Data extraction
The following items were subtracted from the eligible publications by using the standard spreadsheets presented in published RCTs: study characteristics (first author, publishing year and study design), participant characteristics (sample size, age, note about subject, gender, health status) and intervention (type of intervention (study group), duration and dosage). The outcome measures included mean and standard deviation (SD) and changes in serum uric acid at baseline, and the end of the study. If additional details were needed, we contacted study authors. Values reported on mg/dl for serum uric acid were converted to μmol/l by multiplying to 59.48.