2. Outcomes: exercise‐induced bronchoconstriction/asthma.
| Vitamin C supplementation versus placebo (exercise‐induced bronchoconstriction/asthma) | |||||
| Outcome | Studies | N | Age | Study ID | Study reported result |
|
Health‐related quality of life |
0 | 0 | — | — | — |
|
Asthma exacerbations |
0 | 0 | — | — | — |
|
FEV1 (L) (change scores) | |||||
| Immediately after exercise | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) |
Schachter 1982 | No significant difference between vitamin C and placebo Vitamin C: mean +0.21 (standard error (SE) ± 0.06) Placebo mean +0.08 (SE ± 0.08) t = 1.46 (P = 0.18) |
| 5 minutes after exercise | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) | Schachter 1982 | No significant difference between vitamin C and placebo Vitamin C: mean ‐ 0.24 (SE ± 0.06) Placebo mean: ‐0.44 (SE ± 0.14) t = 2.13 (P = 0.057) |
| Post‐bronchodilator | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) | Schachter 1982 | Post‐bronchodilator scores significantly better on vitamin C Vitamin C: mean + 0.43 (SE ± 0.12) Placebo mean + 0.22 (SE ± 0.10) t = 3.42 (P < 0.01) |
| FEV1 % drop postexercise |
1 | 8 participants (cross‐over design) | Mean age: 24.5 years (4.8) | Tecklenburg 2007 | A significant advantage in favour of vitamin C Reported maximum % drop in FEV1 postexercise on vitamin C diet was ‐6.4% (95% CI ‐12.0 to ‐0.8%; effect size using omega‐squared (ES) 0.40); indicative of an attenuated EIB response. This was significantly different (P < 0.05) from the maximum drop of ‐12.9% (95% CI ‐18.6 to ‐12.3%) on placebo |
|
PEF (change scores) | |||||
| Immediately after exercise | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) | Schachter 1982 | A significant advantage in favour of vitamin C Vitamin C: mean +0.59 (SE ± 0.16) Placebo mean +0.10 (SE ± 0.25) t = 2.3 (P < 0.05) |
| 5 minutes after exercise | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) | Schachter 1982 | No significant difference between vitamin C and placebo Vitamin C: mean ‐0.73 (SE ± 0.28) Placebo mean ‐0.95 (SE ± 0.40) t = 0.90 (NS) |
| Post‐bronchodilator | 1 | 12 participants (cross‐over design) | Mean age 26 years (± 5) | Schachter 1982 | A significant advantage in favour of vitamin C Vitamin C: mean +0.83 (SE ± 0.26) Placebo mean +0.39 (SE ± 0.29) t = 2.69 (P < 0.05) |
|
Asthma symptoms |
1 | 8 participants (cross‐over design) |
Mean age: 24.5 years (4.8) |
Tecklenburg 2007 | A significant advantage in favour of vitamin C
Reported asa significant improvement (P < 0.05) in mean asthma symptom scores (mean score 6.3; 95% CI 5.8 to 6.8) on the vitamin C diet compared to the placebo diet (mean score 5.8; 95% CI 5.1 to 6.2) |
| Adverse events | 0 | 0 | — | — | — |
*Tecklenburg 2007 used Asthma Quality of Life Questionnaire symptom score component. These data are reported in the table under symptoms.
CI: confidence interval FEV1: forced expiratory volume in one second NS: non‐significant SE: standard error