Verdict No. 3024 · Search date 2026-09-07 · Methodology v1.0
Single-ingredient oral vitamin C,
does it really help with Attenuation of post-exercise FEV1 decline?
30-Second Summary
C
Evidence Grade C · 54 · Safety caution
Do not import a general asthma, breathing-technique or muscle-soreness verdict.
High oral doses can cause gastrointestinal effects. Trial-specific adverse-event counts remain limited.
What the
research showsGrade C with 54 points. Three double-blind crossover trials totaling 40 participants found a smaller post-exercise FEV1 decline. This tiny surrogate signal is not proof of routine asthma control or fewer exacerbations.
research showsGrade C with 54 points. Three double-blind crossover trials totaling 40 participants found a smaller post-exercise FEV1 decline. This tiny surrogate signal is not proof of routine asthma control or fewer exacerbations.
What the
ads claimClaims of preventing asthma or replacing inhalers exceed the tested outcomes.
ads claimClaims of preventing asthma or replacing inhalers exceed the tested outcomes.
Useful facts when choosing a product
- This verdict concerns single-ingredient oral vitamin C and does not automatically include foods, combinations, or intravenous infusion.
- Trials with different doses, durations, and populations were not treated as interchangeable.
- High oral doses can cause gastrointestinal effects; caution is warranted with stone risk, kidney disease, or iron overload.
Chamgap Semantic Classification Code
Permanent code issued
S.vitamin-c.oral.exercise-induced-bronchoconstriction.reduce.placeboSupplements and nutraceuticals > Vitamin C > Oral > Exercise-induced bronchoconstriction > Reduction claim > Placebo
Permanent semantic code issued and kept separate from general asthma-control claims. The code identifies the intervention and claim; it never contains the evidence grade, score, or safety result.
Exact Claim Classification
These independent facets prevent evidence from different forms, routes, populations, effects, and comparators from being mixed.
| Intervention class | S · Supplement or nutraceutical |
|---|---|
| Canonical ingredient or intervention | Vitamin C |
| Source or part used | Purified nutrient. Feedstock, manufacturing process and country are unverified; plant part is not applicable. |
| Formulation or processing | Single-ingredient ascorbic acid supplement; unverified tablet/capsule, salt and excipient details are flagged by study. |
| Route | Oral |
| Dose | Single500 mg or2 g, or1500 mg/day for two weeks |
| Duration | Single pre-challenge dose or two-week crossover periods |
| Population | Asthmatic participants with documented EIB; mixed paediatric/adult cohorts kept separate |
| Effect or condition | Attenuation of exercise-induced bronchoconstriction and post-exercise FEV1 decline |
| Primary endpoint | Maximum post-exercise FEV1 decline (% or L); symptoms secondary |
| Comparator | Matched crossover placebo; usual-diet measurements are not a separate randomized comparator |
| Duplicate-detection key | vitamin-c|oral|exercise-induced-bronchoconstriction|post-exercise-fev1-decline|crossover-placebo |
Gap Measurement · Verdict 3024 · C 54
What the research actually shows
Participants with documented EIB underwent standardized exercise challenges after acute or short supplementation.
Why this is classified as C (54)
Placebo-controlled FEV1 signals and independence are strengths. A surrogate endpoint, only 40 participants, short exposure, and publication-bias risk cap the grade at C with 54 points.
Counterpoint. An improved symptom score does not establish fewer clinical exacerbations.
Rejudgment record. Independent Codex cross-check — One page, one route, one population, one claim, one principal comparator
Scoring profile behind this grade
| Endpoint | S | Surrogate marker - laboratory or imaging measures |
| Replication | R1 | Single confirmatory trial |
| Independence | I2 | Decisive evidence is publicly or non-profit funded |
| Effect size | E+ | Meets the clinically important threshold |
| Precision | C0 | The confidence interval leaves room for benefit |
The scoring table and the verdict agree (C).
Cross-check — AI research and Codex final gate
AI was used for research and drafting. Blind grading, adversarial audit, and the methodology boundary rules were then reapplied before Codex performed the final evidence, grade, copy, and build checks. If a grade cannot be narrowed, both evidence positions and their reasons are published.
Evidence Table
| Study | Design | Sample | Funding | Endpoint | Result | Weight |
|---|---|---|---|---|---|---|
| Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma | Double-blind placebo crossover | 8 | Specific funder/manufacturer unverified | Postexercise FEV1;prospective hierarchy unverified | Maximum fall−6.4±2.4%vs−12.9±2.4%,P<.05;paired95%CI/dispersion type unverified | Direct physiological signal;very small and short |
| The attenuation of exercise-induced bronchospasm by ascorbic acid | Double-blind randomized crossover | 12 | Unverified | FEV1;prior hierarchy unverified | Fall0.24±.06Lvs.44±.14L,mean±SE;exact pairedCI/P unverified | Early supporting signal;do not merge litres withpercent |
| Blocking effect of vitamin C in exercise-induced asthma | Double-blind placebo crossover | 8 | Unverified | Exercise FEV1 | Nine responders reported;whole-cohort paired effect/CI unverified | Mostly children;selected extension not randomizedconfirmation |
Receipt — 5 References
Of 5 cited sources, 3 had limited original-page access (blocked or summary-only) and were verified via index/summary, marked partial; the rest were verified at the original page. As of 2026-09-07.
Tecklenburg SL, Mickleborough TD, Fly AD, Bai Y, Stager JM. Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma. Respir Med. 101(8):1770–1778. 2007. PMID: 17412579; DOI: 10.1016/j.rmed.2007.02.014.
partialSchachter EN, Schlesinger A. The attenuation of exercise-induced bronchospasm by ascorbic acid. Ann Allergy. 49(3):146–151. 1982. PMID: 7114587.
partialCohen HA et al.. Blocking effect of vitamin C in exercise-induced asthma. Arch Pediatr Adolesc Med. 151(4):367–370. 1997. PMID: 9111435; DOI: 10.1001/archpedi.1997.02170410041005.
partialHemilä H. Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis. BMJ Open. 2013. PMID: 23794586. PMCID: PMC3686214.
checkedVitamin C supplementation for asthma. Cochrane Database Syst Rev. 2013. PMID: 24154977.
checkedResearch and draft: AI used · Cross-check: blind grading and adversarial audit
Final verification and publication gate: Codex · Verification cutoff: 2026-09-07 · Corrections: none
Final verification and publication gate: Codex · Verification cutoff: 2026-09-07 · Corrections: none
Cite this verdict
[Chamgap] Oral Vitamin C for Exercise-Induced Bronchoconstriction—An FEV1 Signal From Only 40 Participants — Evidence Grade C·54. 5 cited sources checked. Source: https://chamgap.com/en/verdicts/sports/oral-vitamin-c-exercise-induced-bronchoconstriction/ · CC BY 4.0CC BY 4.0 — free to use with attribution; do not distort grades, numbers, or verdict meaning.
What this document does and does not do
Chamgap is an information source. It reports what research has and has not confirmed; it does not tell readers what to take or buy. That decision belongs to readers and, when needed, medical or legal professionals. This verdict reflects literature available up to the search date and may change as new research appears. Nothing here is medical advice.