Gut series: serotonin
The gut is a huge topic and one post just won’t cover it. We are going to break it down, learn the basics, but also get into some exciting research.
I will have a separate post for gut basics, but today we are going to discuss a topic I know so many of you are interested in. Serotonin and the gut.
What we know:
About 90% of the serotonin in the body is produced in the cells lining the GI tract
It plays a very important role in GI function (peristalsis, secretion of digestive enzymes, sensitivity to discomfort)
Helps transmit information about the gut to the central nervous system (through ENS)
Gut microbiota can possible influence serotonin synthesis and release
Imbalanced gut serotonin levels can lead to GI disorders
The basics
If you’re like me, first you want to know how the gut makes serotonin. We start with the uptake of tryptophan (we love her) from the bloodstream and into enterochromaffin cells (cells in the lining of the GI tract). Inside these cells tryptophan is converted into 5-hydroxytryptophan (5-HTP) — if you’re wondering if this is the same as the supplement a lot of people take, it is. Then, an enzyme converts 5-HTP into 5-HT aka serotonin. Once serotonin is made its stored in the cells and waits to be released. Things that can trigger the release are mechanical stimulation, chemical stimulation, neural signaling, presence of food in the stomach, and tryptophan intake. When serotonin is released, it can either work in the GI tract or head to nerves close by and influence the enteric nervous system. We have certain mechanisms in place to regulate our levels but we won’t get too deep into that in this post. One thing to note is that tryptophan metabolism has a lot of different pathways, and if some of them are over active it is not so great. In the takeaways at the end I will discuss how we can help those pathways stay in check.
The serotonin that we make in the gut does not travel directly to our brain because it cannot pass the blood brain barrier, however!! it does play a role in gut-brain communication which can influence our mood and well-being.
things you are probably wondering
How does this impact my gut issues? Well, the most simple way to say it is: too much serotonin may increase gut motility leading to diarrhea, and too little serotonin can decrease gut motility leading to constipation.
What about the digestive enzyme part? Inadequate serotonin signaling can potentially mess up the release of hormones that are involved in the secretion of digestive enzymes.
Do medications that impact serotonin play a part in this? Elevated levels of serotonin mean increased gut motility soooo you can absolutely have GI symptoms when taking these medications. I was curious to understand more about this. I did a deep dive and learned a few more things. SSRI’s can have an “antibiotic” effect on the gut, the gut microbiome may have impact the functionality of SSRI’s, and the vagal pathway connecting the gut to the brain is something that needs to be studied way more when it comes to psychiatric disorders.
If you are curious too, click here. And here.
Takeaways
For me, learning all of this made me want to do a few things.
Increase foods high in tryptophan! We need tryptophan for serotonin. Whole milk (iykyk), poultry, pumpkin seeds, beef, salmon, eggs.
I mentioned something about how tryptophan metabolism can go a few different ways. One pathway specifically is the kynurenine pathway (something worth looking up). We want to make kynurenine, but just enough, not too much (can mess with our immune response). In order to do that it’s been shown that fermented foods and methyl rich foods (beets, dark greens, turmeric, shiitake mushrooms) help and also exercise!
Vagal nerve stimulation, probably the most important. Singing, humming, gargling, reflexology, deep breathing, and laughing.
Start with googling some jokes to make you laugh :)