Protein and Aminoacids

Building blocks and sources of protein.

Everyone needs protein. Period. It is not just the big muscular gym guy, also you sitting in the chair diligently doing your job or you, running a half-marathon or you, playing football. Why? Because proteins are the brickstones of our body, they are the catalysators (= enzymes) of our metabolism and are also fuel. After water (70%), proteins (18%) are the second main component of human cells. That’s why it may be worth considering adding more protein to your daily food, especially if you are getting serious about living a more active and healthy lifestyle.

Let’s take a closer look at this gorgeous, muscle building molecules before you head up to the kitchen to roast your steak or vegan pulled pork ;).


If you have read my macronutrients article, you now know that proteins are made of specific aminoacids (AAs), called the proteinogenic aminoacids. We get AAs for the synthesis of proteins either from food or by synthetising them from other molecules. Therefore we can divide them in:

  • non-essential AAs: we are able to synthetize them by our own
  • essential AAs (EAAs): we are NOT able to synthetize them by our own and have to take them up with food
  • conditionally essential AAS: we can synthetize them but synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress.
Non-essential AAsEAAsConditionally essential AAs
Aspartic acidIsoleucineCysteine
Glutamic acidLysineGlycine
Proteinogenic aminoacids

Where do I get my aminoacids from?

There are a lot of protein sources out there, but -as you may guess- it is not just about the quantity, it is also about the quality of the protein. The quality is determined by many factors such as  the AAs profile, the leucine content and other components influencing the AAs uptake and protein synthesis (either limiting or pushing it). Here is a rough quality guideline to choose where to get your aminos from (vegan, vegetarian):

  • High quality: whole diary, meats, fish, whole eggs, milk protein, casein protein
  • Moderate quality: pea protein, hemp protein, rice protein, whey protein, hydrolyzed protein
  • Low quality: soy protein, other vegetarian protein sources

There is no need to sip protein shakes if you manage to cover your protein intake requirements with whole foods since most of them are high quality protein sources. Nevertheless, you can still use supplements as a tool as they are often well digestible and easy to carry with.

Sometimes foods like broccoli, peanut butter, beans or even oats are referred as protein sources but their protein content is not significant in regards to their calories or their portion size. Here is a graph made by Stefan showing the grams you need to reach 25 grams protein and the calorie content of the size. Let’s take a look.

Protein sources ranked by kCal spent to consume 25g of protein from the least calories (lean beef) to the most (potatoes)

If you would like to have 25 gramms of protein it’s enough to eat:

  • a scoop (around 30 gramms) of whey
  • a scoop of vegan protein blend (usually a rice – hemp – pea protein mix)
  • a 120 gramm chicken breast

all three having around 130 kCal. You get a real good amount of protein without having to go skyhigh with calories or eat a huge unrealistic portion size. Now let’s compare them with broccoli, beans and peanut butter, three sources that are commonly told to be high in protein. For 25 gramms of protein you need:

  • 660 gramms of broccoli (224 kCal)
  • 300 gramms of beans (315 kCal)
  • 83 gramms of peanut butter (437 kCal)

Even by eating the low caloric broccoli, you need to eat almost twice as much calories to reach the same amount of protein, which would be fine if you wouldn’t need to eat 660 grams (!!!) of broccoli. Have you ever tried it? I wouln’t advice.

What about beans? If you tolerate them well (300 grams is still a generous bean portion!) and you are not restricting carbs (and calories) they are maybe on the more reasonable side from the caloric load and portion side. Still, they are rather a carb source with a nice amount of protein than a protein source.

My favorite one is peanut butter. A lot of companies sell it for a high price as a “protein spread”. To get you 25 grams of protein you need 437 (!!!) kCals from 83 grams peanut butter which are moderately satiating. Peanut butter is great, but it is rather a fat source with some protein than otherwise.

Last word about oats because they came up during a lecture. To reach a 25 gram protein portion you need to eat 125 gramms of oats with a caloric intake of almost 700 kCals. Again, oats are great, full of fibre, satiating and tasty, but they are a carb source with a tiny amount of protein.

leucine threshold

Leucine is one of the EAAs and it’s not only a proteinogenic AA but also capable of modulating muscle protein synthesis (MPS). In research, it’s still under discussion if you need to reach a minimum amount of leucine per meal (“leucine threshold”) to allow MPS to start or if it happens in a dose-dependent manner.

On the practical side I wouldn’t bother much and -to be on the safe side- assure that you spread your protein intake rather eavenly through the day. Ideally, you would have something like 0,3g/kg bodyweight protein per meal if you eat animal-based protein sources and 0,5g/kg bodyweight if you eat only plant-based protein sources as they are lower in leucine content.

aminoacid metabolism

When our body needs AAs it either gets them from breaking down protein from food or from the body (mainly muscle and connective tissue, but potentialy every protein in the body). Protein digestion mainly occurs in the stomach, then the AAs (or smaller protein pieces) are absorbed in the intestine and transported to the liver for metabolism via the blood flow.

AAs are used as building blocks of every protein in our body from muscle mass to connective tissue to antibodies (immune system!) to enzymes driving our metabolism and nearly every function in the body you can think of. This happens when the diet is adequate in providing energy and other nutrients. For strength trainees the building of muscle tissue is of course the most interesting one. Adequate protein intake and challenging resistance training are key to start muscle protein synthesis.

Skeletal muscle protein synthesis model by Witard et al. 2016

AAs breakdown occurs in periods of prolonged fasting (e.g. during night rest or a fast) and when intake of other nutrients is inadequate. AAs are then converted to glucose (gluconeogenesis), energy, other compounds and can even be stored as fat.

Synthesis and breakdown normally occurs in different part of the body during the whole day. The net balance determines if we are rather building up (muscle) protein or not. On top of that, hormones play a huge role too whether you build muscle tissue or not.

to sum it up

If you are consuming approximately 1,5-2 gramms/bodyweight protein from different sources with all the EAAs, if you are not in a state of fasting, if you are training consistently hard enough and your stress level are somehow in check, protein balance should be rather on the anabolic-muscle building side. Which is definitely the good side ;-).

If you want to know more about protein, be sure to check this article by Stefan, where he sheds light on some common protein myths. And if you need some inspiration on how to prepare tasty protein-containing dishes scroll through our recipe section. For further questions hit the comment section below, we are more than happy to help you!

P.S.: Do you need help with your diet or your training? Feel free to contact me. If you are already determined to get working, fill out this application form.

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