Table 2.

Assessing risk of bias of the included studies by validated Jadad 5-point scale

Author	Publication year	Country	Sample size (n)	Study Design	Randomization (0–2 points)	Double-blind (0–2 points)	Drop-outs and withdrawals (0–1 points)	Jadad score
Sprague [27]	2003	USA	263	multicenter, double-blind, parallel	1	2	1	4
Gafor [26]	2009	Malaysia	25	single-center, open-labelled, parallel	1	0	1	2
Lund [25]	2010	USA	18	single-center, double-blind, crossover	1	2	1	4
Hansen [24]	2011	Denmark	86	multicenter, open-labelled, crossover	2	0	1	3
Ong [23]	2013	Malaysia	66	multicentre, open-labelled, parallel	1	0	1	2
Jamaluddin [22]	2014	Malaysia	26	single-center, open-labelled, parallel	1	0	1	2
Akizawa [21]	2015	Japan	255	multicenter, double-blind, parallel	1	2	1	4
Veceric [28]	2016	Slovenia	20	single-center, open-labelled, parallel	1	0	0	1