Berger 1997.

Methods	Double‐blind randomised controlled trial. 3‐arm design with individual randomisation.
Participants	176 children, both sexes (91 females (52%)), aged 3.3‐8.3 years (69 months old in average), attending the schools administered by the non‐governmental organization "Fe y Alegria" located in a socio‐economically disadvantaged district of La Paz, Bolivia (altitude of 4000 m above sea level). Inclusion criterion: anaemia (haemoglobin concentration equal to or lower than 144 g/L). No additional exclusion criteria listed. Socioeconomic status not reported.
Interventions	Participants were allocated to one of the following groups: Group 1 (n = 59): children received every Tuesday 3‐4 mg of iron per kg of body weight (approximately 60‐80 mg per week); Group 2 (n = 59): children received a daily dose of 3‐4 mg of iron per kg of body weight, 5 days per week, Monday to Fri. Daily group received 5 times as much iron as weekly; Group 3 (n = 58): children received a placebo, once a week, every Tuesday. Placebo consisted of same tablets without iron. Supplements given to groups 1 and 2 consisted of two types of tablets containing either 20 mg or 36 mg of elemental iron in form of ferrous sulphate. These tablets were used in combination to adjust the dose to the child’s weight Length of the intervention: 16 weeks
Outcomes	Haemoglobin, change in haemoglobin, anaemia, zinc erythrocyte protoporphyrin, adherence.
Notes	Tablets were given to children at school, with clean, boiled water, at mid morning, by trained school assistants, under the supervision of a member of the research team. Same tablets were used for weekly, daily, and same tablets without iron were used for placebo. Non malaria area.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Children were randomly assigned to one of three groups. Method of sequence generation not described.
Allocation concealment (selection bias)	Low risk	Method of concealment not described, but the study reported as double blind.
Blinding (performance bias and detection bias) All outcomes	Low risk	Described as double‐blind trial. Same tablets were used for weekly, daily, and same tablets without iron were used for placebo. Participants: children were not aware of the treatment Personnel: personnel were not aware of the treatment Outcome assessors: not described.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Only one person lost to follow‐up in each group, 3 people total. Dropouts were due to migration of the family out of the area of study
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other sources of bias.