On 2017 Mar 19, Harri Hemila commented:

Two unpublished trials bias the conclusions on vitamin C and atrial fibrillation

In their meta-analysis on vitamin C and postoperative atrial fibrillation (POAF), Polymeropoulos E, 2016 state that “no significant heterogeneity was observed among [nine] included studies” (p. 244). However, their meta-analysis did not include the data of 2 large US trials that found no effect of vitamin C against POAF and have thus remained unpublished. If those 2 trials are included, there is significant heterogeneity in the effects of vitamin C. Vitamin C had no effects against POAF in 5 US trials, but significantly prevented POAF in a set of 10 trials conducted outside of the USA, mainly in Iran and Greece, see Hemilä H, 2017 and Hemilä H, 2017. Although the conclusion by Polymeropoulos E, 2016 that vitamin C does have effects against POAF seems appropriate, the effect has been observed only in studies carried out in less wealthy countries.

On 2017 Mar 19, Harri Hemila commented:

Two unpublished trials bias the conclusions on vitamin C and atrial fibrillation

In their meta-analysis on vitamin C and postoperative atrial fibrillation (POAF), Polymeropoulos E, 2016 state that “no significant heterogeneity was observed among [nine] included studies” (p. 244). However, their meta-analysis did not include the data of 2 large US trials that found no effect of vitamin C against POAF and have thus remained unpublished. If those 2 trials are included, there is significant heterogeneity in the effects of vitamin C. Vitamin C had no effects against POAF in 5 US trials, but significantly prevented POAF in a set of 10 trials conducted outside of the USA, mainly in Iran and Greece, see Hemilä H, 2017 and Hemilä H, 2017. Although the conclusion by Polymeropoulos E, 2016 that vitamin C does have effects against POAF seems appropriate, the effect has been observed only in studies carried out in less wealthy countries.