Biomelogic
Public framework audit

Host Capacity Model — Framework Audit

When colonocyte bioenergetic capacity falls, the colonic oxygen gradient destabilises, facultative anaerobes expand, barrier integrity weakens, and downstream immune, mast-cell, and metabolic systems amplify. The Host Capacity Model proposes that in a subset of complex chronic cases — recurrent SIBO, MCAS-pattern symptoms, post-viral gut dysfunction — host substrate capacity is the dominant leverage point, not the microbe.

Last reviewed: 2026-05-12

  • Educational systems-biology consulting · Not diagnosis
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Established biology

Replicated and broadly accepted in the peer-reviewed literature.

  • Butyrate is the primary energy substrate for colonocytes (Donohoe 2011 and replications).
  • Colonocyte β-oxidation maintains physiologic mucosal hypoxia (Byndloss 2017; Litvak/Bäumler 2018).
  • LPS, flagellin, and other PAMPs signal through TLR4/TLR5 to activate innate immunity.
  • Mast cells respond to substrates including IgE, complement, neuropeptides, and microbial products.
  • Mitochondrial dysfunction is documented in post-viral syndromes including post-COVID conditions.

Literature-supported mechanism

Mechanisms described in published literature with less consensus than established biology.

  • Loss of mucosal hypoxia favors expansion of facultative anaerobes (Enterobacteriaceae) — well-supported in animal models.
  • Barrier permeability is associated with low-grade endotoxemia, which can drive mast-cell and systemic inflammatory tone.
  • Recurrent SIBO has documented high relapse rates after antimicrobial-only strategies (Pimentel 2011 and follow-ups).
  • Hydrogen sulfide at elevated concentration inhibits cytochrome c oxidase, providing a candidate biochemical link between dysbiosis and mitochondrial stress.

Host Capacity Model interpretation

Synthesis specific to this framework — reasoned interpretation, not external consensus.

  • These mechanisms can be integrated into a single host-capacity framework where colonocyte bioenergetic state is treated as the upstream substrate for downstream phenotypes.
  • Dysbiosis is reframed as adaptive to a deteriorated host substrate, not a primary disease entity in this subset.
  • MCAS-pattern symptoms and post-viral fatigue are reframed as downstream amplification of upstream substrate failure when no other primary cause is identified.

Hypothesis

Testable proposals not yet sufficiently supported to be treated as established.

  • Many recurrent-SIBO, MCAS-pattern, and post-viral cases share a common host-capacity substrate.
  • Restoring colonocyte bioenergetic capacity is a more durable strategy than repeated antimicrobial cycles in this subset.
  • A subset of pregnancy-loss-history cases may have systems-biology context worth mapping educationally before licensed clinical workup.

Speculative / emerging

Plausibility-level reasoning at the edge of available evidence.

  • Specific quantitative thresholds for clinical sufficiency of colonocyte β-oxidation in humans.
  • Whether host-capacity restoration alone (without microbial modulation) is sufficient in severe cases.
  • Generalisation of the model beyond the gut–immune axis to other organ systems.

Framework Confidence Matrix

Each row is a building block of the Host Capacity Model. Columns show the evidence tier, current confidence, residual uncertainty, the strongest counterargument, the clinical implication, and the role the claim plays in the framework.

  • Colonocyte butyrate oxidation shapes physiologic epithelial hypoxia.

    Established biology
    Uncertainty
    low
    Counterargument
    Other oxygen-consuming processes (e.g., neutrophil activity) could maintain hypoxia independently.
    Clinical implication
    Educational frame for why colonocyte fuel matters.
    HCM role
    Foundational substrate for the host-capacity thesis.

  • Inflammation disrupts epithelial mitochondrial metabolism.

    Literature-supported mechanism
    Uncertainty
    moderate
    Counterargument
    Mitochondrial dysfunction may be downstream of immune signalling rather than mechanistically central.
    Clinical implication
    Justifies considering anti-inflammatory and substrate-supportive context together.
    HCM role
    Connects immune state to bioenergetic capacity.

  • Oxygen-gradient instability favors facultative anaerobes.

    Literature-supported mechanism
    Uncertainty
    moderate
    Counterargument
    Facultative anaerobe expansion may follow rather than cause epithelial dysfunction.
    Clinical implication
    Educational frame for recurrent dysbiosis patterns.
    HCM role
    Microbe-side projection of host-capacity failure.

  • Dysbiosis may be adaptive to host-state change in some cases.

    Mechanistic inference
    Uncertainty
    high
    Counterargument
    In many cases dysbiosis is the primary disturbance, not a downstream signal.
    Clinical implication
    Argues against microbe-only framing in HCM-fit cases.
    HCM role
    Reframes microbial disturbance as a readout of host substrate.

  • MCAS-pattern symptoms may amplify from gut-barrier and metabolite stress.

    Clinical-pattern observation
    Uncertainty
    high
    Counterargument
    MCAS may be a primary mast-cell disorder independent of gut state.
    Clinical implication
    Educational frame for considering gut context in MCAS-pattern cases.
    HCM role
    Explains downstream mast-cell amplification when no primary mast-cell cause is found.

  • SIBO recurrence may reflect unresolved host substrate capacity.

    Clinical-pattern observation
    Uncertainty
    moderate
    Counterargument
    Recurrence may be driven by motility, structural, or dietary factors independent of host bioenergetics.
    Clinical implication
    Educational frame for cases that recur after multiple antimicrobial cycles.
    HCM role
    Central clinical pattern the framework attempts to explain.

  • SIBO, MCAS, and long COVID may share an upstream host-capacity substrate.

    Hypothesis
    Uncertainty
    high
    Counterargument
    The overlap may be explained by shared risk factors or ascertainment bias.
    Clinical implication
    Educational integration in cases that show all three patterns.
    HCM role
    Synthesis-level claim — the most uncertain.

Strongest counterarguments

The objections a careful skeptic should raise first.

  • Dysbiosis may be primary in some cases; treating the microbe first may be sufficient.
  • MCAS may be primarily mast-cell-intrinsic, genetic, structural, or post-trauma — independent of gut state.
  • Post-COVID symptoms may be primarily vascular, neurological, or autoimmune rather than gut-mediated.
  • Some patients durably resolve recurrent SIBO with antimicrobials alone; the model does not explain those cases.
  • Normal stool testing in some cases challenges the centrality of dysbiosis in the framework.
See the full Counterargument Library →

What would weaken or falsify the model

  • A controlled human trial showing durable resolution of recurrent SIBO with antimicrobial-only strategies in cases with documented bioenergetic impairment.
  • A cohort study showing that targeted restoration of colonocyte bioenergetics alone fails to reduce SIBO/MCAS/post-viral burden across reasonable timeframes.
  • Direct human evidence that mucosal hypoxia is preserved despite chronically suppressed colonocyte β-oxidation.
  • Demonstration that the SIBO/MCAS/long-COVID overlap is fully accounted for by shared genetic risk or ascertainment bias.
Scope boundary

Where this model may not apply

The Host Capacity Model is a focused framework with explicit limits. It is not appropriate for the following scenarios, which require licensed clinical care or a different framing:

  • Acute infection requiring medical care.
  • Structural GI disease (strictures, fistulae, neoplasia).
  • Primary immunodeficiency.
  • Symptoms primarily driven by medication.
  • Severe endocrine disorders (untreated thyroid, adrenal, pituitary disease).
  • Pregnancy emergencies and pediatric emergencies.
  • Cases where microbial-directed intervention has produced durable remission.
  • MCAS that appears clearly independent of gut dysfunction.

Alternative explanations

Competing frameworks worth taking seriously.

  • Bile-acid-first models propose bile signaling as the dominant upstream lever.
  • Vagal/autonomic-first models propose autonomic dysfunction as the upstream node.
  • Connective-tissue-first models (hEDS-spectrum) propose tissue laxity as the upstream substrate.
  • Genetic mast-cell disorders propose mast cells themselves as the primary lesion.

Clinical-scope boundaries

  • Biomelogic does not diagnose, treat, prescribe, or guarantee outcomes.
  • All work is educational systems-biology analysis intended to be discussed with the client's licensed medical team.
  • Engagement is declined when a case is outside the model's scope or appears to require urgent clinical care.

Representative citations

Related framework pages

Skeptical FAQ

Hard Questions about this framework

If after reading this audit the framework still seems worth applying to your case:

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