Search Articles

clear search terms

Tryptophan, serotonin and COVID – emerging paradigms in pandemic research.

June 22, 2022 | 4 Comments | Cheryl Wooster

We’re witnessing an explosion in scientific exploration of expansive aspects of COVID illness… What is the impact of the terrain – the state of the body – on the progression of the illness and on clinical outcomes? What are the most common mechanisms at play in promoting Long-Haul or Post-Covid syndrome and what interventions can help?

Today’s tip is all about tryptophan – an essential amino acid most famous for its role in serotonin synthesis and the downstream conversion of serotonin to melatonin. An important pathway, but not the primary one for tryptophan metabolism in the body. A preponderance of tryptophan is metabolized down the kynurenine pathway which plays an important role in inflammation and immunity. Research shows that elevated kynurenine metabolites correlate with serious cases of COVID disease and increases in Interleukin-6 and other powerful cytokines in the inflammation cascade. Kyunurenine upregulation promotes infection resolution, but can shunt tryptophan away from serotonin/melatonin synthesis and toward macrophage function. 

Check out this video for a helpful overview on this functional imbalance. For a quick tutorial in tryptophan/kynurenine biochemistry and its possible role in COVID, you may want to try this and this. And for a specific discussion on LHCS and the many mechanisms of how tryptophan, the kynurenine pathway and serotonin are involved, try this. This sobering study posits a direct link between kynurenine’s immune-modulatory functions and severe instances (including fatalities) of COVID-19. 

Along with the effects of the tryptophan/kynurenine pathway on immunity and inflammation, tryptophan is required for serotonin synthesis. Beyond serotonin’s role as a “happy hormone”, it is a signaling molecule that can affect other major organ systems including cardiovascular, GI, pulmonary and the CNS – and now we know it plays a role in COVID and post-COVID symptomatology. This article focuses on serotonin’s possible involvement in anosmia, ageusia, dysfunctional chemesthesis and increased severity of COVID-19 illness. And this one elucidates some of the mechanisms in the two-way communication between the immune and the nervous systems – highlighting serotonin’s role in immunity and the regulation of inflammatory responses. And of course, serotonin is needed to make melatonin, a hormone especially necessary for covid healing given its potent antioxidant properties.

Clinical long-haul COVID cases affirm a key principle of functional medicine: each patient is unique and needs customized solutions for the specific disease dynamics at play in their case. The progressive, published science on tryptophan will likely be one to watch in the year ahead.

P.S.  If you are passionate about transforming healthcare through the power of functional medicine, we encourage you to learn more about SAFM’s practitioner training programs. Enrollment for our next cohort is now open!

To receive weekly clinical tips for practitioners – like this one – right to your inbox, register here.

Follow us on Facebook and/or on Youtube to gain more rich clinical content.

4 Questions for “Tryptophan, serotonin and COVID – emerging paradigms in pandemic research.”

  1. 2
    DARYL MOSS says:
    June 30, 2022 at 12:21 pm

    Fascinating information. Do you think low tryptophan could be behind Parkinson’s patients losing their sense of taste?

    Reply
  2. 1
    Josh says:
    June 23, 2022 at 7:58 pm

    My understanding is that when there’s shunting of tryptophan down the kynurenine pathway (resulting in elevated quinolinic acid), adding tryptophan is like adding fuel to the fire. Because 5-HTP readily crosses the brain barrier and bypasses the kynurenine pathway, I’ve understood that it’s a superior option in terms of supporting serotonin and melatonin levels in these cases. I’d love to hear your thoughts on this! Thanks!

    Reply
    • 1.1
      SAFM Team says:
      June 27, 2022 at 7:07 am

      You raise an important point, yes, for some clients who are in the midst of an inflammatory challenge adding in more tryptophan could be like ‘adding fuel to the fire’, however, the quantitative and mechanistic details are still being studied. Interestingly, the research shows that people who have higher kynurenine levels at the onset of infection (meaning they already had an inflammatory dynamic going on) have much poorer outcomes than those whose number is lower (less than KYN concentrations of 4.82 nmol/L) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8750518/
      Tryptophan could be supportive post-infection when a person is trying to rebuild their immune arsenal after fighting off the virus. As discussed in this post and the associated articles, tryptophan may bring relief from the many symptoms listed in association with the COVID-19 pandemic. As Tracy said, it is a trial if this is going to work for an individual, especially for those who are already ‘doing all the right things’: healthy diet, healthy level of exercise and stress, and minimizing toxins. On the other hand, if a client is grappling with a lot of inflammation (eg., struggling with switching their diet to a less inflammatory one, taming stress, or dealing with toxicity in their body and overall environment, etc.), indeed 5-HTP and/or melatonin may be better choices.

      Reply

Ask a Question

Practitioner clarification questions are welcome! Please do not post personal case inquiries.

Hear Stories from Real Practitioners

Register Here
X