Ever heard that wheat aka gluten is a bad protein source?
This claim has a rationale. Wheat protein is lower in essential amino acids than animal protein. Essential amino acids are those we need to get from food, as the human body can’t make them itself.
As wheat protein has a lower content of essential amino acids, it also has less of the essential amino acids leucine. Leucine is of particular importance for everyone who wants to build muscle.
Leucine has a unique function. It is not only a building block for the muscle, but also gives the signal to the body to build muscle. It’s like if you want to build a house. You need bricks and workers. Leucine is one of the bricks, but also the foreman who tells the workers to build the house.
In order to optimise muscle gains, your meals need to have enough essential amino acids (building blocks for muscle) and sufficient leucine to give the signal to the body to build muscle.
The research we had so far wasn’t supportive of wheat as a good protein source for muscle gains.
However, a recent research study has shown that after ingestion of 30 g wheat protein vs 30 g milk protein the muscle protein synthesis rates (rate at which the body builds muscle) weren't any different, even though, after milk protein more essential amino acids were present in the blood stream.
What does this mean?
1. Having more essential amino acids in blood stream doesn't necessarily translate into more muscle growth.
If the body already builds muscle at the maximal rate, giving the body more building blocks (aka amino acids) doesn’t make it build more muscle.
Let’s go back to the house building analogy. If you have a limited number of workers, bringing more building material won't make the building faster, if the workers already work at maximal speed. The limiting factor are the workers, not the building blocks.
Same applies to the amount of amino acids in the blood stream and body's ability to build muscle.
By the way, the reason why after drinking milk protein more essential amino acids were present in the blood stream is because milk protein has naturally more essential amino acids than wheat protein. It’s a no-brainer. If you ingest less, you will also detect less in the blood stream.
2. 30 g plant protein is enough to maximally stimulate muscle protein synthesis in young people (even if it's not a complete protein source).
Now leucine comes into the play. For young people 1.6 g leucine per meal seems to be sufficient to maximise muscle growth (ref).
In the research study the participants were young men and the wheat protein drink had 1.8 g leucine. It was sufficient to maximising muscle growth. Even though, milk protein drink had more leucine (2.4 g) the effect wasn’t different, because the muscle protein synthesis was already running at the maximal pace.
However, the things change when it comes to elderly people. Elderly people (over 65 years) require more leucine (at least 3.2 g) to maximise muscle protein synthesis, because age (or being more sedentary) makes muscle more resistant to growth (ref 1, 2).
For this reason, 35 g wheat protein (containing 2.5 g leucine) failed to increase muscle protein synthesis in elderly people in contrast to 35 g casein (3.2 g leucine). However, when wheat protein amount was increase to 60 g (4.4 g leucine), muscle protein synthesis substantially increased also in elderly men (ref).
Up to now we had to make recommendations based on the result of this study making it appear that consumption of 60 g wheat protein per meal is required in order to build muscle. Consuming such a high amount of protein per meal is not practical.
But now the things changed as we got more research evidence. As we see based on the results of the more recent study, young and active people require by far less protein to maximise muscle gains.
But what if I’m not young any more, but also not elderly?
Without much solid scientific literature support on this topic (it seems like most research studies examine only people in their 20s or 60-70s), my personal opinion is that there is an entire spectrum in between.
It’s not like the nature has a switch and the moment a person turns 65, the muscle need 3.2 g leucine per meal instead of 1.6 g to grow. It is more likely that the required leucine amount increases gradually with increasing age.
However, as it has been suggested that it may not be necessarily about the age but about lacking activity and being more sedentary what makes muscle resistant to growth (ref). There is the possibility that relatively young sedentary people require more leucine to maximise muscle protein synthesis than someone who is older but very active.
If you want a cookie-cutter-all-size-fits-all advice, so it is: Be as active as possible and eat enough protein.
How much protein is enough depends on your protein sources. Animal protein sources have a higher leucine content (8-11%) than plant protein sources (6-8%). (ref)
Thus, on an omnivores diet 15-20 g leucine per meal is enough to maximise muscle protein synthesis for young people and 29-40 g protein for elderly people.
For plant-based diet it’s 20-27 g protein for the young and 40-53 g protein for the elderly.
In addition to that when following a plant-based diet it is important to combine different protein sources (protein from grains and legumes). Only because consumption of a not complete protein source maximises muscle protein synthesis short-term, it doesn't mean that it will be the same long-term.
If you asked me, the bigger ‘issue’ of wheat as protein source is not its content of leucine, but of a different essential amino acid: lysine. Lysine is one of the limiting amino acids on a plant-based diet (present in low amounts). Grains - like wheat, rice, etc. - have less of it than legumes. For this reason, it is crucial to get protein not only from grains, but also from legumes (soy, beans, lentils), or, alternatively supplement with lysine if you don’t get enough from food. For details on this topic read my Vegan Protein For Maximum Muscle Gains - Complete Scientific Guide.
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