdown. As a result, the body accumulates, on balance, tiny amounts of protein. The sum of these extremely small "protein build-up surpluses" leads to measurably more muscle mass in the long term.

Certain (essential) amino acids are responsible for the increase in protein synthesis caused by dietary protein. Since different protein sources contain these amino acids in different amounts and also in different compositions, different protein sources influence muscle protein synthesis to different degrees. We will say more about this in a further article.

Central to increasing the protein balance, besides the protein source, is also the amount of dietary protein consumed. Since muscle protein synthesis cannot be increased without limit, and at the same time excessively high total protein amounts boost protein breakdown, there are biological upper limits to effective protein intake. It therefore makes no sense to consume protein amounts that are too small or excessively large in order to increase muscle protein synthesis.

Protein intake during the day

Additional protein intake during the day (e.g. when protein requirements are increased due to physical activity or in the case of "unbalanced" diets) aims to maintain muscle mass, in that the increased protein synthesis offsets the "natural" protein breakdown. The key point here is that just under 10 g of essential amino acids are sufficient to maximally increase muscle protein synthesis, whereas protein breakdown increases at protein portions > 20-25 g/portion. For this reason you should make sure to consume "high-dose" protein sources that contain as high a proportion of essential amino acids as possible. Thus, it makes little sense to consume protein supplements that maximally increase protein synthesis per portion but, due to the high total protein amount (for example 40 g per portion), also unnecessarily boost protein breakdown.

In further articles we will show you what "high-quality" proteins actually are and how they influence protein synthesis rates differently.

Sources: see linked passages