Kashefi 2014.

Methods	RCT
Participants	Included: 15 to 18 years of age; had regular menstrual cycles; experienced dysmenorrhoea during the first 3 days of menstrual bleeding; and obtained a score > 4 on the pain VAS Excluded: secondary dysmenorrhoea due to an underlying disease or disorder, and using hormonal medications, birth control pills, or pain relief medications Age: mean age = 17 years Source: high schools in Bojnurd, Iran Location: Iran
Interventions	Group 1: ginger powder (250 mg capsule) (N = 48) Group 2: zinc sulphate (220 mg capsule) (N = 56) Group 3: placebo (lactose capsule) (N = 46) The participants were instructed to take the capsules 3 times a day for 4 days, starting from the day before menstrual bleeding to the third day of menstrual bleeding for 2 consecutive cycles
Outcomes	Severity of the dysmenorrhoea (pain) (VAS scale 10 cm); adverse effects (diarrhoea, headache, and heartburn). Participants completed the VAS every 24 hours during the intervention days for 2 consecutive cycles, collected after each intervention cycle
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Then, 150 participants were randomly assigned to three study groups by using the random table.”
Allocation concealment (selection bias)	Unclear risk	Comment: the study authors did not describe allocation concealment methods.
Blinding (performance bias and detection bias) All outcomes	Low risk	“The capsules were identical in shape, package, and colour, and were coded by the pharmacologist. Neither the researcher nor the participants were informed of the type of ingredient in each capsule.”
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	“A total of 150 participants received intervention. Thirteen participants failed to complete the study. Thus, data from 137 participants were analysed based on the actual treatment received and the available follow up”. Comment: based on the text, the dropout rate was 8.67% (13/150). According to information on the flowchart, the dropout rate was 6.67% (10/150). The study authors did not give any reason for participants lost to follow‐up.
Selective reporting (reporting bias)	Low risk	Comment: the study authors reported a priori outcomes. Adverse events were clearly reported.
Other bias	Unclear risk	“The first group (n=48) received capsules containing zinc sulfate, the second group (n=56) received capsules containing ginger, and the third group (n=46) received placebo capsules.” Comment: there was inconsistency of the number of participants in each group between the study text and flowchart of participants.