Recovering From a Stomach Bug or Post-Antibiotic Gut: A 3-Phase, Day-by-Day Convalescence Protocol

Phase 1 — Rehydrate (hours 0–24, the acute phase) This is where almost all the benefit lives. Diarrheal illness kills through fluid and electrolyte loss, not the pathogen itself.Stack-kit editorial

For an acute stomach bug, the single highest-yield move is reduced-osmolarity oral rehydration solution (245 mOsm/L: 75 mmol/L sodium, 75 mmol/L glucose) — it cuts stool output, vomiting, and the need for IV fluids versus the old WHO formula and versus plain water or sports drinks (Hahn et al., BMJ 2001; WHO/UNICEF 2003). Add Saccharomyces boulardii CNCM I-745 (250–500 mg twice daily, ~10⁹–10¹⁰ CFU), which shortens acute diarrhea by roughly 20 hours and cuts antibiotic-associated diarrhea risk by about half (RR 0.47; McFarland, World J Gastroenterol 2010). Then refeed early with normal food — the BRAT diet is obsolete and slows recovery. Everything below is sequenced by phase, with the popular options that the evidence does not support flagged honestly.

The protocol (by phase)

Phase 2 — Refeed (day 1–3, as vomiting settles) Begin eating within ~4–12 hours of starting rehydration, as soon as you can keep fluids down — do not wait for diarrhea to fully stop.

• Eat a normal, age-appropriate diet. Early refeeding (within 12 h of rehydration) shortened diarrhea and improved nutritional recovery, with no increase in vomiting, persistent diarrhea, or IV-fluid need versus delayed refeeding (Gregorio, Cochrane 2011, CD007296).
• Practical sequencing: start with starches, lean protein, cooked vegetables, soups, yogurt; add fat and fiber back over 24–48 h as tolerated. Routine lactose avoidance is unnecessary for most adults — most non-breastfed patients tolerate normal feeds without dilution or lactose-free substitution (Gregorio 2011).

Phase 3 — Restore (day 3 onward, especially post-antibiotic) If the trigger was antibiotics, this phase matters most; for a viral bug, the gut typically self-restores once you are eating.

• S. boulardii CNCM I-745, continue 250–500 mg 2×/day through and ~1 week past the antibiotic course. AAD RR 0.47 in adults (McFarland 2010); strongest single-strain evidence for the post-antibiotic indication.
• Lactobacillus rhamnosus GG (≥10¹⁰ CFU/day) is a reasonable adjunct, with one honest caveat below.

What to skip (and why)

This is the part most recovery guides get wrong.

• The BRAT diet (bananas, rice, applesauce, toast). Abandoned by the AAP and not recommended — too restrictive, nutritionally inadequate, and it does not speed recovery. A normal diet shortens illness; BRAT delays it (Gregorio, Cochrane 2011; AAP/AAFP guidance, Am Fam Physician 2012).
• Bone broth as a rehydration or "gut-healing" agent. A cup carries roughly 200–600 mg sodium depending on salting — far below an ORS sodium load and uncontrolled in composition, so it is not a rehydration solution. Claims that broth collagen "heals the gut lining" are unsupported: ingested collagen is digested to amino acids like any protein, and there is essentially no clinical trial evidence for bone broth and gut repair (ZOE/Center for Nutrition Studies reviews, 2023). Drink it for comfort and salt, not as therapy.
• L. rhamnosus GG for AAD in adults — weaker than advertised. GG reduced AAD overall (RR 0.49) and significantly in children, but in adults the pooled effect was not statistically significant (6 RCTs, n=863, RR 0.48, 95% CI 0.20–1.15), reaching significance only in the H. pylori eradication subgroup (Szajewska & Kołodziej, Aliment Pharmacol Ther 2015). It helps acute pediatric gastroenteritis duration (−0.85 day; Szajewska 2019), but for adult post-antibiotic recovery, S. boulardii has the stronger data — so we list GG as optional, not primary.
• Glutamine. Evidence is real but narrow: benefit shows up in critical illness and cancer therapy, while trials in otherwise-healthy adults with acute diarrhea show weak or no benefit. Skip it for a routine stomach bug; this is a "specific-population" supplement, not a general recovery aid.

Safety and who should skip

• Anti-motility drugs (loperamide/Imodium) are not for everyone. Avoid entirely if there is fever, bloody/mucoid stool, or suspected C. difficile — they can prolong invasive infection and precipitate toxic megacolon, and are contraindicated with Salmonella, Shigella, Campylobacter, and dysentery (IDSA, Clin Infect Dis 2017). Loperamide is appropriate only for immunocompetent adults with non-bloody, non-febrile watery diarrhea, and should be stopped if symptoms persist beyond 48 hours.
• See a clinician — do not self-treat at home — if: signs of severe dehydration (no urination 8+ hours, dizziness on standing, sunken eyes), blood in stool, fever above 39 °C / 102 °F, diarrhea lasting more than ~7 days, severe abdominal pain, or you are pregnant, immunocompromised, over 65, or have inflammatory bowel disease.
• S. boulardii is a live yeast. Do not use it in immunocompromised patients, those with central venous catheters, or the critically ill — rare fungemia has been reported in these groups. Handle capsules away from a catheter line.
• Zinc — the pediatric/adult split. WHO recommends 20 mg/day zinc for 10–14 days for children with acute diarrhea (10 mg for infants under 6 months); it shortens illness by roughly half a day (Lazzerini, Cochrane 2016). This is a malnutrition-context intervention, and the same benefit is not established in well-nourished adults — we do not recommend routine adult zinc here. Note zinc can itself trigger vomiting at higher doses.
• Talk to your provider before adding supplements if you take immunosuppressants or have a catheter, and confirm any antibiotic interaction concerns directly.

How we'd buy it

By spec, brand-agnostic — match these and the label, not the marketing.

• Oral rehydration solution: buy a product that states the reduced-osmolarity / WHO formula on the label (~245 mOsm/L; ~75 mmol/L sodium). Single-serve powder sachets you reconstitute in a measured volume of water are the most reliable; pre-mixed "hydration" drinks are acceptable only if the sodium content actually approaches ORS levels — most flavored electrolyte powders do not.
• S. boulardii CNCM I-745: look for the named strain "CNCM I-745" on the label (this is the studied strain), 250 mg per capsule, dosed to 250–500 mg twice daily. Third-party verification (USP Verified or NSF) is the quality signal; probiotics are not NSF Certified for Sport, so do not expect that mark here.
• L. rhamnosus GG (optional): a product stating strain "GG" (ATCC 53103) at ≥10 billion CFU/serving, with a guaranteed-through-expiry CFU count, not "at time of manufacture."
• Zinc (pediatric use, under clinician guidance): 20 mg elemental zinc as sulfate or gluconate, ideally USP Verified.

Funded by the links you use — never by paid placement. Because we sell no house supplement, we can tell you to skip the broth, the glutamine, and the adult zinc.

Citations

1. Hahn S, Kim Y, Garner P. Reduced osmolarity oral rehydration solution for treating dehydration due to diarrhoea in children: systematic review. BMJ 2001;323:81–85. — Reduced-osmolarity ORS lowered stool output, vomiting, and IV-fluid need vs. standard ORS.
2. WHO/UNICEF. Oral rehydration salts: production of the new ORS (2006); reduced-osmolarity formula adopted 2003 — Na⁺ 75, glucose 75, K⁺ 20, citrate 10, Cl⁻ 65 mmol/L; 245 mOsm/L.
3. McFarland LV. Systematic review and meta-analysis of Saccharomyces boulardii in adult patients. World J Gastroenterol 2010;16(18):2202–2222. — Adult AAD RR 0.47 (95% CI 0.35–0.63).
4. Feizizadeh S, Salehi-Abargouei A, Akbari V. Efficacy and safety of Saccharomyces boulardii for acute diarrhea. Pediatrics 2014;134(1):e176–e191. — Diarrhea duration reduced by ~19.7 h.
5. Gregorio GV, Dans LF, Silvestre MA. Early versus delayed refeeding for children with acute diarrhoea. Cochrane Database Syst Rev 2011, CD007296. — Early refeeding shortened illness; no increase in vomiting/persistent diarrhea; routine lactose-free feeds unnecessary.
6. AAP / King CK et al. Managing acute gastroenteritis; AAFP, Am Fam Physician 2012;85(11):1066–1070. — BRAT diet not recommended; resume normal diet.
7. Szajewska H, Kołodziej M. Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults. Aliment Pharmacol Ther 2015;42(10):1149–1157. — Overall RR 0.49; adults non-significant (RR 0.48, 95% CI 0.20–1.15).
8. Szajewska H, et al. L. rhamnosus GG for treating acute gastroenteritis in children — 2019 update. Aliment Pharmacol Ther 2019. — Duration reduced ~0.85 day.
9. Lazzerini M, Wanzira H. Oral zinc for treating diarrhoea in children. Cochrane Database Syst Rev 2016. — WHO 20 mg/day; ~0.5 day shorter in children >6 months; pediatric/malnutrition context.
10. Shane AL, et al. (IDSA). Clinical practice guidelines for infectious diarrhea. Clin Infect Dis 2017;65(12):e45–e80. — Anti-motility agents contraindicated with fever, bloody stool, or invasive pathogens.

Affiliate disclosure

Stack-kit earns affiliate commission on the brand-agnostic product recommendations above. We do not sell our own supplements, and we have no house brand. We recommend by spec — named strain, dose, and third-party verification — not by commission rate, and we name what to skip (bone broth, glutamine, routine adult zinc) precisely because we have nothing to sell you there.