Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “The random number generator in SPSS (Version 7.5) was used to create four groups of equal size and the process was repeated until there was no statistically significant difference between the randomised groups in mean age,years of plucking experience, productivity of the previous plucking season, haemoglobin and ferritin values and prevalence and egg counts of Ascaris, Trichuris and hookworms.” Comment: adequately done
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to permit judgement
Similar baseline characteristics	Unclear risk
Similar baseline outcome measurement	Unclear risk
Blinding of participants and personnel (performance bias)	Low risk	Comment: participants: were not aware of the treatments; personnel: were not aware of the treatments
Blinding of outcome assessment (detection bias)	Unclear risk	Outcome assessors: not described
Incomplete outcome data (attrition bias)	Unclear risk	Comment: insufficient information to permit judgement
Prevention of knowledge of allocated intervention	Unclear risk
Protection against contamination	Unclear risk
Selective reporting (reporting bias)	Unclear risk	Comment: outcomes mentioned in the introduction were reported on in the results but no protocol was available
Other bias	Low risk	Comment: there is no evidence of other bias