Comparison 1.

Oral vitamin C vs placebo (single‐dose studies)

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 FEV1 (L) ‐ pre‐exercise challenge	2		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
1.1 Absolute values	2	46	Mean Difference (IV, Fixed, 95% CI)	0.36 [‐0.35, 1.08]
2 FEV1 (L) ‐ post‐exercise challenge	2		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
2.1 Absolute values	1	22	Mean Difference (IV, Fixed, 95% CI)	0.27 [‐0.39, 0.93]
2.2 Absolute change	1	24	Mean Difference (IV, Fixed, 95% CI)	0.13 [‐0.05, 0.31]
3 FVC (L) ‐ pre‐exercise challenge	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
3.1 Absolute values	1	24	Mean Difference (IV, Fixed, 95% CI)	‐0.10 [‐2.62, 2.42]
4 FVC (L) ‐ post‐exercise challenge	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
4.1 Absolute change	1	24	Mean Difference (IV, Fixed, 95% CI)	0.13 [‐0.03, 0.29]
5 PEFR (L/min) ‐ pre‐exercise challenge	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
5.1 Absolute values	1	24	Mean Difference (IV, Fixed, 95% CI)	‐0.40 [‐4.00, 3.20]
6 PEFR (L/min) ‐ post‐exercise challenge	1		Mean Difference (IV, Fixed, 95% CI)	Subtotals only
6.1 Absolute change	1	24	Mean Difference (IV, Fixed, 95% CI)	0.49 [‐0.07, 1.05]