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Lactobacillus plantarum 299v and the 3HKYN:KYN Ratio in Depression

The user asks whether Lactobacillus plantarum 299v can increase the ratio of 3-hydroxykynurenine to kynurenine. The assistant confirms based on a 2019 RCT in major depression patients, explains the kynurenine pathway relevance, and provides evidence details and links.

  • I've heard that Lactobacillus plantarum 299v might affect the kynurenine pathway. Can it actually increase the ratio of 3-hydroxykynurenine to kynurenine?

  • Great question! Pillser's research database has direct data on this. Here's what the evidence shows:

    Lactobacillus plantarum 299v and the Kynurenine Pathway

    Yes, there is evidence that Lactobacillus plantarum 299v can increase the ratio of 3-hydroxykynurenine (3HKYN) to kynurenine (KYN).

    A 2019 double-blind, randomized, placebo-controlled trial (n=40) in patients with major depression found:1

    • A significant increase in the 3HKYN
      ratio       in the LP299v group compared to the placebo group.
    • The study also reported that LP299v supplementation decreased kynurenine concentration and improved cognitive functions in these patients.

    This is the only study in Pillser's database currently looking at this specific outcome, and it reported a beneficial (small, statistically significant) effect.2

    Context on the Kynurenine Pathway

    The kynurenine pathway is a key route for tryptophan metabolism. An increase in the 3HKYN

    ratio suggests that LP299v may be shifting kynurenine metabolism toward the 3-hydroxykynurenine branch rather than other branches (e.g., the kynurenic acid pathway). This is thought to be relevant in depression because it can influence neuroinflammatory processes and neurotransmitter balance.

    Summary of Evidence

    FindingDetails
    Studies on this specific outcome1 RCT (n=40)
    EffectBeneficial — significant increase in 3HKYN
    ratio
    Population studiedPatients with major depression
    Year2019

    Bottom Line

    Based on the available evidence, Lactobacillus plantarum 299v does appear to increase the 3-hydroxykynurenine to kynurenine ratio. However, this finding comes from a single small study, so more research would be helpful to confirm the effect.

    For more details, you can check the full research page on Pillser.3

    Footnotes

    1. "Probiotic Lactobacillus Plantarum 299v decreases kynurenine concentration and improves cognitive functions in patients with major depression: A double-blind, randomized, placebo controlled study." (2019, RCT, n=40) — Pillser Research Paper ↩

    2. Pillser research database — Lactobacillus plantarum 299v and Increased 3-Hydroxykynurenine to Kynurenine Ratio ↩

    3. Pillser — Lactobacillus plantarum 299v Overview ↩

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