Protein

How much protein do we need?

The role of protein in the diet is often viewed critically as a result of the recommendation to use as much protein as possible by the manufacturing companies, many body builders and also by some gyms.

The recommendations of the German Nutrition Society to limit daily protein intake to 0.8 g/kg body weight per day for people between the ages of 18 and 60 contradict those given by sports scientists to their members. I would therefore like to address this issue in the following.

In its recommendation, the German Nutrition Society (DGE) refers to a statement by the WHO, the World Health Organization. However, the WHO statement explicitly states that the information is a recommendation of the minimum amount of protein that people – even in countries with malnutrition – need.

WHO: Protein and Amino Acid Requirements in Human Nutrition (2007); 1 – 265; 2.5, page 24

• “Definition of requirement: The lowest level of dietary protein intake that will balance the losses of nitrogen from the body, and thus maintain the body
  protein mass, in persons at energy balance with modest levels of physical activity, plus, in children or in pregnant or lactating women, the needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health.
• It is acknowledged that this definition of the requirement in terms of nitrogen balance does not necessarily identify the optimal intake for health.”

According to the WHO, a higher intake of protein can therefore definitely offer benefits. The clear misinterpretation of the WHO by the DGE has led to a situation in Germany where too little protein is repeatedly recommended, especially for athletes and those who want to lose weight.

The problematic nature of the DGE’s recommendation becomes particularly clear when one considers the international efforts to develop the Nutri-Score which was introduced in France in 2017 on a voluntary basis and is also being discussed in Germany. In this assessment, foods are considered unfavorable if they contain a lot of sugar and fats. These have to be replaced by some kind of food. Starchy foods are one option, proteins are another sensible one. Another alternative would be alcohol. But that is certainly not what is meant! When using the Nutri-Score, there is no way around a higher protein intake!

What are proteins, which ones do we need; what are they actually for?

Proteins are chains of amino acids that are attached to each other in a sequence defined by the genetic code. (see Fig. 1) The blueprints of around 20,000 different proteins are encoded in the human genome.

You could also say: without proteins, no life:

• All metabolic processes are regulated by enzymes, special proteins
• the transport of oxygen to the cells requires hemoglobin
• the activity of muscle cells only works with a large number of different proteins
• many hormones and
• the structural proteins in skin, bones, cartilage and tendons

are just a few examples of the diverse functions of proteins.

What amino acids are there? What are the essential amino acids?

Chemically speaking, amino acids are nitrogen-containing (-NH2), short carbon chains that also contain an acid group (-COOH). Our organism uses 20 amino acids, 8 of which are so-called essential amino acids, i.e. the body cannot produce these amino acids itself, they must be supplied from outside with food. Two others are semi-essential, i.e. they can only be produced to a certain extent by the body itself.

If the blueprint of the genetic material stipulates that an essential amino acid must be incorporated during protein synthesis, protein synthesis comes to a standstill if this amino acid is not available in the cell. Similar to an assembly line, if the part to be installed, be it the wheels or the engine, is not delivered on time.

What happens then?

When all “immediately available stocks” are empty, the organism breaks down proteins into amino acids in those places where they are least important for life and are present in very large quantities: In the muscles.

As soon as the missing essential amino acid is available again, synthesis continues.

This is certainly not a problem in the short term. Around 50% of the protein in men is found in the muscles, slightly less in women. And I can’t imagine whether losing a few grams of muscle would be detrimental to our health.

However, if this goes on for longer, we will not consume enough protein in the long term, which will initially lead to poor performance and later to the dreadful images of people consisting of nothing but skin and bones, and then even absolutely essential proteins will be produced too little, with serious health consequences!

Only conceivable in developing countries? No, here too: unfortunately, not the first model has to die of anorexia!

How much protein should we reasonably consume?

Unfortunately, if you want to answer this question reasonably, you have to take a closer look at protein metabolism. And this is very complex.

Even Trump would have problems describing the events on Twitter!

Fig. 2: Protein metabolism and stock is intended to illustrate the ratios for a man weighing around 70 kg. He ingests about 70 g of protein per day and loses about 10 g in the intestines; about 10 g is also lost through the skin, hair and sweat. In addition, around 50 g of protein per day is broken down and deaminated: The nitrogen from the amino acid molecule is “dissolved out”, and excreted as urea with the kidneys. The rest of the molecule is burned like glucose or fat in the cells and used to generate energy.

If you take a closer look at the overview illustration (Fig. 2), you can see that with a normal intake – in balance – around 300 – 400 g of proteins are broken down and synthesized again every day. Since around half of the proteins are present in the muscles, it can be assumed that around 150 g of muscle protein (red line, Fig. 3) is broken down every day.

However, it is not only broken down, but also built up again (blue line). The rate of new protein synthesis is significantly higher around 2 hours after food intake, shown as a green line in Fig. 3. As a result, nothing changes with a sufficient supply of protein and unchanged strain on the muscles!

Many bodybuilders, competitive and recreational athletes hope that the more protein they consume, the more muscle protein they will build up.

It is certain that a higher protein intake – assuming a balance – does not lead to more muscle! The additional protein intake is used to generate energy. The higher energy intake causes the fatty tissue to increase!

If you want more muscle mass, you have to demand more from your muscles, e.g. do sport and exercise!

However, if you want to build muscle, you need more protein. One kg of muscle mass contains around 210 g of protein, which has to come from somewhere. To a certain extent, the body can improve the use of the nitrogen that is split off as a result of the breakdown of amino acids. But without an additional supply of amino acids, especially the essential ones, it is not possible. For this reason, sports scientists recommend that people who want to build muscle should reasonably consume at least 1.2 g of protein per kg of body weight, and up to 2 g per kg of body weight for intensive training. Bodybuilders take up to 4 g/kg. If you talk to them about the dangers of bodybuilders who dope to a very high degree, you will generally fall on deaf ears! If on the day of the competition – after having swallowed high doses of diuretic drugs – they “can no longer run for sheer strength”, then in reality the extreme viscosity of the blood is the cause of the weakness; as a doctor you just wonder why nothing more happens or is reported about it.

And how do you get more muscle?

Perhaps surprisingly at first: People who exercise break down more muscle protein during exercise – even depending on the intensity! (Fig. 4, beginning of the red line)

However, in the first two hours or so after exercise (in the “open window”), muscle protein builds up again even excessively (red line). After that, more protein is present in the muscle – at least for a certain period of time. However, if you do not train regularly, this will disappear again after about a week!

If you offer your body an additional high-quality protein in the “open window” immediately after training, which should contain as many essential amino acids as possible (especially leucine), then you can actually expect a slightly stronger muscle build-up (green line). But don’t get your hopes up! If you don’t continue to train, you will quickly lose this muscle growth again! However, it is not quite so easy to achieve a high protein intake just 1 – at most 2 hours after exercise. Of course you could hurry, run home after training and showering and fry yourself a steak or fish, for example. A shake is more convenient and certainly easy to consume in the first 2 hours after exercise – in the open window. So it’s a feasible solution.

To summarize, I would not advise a regular intake of more than 2 g protein/kg body weight, even for athletes who assume that they need a lot of muscle. If renal insufficiency is present, then an intake of more than 1 g protein/kg is clearly not advisable.

Apart from sport, are there other situations in which you should consume more protein?

Definitely yes: whenever more body protein needs to be built up, for pregnant women, nursing mothers, children and adolescents. And older people, who are obviously less able to utilize protein, should also have at least 1 – 1.2 g / kg body weight and day in their diet.

Losing weight and protein

The topic of losing weight and protein is an absolutely important chapter. If fewer calories are consumed during fasting than are consumed, the body prefers to use its fat reserves, which is absolutely desirable when losing weight. Glycogen, the sugar store, is also reduced, but this is insignificant in terms of weight. In contrast to sugar, protein – especially muscle protein – also plays an important role as an energy reservoir! With the 5 kg of muscle protein (see Fig. 2), approx. 20,000 kcal are “stored” in the muscles, which are also used to generate energy in an emergency when there is “too little food”.

However, one of the most important things when losing weight is to avoid the “yo-yo effect”! As explained above, protein, primarily muscle protein, is also used as an energy source when the calorie intake does not cover the calorie requirement. Muscle mass decreases! This can be reduced somewhat by consuming more protein, although when losing weight you must also bear in mind that 1 g of protein provides around 4 kcal!

With a higher calorie deficit, the decrease in muscle mass is quite considerable. If you end the diet phase, you will have a measurably lower basal metabolic rate due to the decrease in muscle mass. As a consequence, your weight will rise significantly above your initial weight if you eat as you did before!

For this reason, anyone who wants to lose weight should definitely be advised to do a lot of sport at the same time, to do as much as possible to maintain their muscle mass! Fortunately, this also increases your energy consumption, although this is partly provided by the increased burning of protein from the muscles. If there are not enough essential amino acids available for incorporation into muscle protein during the “open windows phase”, muscle loss can be even greater than if you had not done any sport! The joy of faster weight loss as a result of lower muscle mass will only last for a short time!

Therefore, when losing weight and exercising at the same time, you should ensure that you consume around 1.4 g of high-quality protein per kg of body weight per day, even if this leads to an additional intake of calories that you then have to save or consume elsewhere.

But how do you know how much protein you have consumed?

In the age of apps, this is not so difficult. The “fatsecret” app, for example, is practical and reliable. If you use it to determine that the intake of 1.2 g protein / kg is achieved when training to build muscle or 1.4 g when trying to lose weight with training and calorie reduction, then substitution is certainly not necessary. However, what cannot be achieved with food should be substituted; better still, the diet should be changed so that the protein intake is sufficient!

The biological value of proteins

The biological value is intended to indicate how well foreign protein can be converted into the body’s own protein and depends both on the content of essential and limiting amino acids and on the extent to which the amino acids are absorbed from the intestine into the blood.

Analyzing the composition of amino acids in a protein is methodically defined and unambiguous. It is more difficult to define the optimal composition of amino acids: On the essential amino acid that has the lowest value compared to egg? or on a requirement defined in whatever way (e.g. of small children). Higher values are obtained for advertising purposes when compared with the average for all individual values from hen’s eggs. The assessment of the value of proteins has simply not been satisfactorily resolved at present. This is why there are so many different claims, from which the manufacturers of protein supplements can choose the best ones for themselves!

It becomes even more difficult if, in addition to the content of essential amino acids, the assessment also takes into account how much of the amino acids are absorbed by the intestine.

The proteins must first be broken down into their individual components, the individual amino acids, in the intestine. Only the individual amino acids (possibly peptides consisting of 2 or 3 amino acids) can be absorbed by the intestine into the blood and thus be available to the organism to synthesize its own amino acid chains, its own proteins.

The absorption of amino acids from the intestine ends in the small intestine. Amino acid chains that reach the large intestine can no longer be incorporated into the body’s own protein. However, the bacteria in the large intestine are happy about the pieces of protein that still arrive, which they can break down into amino acids and then use for themselves.

How the food components have been pre-treated plays a decisive role in their absorption: Ground, well chewed (model cow), denatured with heat, pre-digested by bacteria or enzymes (fermented or hydrolyzed).

A great example of the differences in the value of a protein as a result of pre-treatment is soy. Entire scientific books can be filled with the relevant treatises. However, this is a very exciting topic in view of changing eating habits. (Perhaps a chapter on this topic will follow soon).

Difference between animal and plant proteinsvegetable proteins

The composition of amino acids in animal proteins is clearly more similar to that of humans and absorption is less problematic. With the usual European diet, however, it is sufficient to ensure a sufficient intake of protein overall, regardless of whether it is animal or plant-based. Vegans, however, should definitely consider which proteins they consume and combine so that they get as many essential amino acids as possible. But clearly: with a little effort, this is also quite reasonably possible.