Blocking Effect of Vitamin C in Exercise-Induced Asthma

Vitamin C supplementation for asthma

“…9 participants had FEV1 decrease >15% on both vitamin C and placebo treatments. 11 participants had >15% FEV1 decrease on placebo but <15% FEV1 decrease on vitamin C (Cohen 1997 Fig. 2).…”

“…Tecklenburg did not publish the paired comparison, nor original data so that the paired t-test could be calculated. Nevertheless, these averages give unpaired t = 1.91, corresponding to P[1-tail] = 0.038, which is conservative, the paired test P-value would be smaller.Thus, three trials included in the review found benefit of vitamin C supplementation against EIB at 5 and 8 minutes after the exercise (Cohen 1997; Schachter 1982), or at the time of maximum fall in FEV1 (Tecklenburg 2007). The three P-values calculated above (0.028, 0.0005, 0.038) can be combined by using the Fisher method (Fisher 1948).…”

“…Thus, three trials included in the review found benefit of vitamin C supplementation against EIB at 5 and 8 minutes after the exercise (Cohen 1997; Schachter 1982), or at the time of maximum fall in FEV1 (Tecklenburg 2007). The three P-values calculated above (0.028, 0.0005, 0.038) can be combined by using the Fisher method (Fisher 1948).…”

“…However, the Cochrane review does not give the results for all of Cohen's 20 participants (Cohen 1997 Fig. 2); Analysis 1.2 gives the results for only the 11 participants who had benefit of vitamin C (Cohen 1997 Table 2). Furthermore, the review presents the average of post-exercise FEV1 values and not the pre-post-exercise difference in FEV1 in analysis 1.2.…”

“…Furthermore, the relative effect calculated by Cohen (Table 2; in %units) is a better measure than the absolute value (in litres/s) because the relative effect adjusts for the great variation in baseline FEV1; the relative decrease in FEV1 is also used in guidelines (Rundell 2009). Cohen reports that the average relative fall in FEV1 is 25% in the placebo period and 5% in the vitamin C period (Cohen 1997 table 2). Because the observations are paired, the paired t-test should be used.…”