Study quality
As regards it has been adopted that study inclusion with a high risk of bias can distort the meta-analysis outcomes (25, 27), the Cochrane Collaboration tool was used for evaluating the bias risk. The included studies quality were evaluated by following items: randomization sequence generation; allocation concealment; participants, personnel, assessor and investigator blinding; financial interest by companies and attrition rates. These items were given a rating of high, low, or unclear risk of bias. A randomized controlled trial (RCT) was categorized as having overall high, low or medium risk based on the basic items of allocation concealment, participants and assessor blinding , and reporting of attrition rates (High = High risk of bias for one or more than one key areas, Low = Low risk of bias for all key areas, and Medium = Unclear or low risk of bias for all key areas).