Have you ever felt tired for no clear reason? Or noticed mood swings, brain fog, bloating, achy joints, or slow recovery after exercise? Many people feel these symptoms and never get real answers, even when their doctor says their bloodwork looks normal.
Surprise, surprise, surprise. These common symptoms can be early signs of hidden inflammation inside your gut and immune system. For people who like to be proactive and focus on prevention, one of the best markers to look at is Kynurenine, also known as KYN.
Kynurenine shows whether your immune system is calm or stressed. It provides early warning signs long before more serious problems appear. This is something everyone would want to know. That is why I wrote this article: to help you understand what Kynurenine (KYN) is, why it matters, and how the Gut Health Test I endorse uses Kynurenine, among other signals, to reveal what is happening inside your body.
As you read this article, I encourage you to take your time. Read each section, think about what it means, and feel free to go back and re-read anything that feels new or unfamiliar. This isn’t a race. Each part of this article is designed to build on the one before it, giving you a simple “stepping-stone” path toward full understanding.
And if you ever want a deeper, more complete understanding of gut health, inflammation, and the microbiome, consider taking our online course, Gut Health & Microbiome Specialist. It’s designed for everyday people and health professionals who want evidence-based knowledge they can use to help themselves and others.
Before We Go Further: What Is Tryptophan, Serotonin, and Indole-3-Propionic Acid (IPA)?
To understand Kynurenine (KYN), it helps to know about three important compounds your body relies on:
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- Tryptophan
- Serotonin
- Indole-3-Propionic Acid (IPA)
I also wrote a full article about Indole-3-Propionic Acid (IPA). You can read it here:
👉 https://www.dietfreelife.com/your-gut-health-could-be-the-reason-you-feel-tired-moody-or-inflamed/
What Is Tryptophan?
Tryptophan is an essential amino acid you must get from food. Foods rich in tryptophan include turkey, chicken, salmon, eggs, dairy, beans, lentils, nuts, and seeds.
Your body uses tryptophan to make:
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- Serotonin
- Kynurenine (KYN)
- Indole-3-Propionic Acid (IPA)
Where your tryptophan goes tells a story about your mood, gut health, and immune function.
What Is Serotonin?
Serotonin is a chemical messenger that affects:
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- mood
- sleep
- appetite
- digestion
Around 90 percent of your serotonin is made in your gut, not your brain.
What Is 5-Hydroxytryptophan (5-HTP)?
5-Hydroxytryptophan (5-HTP) is the middle step your body uses to turn tryptophan into serotonin.
Simple pathway:
Tryptophan → 5-Hydroxytryptophan (5-HTP) → Serotonin → Melatonin
Your body makes 5-Hydroxytryptophan (5-HTP) in both the brain and the gut.
When inflammation rises, less tryptophan is sent toward serotonin. Instead, more of it is pushed into the Kynurenine pathway (explained later in this article). As Kynurenine levels rise, inflammation often increases, which can lead to:
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- low mood
- poor sleep
- low energy or fatigue
This shift is one of the reasons people with chronic inflammation often don’t feel like themselves.
What Is Indole-3-Propionic Acid (IPA)?
Indole-3-Propionic Acid (IPA) is a powerful antioxidant made only by your gut bacteria. Your human cells cannot make IPA without the help of your microbiome.
High IPA means:
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- stronger gut barrier
- lower inflammation
- better microbial diversity
- better protection of brain and gut tissue
Low IPA often points to:
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- weak microbial diversity
- low fiber intake
- inflammation inside the gut
What Is Kynurenine (KYN)?
Kynurenine (KYN) is made by your body, not your gut bacteria. It is produced in:
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- your liver
- your immune cells
- your gut lining
- your brain (in small amounts)
Your body increases Kynurenine production when it detects:
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- inflammation
- infection
- chronic stress
- autoimmune activity
- poor omega-3 intake
- high omega-6 intake
- a weakened gut barrier
High Kynurenine = immune system stress
Low Kynurenine = low tryptophan availability or an exhausted immune system
The Three Pathways of Tryptophan
Tryptophan can move through three main pathways:
- Serotonin Pathway (1 to 2 percent)
Creates serotonin and melatonin.
Supports mood, sleep, digestion, and calmness.
Tryptophan → 5-Hydroxytryptophan (5-HTP) → Serotonin → Melatonin
2. Kynurenine Pathway (about 90 percent)
This is the immune stress pathway.
Tryptophan → Kynurenine (KYN)
High Kynurenine = inflammation
Low Kynurenine = weak immune activation or low tryptophan
3. Indole-3-Propionic Acid (IPA) Pathway
Powered by your gut bacteria.
Tryptophan → Microbial Breakdown → Indole-3-Propionic Acid (IPA)
High IPA = strong, diverse microbiome
Low IPA = weak microbiome or low fiber intake
IPA vs KYN: What They Reveal
Although there are three pathways, two pathways tell the most about your health:
-
- Indole-3-Propionic Acid (IPA) → Represents gut strength
- Kynurenine (KYN) → Represents immune stress
They compete for tryptophan.
Where your tryptophan goes determines how you feel.
Can IPA and KYN Be High at the Same Time?
Yes.
This means your gut microbiome is strong, but your immune system is stressed.
Common causes:
-
- chronic stress
- autoimmune flares
- infection
- lack of sleep
- high omega-6 intake
- low omega-3 intake
Can IPA and KYN Be Low at the Same Time?
Yes, and it means:
-
- low tryptophan intake
- weak digestion
- long-term stress
- low immune function
- poor microbial diversity
- low fiber intake
This pattern shows the body is not sending tryptophan toward either protection or repair.
Traditional Gut Inflammation Tests Fall Short
Most gut tests only reveal part of the picture:
❌ Calprotectin (Fecal Calprotectin Test) – Detects inflammation only when disease is already present.
❌ C-Reactive Protein (CRP) – A general inflammation marker, not gut-specific.
❌ Zonulin – Linked to gut permeability, but inconsistent and unreliable.
❌ Lipopolysaccharides (LPS) – Hard to test and not standardized.
❌ Biopsy (tissue sample) – Very invasive.
❌ Stool microbiome tests – Show bacteria but not what they are doing.
None of these tests measure:
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- tryptophan pathways
- immune stress signaling
- gut-brain communication
- microbial efficiency
This is why they miss early inflammation.
Why the Gut Health Test I Endorse Is Different
This at-home dried blood spot (DBS) test measures what truly matters:
✔ Indole-3-Propionic Acid (IPA) – gut microbial strength
✔ Kynurenine (KYN) – immune activation
✔ Gut-Brain Signals
✔ Tryptophan Efficiency
✔ Immune Stress Indicators
✔ A Full Gut Health Index
While most gut tests show what is inside your stool, this test shows what your gut is doing to the rest of your body.
How to Improve High Kynurenine (KYN) Naturally
✔ Eat more fiber (beans, lentils, vegetables, fruit, oats)
✔ Add polyphenols (berries, green tea, olives, EVOO)
✔ Balance your omega-3 intake with BalanceOil+
✔ Improve sleep
✔ Reduce stress
✔ Support healthy digestion
Most people see improvements in 90 to 120 days.
How the Gut Health Test Works
-
- Prick your finger
- Place a few drops of blood on the test card
- Mail the card in the prepaid envelope
- The sample is processed by Vitas Analytical Services in Oslo, Norway
- Testing is HIPAA-compliant and anonymous
- Results return in 10–20 business days
Vitas also conducts tests for:
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- Harvard University
- The University of Oxford
- Karolinska Institute
- The National Institutes of Health (NIH)
This ensures the results are accurate and research-grade.
Why You Should Know Your Kynurenine (KYN) Level
Your Kynurenine number reveals:
-
- hidden inflammation
- immune stress
- the strength of your gut barrier
- how your body is using tryptophan
- early signs of chronic health issues
Indole-3-Propionic Acid (IPA) shows gut strength.
Kynurenine (KYN) shows immune stress.
Together, they give the full gut-immune picture.
Next Steps
If this information speaks to you and you want to know what is really going on inside your gut and immune system, the next step is simple.
To learn more about the Gut Health Test, contact the person who shared this article with you, or email me directly at robert@dietfreelife.com.
You can also schedule a free consultation, where we will review your health goals and see if this test and a personalized nutrition plan are a good fit for you.
References
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- Agus, A., Planchais, J., & Sokol, H. (2018). Gut microbiota regulation of tryptophan metabolism in health and disease. Cell Host & Microbe, 23(6), 716–724.
- Badawy, A. A. (2017). Kynurenine pathway of tryptophan metabolism: Regulatory and functional aspects. International Journal of Tryptophan Research, 10, 1–20.
- Patterson, E., Ryan, P. M., Cryan, J. F., Dinan, T. G., Ross, R. P., & Fitzgerald, G. F. (2016). Gut microbiota and the endocrine system. Frontiers in Neuroendocrinology, 44, 50–63.
- Schwarcz, R., Bruno, J. P., Muchowski, P. J., & Wu, H. Q. (2012). Kynurenines in the mammalian brain: When physiology meets pathology. Nature Reviews Neuroscience, 13(7), 465–477.
- Wikoff, W. R., et al. (2009). Metabolomics analysis reveals large effects of gut microflora on mammalian blood metabolites. Proceedings of the National Academy of Sciences, 106(10), 3698–3703.
________
Robert Ferguson is a California- and Florida-based single father of two daughters, clinical nutritionist, Omega Balancing Coach™, researcher, best-selling author, speaker, podcast and television host, health advisor, NAACP Image Award Nominee, creator of the Diet Free Life methodology, and Chief Nutrition Officer for iCoura Health. He also serves on the Presidential Task Force on Obesity for the National Medical Association and the Health and Product Advisory Board for Zinzino, Inc.
🗓️ Schedule a FREE consultation with Robert Ferguson about becoming a client: SCHEDULE FREE CONSULTATION
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