Universiteit Leiden

They might be giants

They might be giants

A vast number of high protein foods, which promise to support the muscle growth, are very common among bodybuilders. But could those dietary supplements even have the potential to influence the brain function?

This entry will not debate the spirit and purpose of food supplements for athletic reasons. This would rather be a topic for e.g. nutritionists. It’s an approach to the possible effects of those products on the human brain.

At first, we have to clarify some of the determining factors. Neurotransmitters are a kind of chemical messenger, which can be found in our body, particularly in our brain. Further there are amino acids working e.g. as precursors of neurotransmitters. One example is tryptophan, as a precursor of serotonin (5-HT). Ordinarily high protein foods contain plenty of different amino acids, much more than it could be expected in natural food. Some of these amino acids, like tryptophan can pass the blood brain barrier, while some neurotransmitters, like 5-HT can’t get into the nervous system from our stomach, even though 5-HT is  partially consisting of tryptophan.

Thus, at least a certain amount of the ingredients of those foods can be transported to our brains. So one can presume they might influence the brain function somehow. And for that reason, they can have a certain impact on ones cognition, behaviour and even emotions.  As there are over 100 known neurotransmitter and a great deal of precursor, the focus of this blog will be laid on only two substances, which are tryptophan and 5-HT.

If we take a closer look on the things going on with all the tryptophan in our body, we realise that if tryptophan is transported to our brain, there is a chance that it is metabolized to 5-HT in our brain. Even though the complete role of serotonin isn’t clear yet, we can say by now, that a balanced 5HT level has mainly positive impacts on e.g. activity and mood. What sounds like pretty good news, does not necessarily mean, that all you have to do is eat high protein foods or take a huge dose of tryptophan to be entirely happy. The trouble is that on the one hand there are diverse mechanisms in our stomach and brain and, on the other hand, varying terms and conditions, which make the whole story a little more complicated.

First of all, there is a specific and limited carrier system, which is supposed to transport proteins from the stomach to the brain. You can imagine it like a rollercoaster with a restricted number of seats. Those active carriers can transport all of the so called long neutral amino acids (LNAA), which are kind of competing. So, if your diet is rather full of proteins, then the numbers of competing LNAAs is high. As LNAAs usually don’t fight for a place in the carriers they are entering by chance. Hence, the odds are good for the most frequent LNAAs, but they are getting worse for those, which are rare e.g. tryptophan.

One other important mechanism controlling the amount of tryptophan which could enter the brain, is that 5HT can be synthesised in the stomach. If you think about the rollercoaster again, imagine tryptophan in a cue, waiting to get a ride. In that moment theme park characters, which are really interesting by the way, appear. However, they do not just want to entertain someone, they really want to get the amino acids out of the cue, give them a big hug and never let them go again. So, tryptophan and e.g. Pluto can build a connection to synthesise 5HT, which we know by now can’t enter the brain. Both mechanisms influence the serotonin level in ones brain and both depend a lot on the concentration of amino acids in your diet. There are further factors, which moderate how the body is dealing with the available tryptophan e.g. vitamins, enzymes, meta- and catabolic processes and so on. Hence, only little of the tryptophan can be used for the 5-HT synthesis in our brain or stomach.

And that means that tryptophan can be transported best, if the diet contains a lot of carbohydrate and little proteins. While reading this line as a bodybuilder, someone might think, this recommendation sounds like poisoning. But high protein foods are certainly more than just foods, whose only purpose is to help building muscles. It is very likely that at least the brain function is being influenced in some way by high protein foods. If your serotonin level is messed up, there are a lot of different aspects how it would change your mind 

-          depression might come with a lack of serotonin in your brain

-          anxiety or social phobia are correlated to a decreased serotonin concentration

-          …

That list is only a short sample of what might happen, if your serotonin level isn’t in balance.
So nowadays, it still seems like trying to enhance Mother Nature usually comes at a price.

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