Two pathways — two tools
Antibiotic gut damage splits cleanly into two mechanistic pathways that respond to different interventions.
What it is: Selective killing of SCFA-producing commensals → butyrate deficit → barrier degradation → gram-negative LPS expansion.
What addresses it: Probiotics reseed depleted commensals. Prebiotic fibre (inulin, resistant starch, beta-glucan) provides the substrate they need to rebuild butyrate production.
Evidence strength: Strongest evidence base for antibiotic gut support. LGG: ~42% AAD reduction, ~60% C.diff reduction. S. boulardii: similar effect size, yeast-based so survives antibiotic courses.
What it is: Direct epithelial irritation from antibiotic compounds + NF-kB activation from gram-negative LPS + EGFR/ERK repair suppression.
What addresses it: Quercetin inhibits NF-kB via IκB stabilisation — reducing the inflammatory cascade from LPS that probiotics cannot address. Glabridin activates EGFR/ERK — directly stimulating mucosal cell regeneration in the gastric and intestinal lining.
Why probiotics alone are insufficient here: Probiotics rebuild the bacterial community. They do not inhibit NF-kB or activate EGFR/ERK. These mechanisms require direct pharmacological action, not bacterial reseeding.
Probiotics — the microbiome component
The most studied probiotic for antibiotic-associated gut protection. Meta-analysis evidence: ~42% AAD reduction, ~60% C.diff-associated diarrhoea reduction. Gram-positive bacteria — take 2 hours apart from antibiotic doses. Continue 8–12 weeks after course.
A yeast probiotic, not a bacterium — unaffected by antibacterial drugs. Can be taken at the same time as antibiotics (unlike bacterial probiotics). Similar evidence base to LGG for AAD and C.diff prevention.
Prebiotic fibre — the substrate
Probiotics are only as effective as the substrate available to support them. Inulin, fructooligosaccharides (FOS), beta-glucan, and resistant starch feed the Bifidobacterium and Lactobacillus populations being reseeded — accelerating their population rebuilding and butyrate production. A diet rich in prebiotic foods (oats, legumes, onions, garlic, bananas, and underripe fruits) during and after antibiotic treatment provides this substrate naturally. For patients with antibiotic-related GI sensitivity, gradual reintroduction avoids the gas-producing paradox of feeding recovering bacteria too quickly.
Zinc carnosine — an intermediate option
Zinc carnosine has evidence for gastric mucosal repair and some NF-kB modulation — particularly in H. pylori gastritis models. It is less potent than flavonoid-based approaches for NF-kB inhibition and does not directly activate EGFR/ERK. A reasonable consideration for patients who cannot access flavonoid formulations, with the caveat that zinc supplement timing matters during antibiotic courses (fluoroquinolones and tetracyclines bind zinc — take 2 hours apart).
TumGard — the mucosal component
NF-kB inhibition (quercetin, 700mg): Inhibits NF-kB from gram-negative LPS — the pathway that probiotics cannot address. Reduces the inflammatory cytokine cascade that causes mucosal damage, motility disruption, and EGFR/ERK suppression during antibiotic dysbiosis.
EGFR/ERK mucosal repair (glabridin): Directly activates mucosal cell regeneration in gastric and intestinal lining. Runs on a 60–90 day repair cycle — independent of and complementary to the microbiome recovery timeline.
H. pylori urease inhibition (quercetin + myricetin): Specifically relevant for H. pylori eradication patients — reduces urease activity and thus ammonia-mediated mucosal damage during the antibiotic course that will also be collapsing the microbiome.
H. pylori eradication — the full protocol
H. pylori eradication triple therapy activates: (1) existing H. pylori mucosal damage (focal, gastric, NF-kB, EGFR/ERK suppressed), (2) direct mucosal irritation from metronidazole + clarithromycin/amoxicillin, and (3) broad-spectrum microbiome collapse. All three mechanisms simultaneously. The complete protocol: probiotics (LGG or S. boulardii) during the course and 8–12 weeks after; prebiotic fibre throughout; TumGard from day 1 of the course and continue for 60–90 days post-eradication for gastric mucosal repair.
Protocol by timing
S. boulardii: any time. LGG: 2 hours from antibiotic doses. TumGard: any time, no antibiotic interaction. Prebiotic fibre: with meals, gradual introduction. Avoid high-dose mineral supplements at antibiotic dose times.
Days 1 to end of courseContinue LGG (no timing restriction now — no antibiotic doses). Continue S. boulardii if used. Increase prebiotic fibre gradually as microbiome sensitivity decreases. Continue TumGard daily. Reintroduce fermented foods (yoghurt, kefir) if tolerated.
Weeks 1–4 after courseContinue probiotics until 8–12 weeks post-course. Continue prebiotic fibre throughout. Continue TumGard for 60–90 day repair cycle total from course start. H. pylori eradication patients: TumGard for full 90 days post-eradication.
Weeks 4–12 after courseReferences
- Szajewska H et al. Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children. Alimentary Pharmacology & Therapeutics. 2015;42(10):1149–1157. PMID 26365980. Meta-analysis providing the ~42% AAD reduction and ~60% C.diff reduction evidence for LGG — the strongest probiotic evidence cited in this guide.
- Thursby E, Juge N. Introduction to the human gut microbiota. Biochemical Journal. 2017;474(11):1823–1836. PMID 28512250. Defines the prebiotic substrate requirements for SCFA-producing commensals — basis for the prebiotic fibre recommendation.
- Ye YN et al. Licorice flavonoids and gastric mucosal repair via EGFR/ERK pathway. Journal of Ethnopharmacology. 2023;302:115866. PMID 36842733. Glabridin EGFR/ERK activation — the mucosal repair mechanism that probiotics cannot address.
- Xiao ZP et al. Quercetin as inhibitor of H. pylori urease and NF-kB pathway. European Journal of Medicinal Chemistry. 2006;41(4):476–82. PMID 16887239. Quercetin NF-kB inhibition and urease inhibition — the two mucosal support mechanisms most relevant for antibiotic and H. pylori eradication patients.