Low Serotonin and Gastrointestinal Disorders

Written by: Kevin Cann

            Serotonin is one of our neurotransmitters that are responsible for our mood.  If our serotonin levels fall off we may experience anxiety and depression.  More information about serotonin can be found in a previous article I wrote here, http://robbwolf.com/2012/10/05/serotonin-deficiency-food-cravings/.  What many people do not understand is that serotonin also plays a role in gastrointestinal disorders.  In fact, the majority of our serotonin is produced in the gut, roughly 95%.

Serotonin is produced in the enterochromaffin cells (EC) in the intestinal mucosa.  Serotonin is produced, and then it bonds with its receptors.  These receptors are known as the 5-hydroxytryptomine receptors, or as they will be referred to here on out as 5-HT receptors.  Once the serotonin is released, it activates our system to increase intestinal motility.  Research has shown that there is an increase in plasma 5-HT during diarrheal diseases, and a decrease in them when constipation is present (Cammilleri, 2009).

These receptor sites are actually targets for medications when treating diarrhea and nausea. 5-HT (3) receptor antagonists are used during chemotherapy treatment to help alleviate symptoms and 5-HT (4) agonists are used to help treat constipation (Costedio, 2007).  Therefore, if we have too little, or too much serotonin floating around we can experience all kinds of common gut issues.

Selective Serotonin Reuptake Inhibitors (SSRIs) are the most commonly prescribed antidepressants.  They too work upon the same serotonin pathways to help aid in depression.  Common side effects of SSRIs are nausea, diarrhea, and nervousness.  All issues associated with improper levels of plasma 5-HT receptors.

The new path of the medical community seems to be leading towards drugs that affect the serotogenic pathways to treat IBS.  One such drug is a 5-HT antagonist and it is called Alosetron.  In one study, Alosetron showed to be beneficial in treating global IBS symptoms in women with IBS that were experiencing diarrhea symptoms.  This was after conventional therapy had failed (Mayer, 2003).  Studies have even shown it beneficial in reducing symptoms of anxiety.

On the other end of the spectrum we have IBS with constipation.  Treatment for this is leading to medications that act as 5-HT agonists.  One of those drugs is Renzapride.  Cammilleri and colleagues showed that Renzapride was associated with improvement of bowel function in women (Cammilleri, 2004).

The Understanding of IBS and its roots are still up in there.  Chances are it is not just caused from one factor.  What we do know is that poor gut health can lead to poor mood and vice versa.  Our serotonin pathways may be a large player in this part.  Due to this understanding, we want to take action in making sure we have adequate serotonin.  We do this by getting proper sleep, having proper vitamin D levels, getting sufficient sunlight, not drinking too much alcohol or coffee, and eating high quality protein.  We need to make sure we also have good digestive health.  Without proper digestion, the tryptophan and the nutrients required to convert it into serotonin may not be present.

If you are suffering from IBS and dietary changes and conventional therapies are not working, you may want to seek out a qualified health practitioner and have your serotonin levels checked.  Simple 5-HTP, or L-tryptophan supplementation may be all you need to help alleviate specific symptoms.  The other neurotransmitters may also play a role in IBS as well, and I will discuss those in future articles.  The vagus nerve that allows for communication between our gut and our brain is a two way street.  Sometimes healing the mind will heal the gut and vice versa.  Eat nutrient dense foods and manage your stress, and you will be surprised at how far just those two little things can take you.









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  1. The Pooch says

    Does serotonin (or other neurotransmitters) produced in the gut affect the brain? Can serotonin from the gut cross the blood-brain barrier? Thanks! Very interesting article.

  2. says

    Another method of treating this is by considering whether or not fermentable carbohydrates are the issue at hand- particularly the class referred to as FODMAPs. Some studies have shown that restriction of these carbohydrates reduces symptoms of depression- possibly by increasing serum tryptophan levels, which are required for the production of serotonin.

    Hopefully more awareness of this will decrease the often unnecessary practice of prescribing side-effect-heavy anti-depressants to patients with IBS with the usually mistaken belief that depression causes IBS instead of the other way around.

  3. says

    It’s interesting that serotonin also plays a role in platelet aggregation and other aspects of inflammation. It’s a multi-purpose molecule, not just a neurotransmitter, and this may complicate treatment of the depression-as-inflammation model.
    Serotonin levels can be adjusted with niacinamide without adding extra tryptophan into the system, as conversion to NADH is a tryptophan degredation pathway.

  4. Kim says

    A word of caution on 5-HTP: while I had good results in terms of sleep quality and reducing cravings, I also experienced increased GI distress. Fortunately, I eventually noticed the warning on the bottle that people with GI disorders should not use 5-HTP. So, in this context, 5-HTP isn’t a great recommendation.

    I’m looking forward to your future posts on GI and neurotransmitters. Would definitely like to see a post on increasing serotonin without supplements.

  5. says

    I guess fluctuating levels of serotonin play a part in some cases of autism. I see the mood swings of my nephew and the gut problems he’s had over the years.

  6. joanna says

    this is very interesting. i have ulcerative colitis and i’ve been looking into wellbutrin for my symptoms. i’ve read that it’s a tnf inhibitor but not sure what it does for serotonin levels. anyone know?

    • kevin cann says

      Hey Joanna,

      Wellbutrin is a MAOI inhibitor. Not too too familiar with it, but there are two types MAO-A and MAO-B. MAO-A stops the breakdown of serotonin, norepinephrine, and dopamine. MAO-B stops the breakdown of dopamine.

  7. says

    It doesn’t look like Wellbutrin is a proper MAOI (though plenty of chemicals like this have a weak competitive action). It’s more like an amphetamine. Wiki says “Its primary pharmacological action is thought to be norepinephrine-dopamine reuptake inhibition. It binds selectively to the dopamine transporter, but its behavioural effects have often been attributed to its inhibition of norepinephrine reuptake.”
    There are no gut effects listed. http://en.wikipedia.org/wiki/Bupropion

  8. says

    Some years ago due to some drastic changes in my life I started to inquire into myself and found out that I was not as happy a person as I thought myself to be. Months of soul-searching, but little did help me to find my happiness. Then someone introduced meditation to me. I meditated on a regular basis for over a year but still despite it was confused, disappointed and angry inside. Constant moodiness was a normal state of being at the time and nothing or no one seemed to be able to alleviate it.

    Then a friend invited me to a ceremony with a shaman from Latin America. He told me that a certain psychedelic mushroom will be used. I was curious and agreed to participate. For some two weeks after the ceremony I was on top of the world. Then many more ceremonies followed in the course of two years and I can say, believe it or not, these helped me more than anything else to find myself and be more happy. These days I wake up with a smile…

    There’s this curious article on telegragh.co.uk that states that magic mushrooms may even be a cure for depression. If interested read it here: http://www.telegraph.co.uk/science/science-news/9976077/Magic-Mushrooms-treatment-for-depression-being-delayed-by-drug-laws.html

    Also, I agree with you that vitamin D, sunlight, sufficient sleep, a healthy diet and I’d add plenty of exercise I am sure are able to boost serotonin levels. I vote for regular exercise, plenty of sleep and a good diet as these too no doubt helped me to cure myself…

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