Lima 2014.

Study characteristics
Methods	Individually randomised trial conducted in Fortaleza, the capital of the Ceara state in northeastern Brazil
Participants	Eligibility: children aged 2 months to 9 years Excluded: children with fever > 38 °C or exclusively breastfed Sample: 79 children; 39 in vitamin A group, 40 in control group. Mean age 43.3 months. 57% boys
Interventions	Experimental group: vitamin A 100,000 IU in form of retinol palmitate for children aged < 12 months and 200,000 IU for children aged > 12 months Control group: vitamin E Supplements given at enrolment, 4 months and 8 months
Outcomes	Mean serum retinol levels, growth and adverse reactions to vitamin A
Notes	Infant mortality rate in study area was 35/1000 live births. Primary objective of study was to measure the effect of vitamin A on barrier function of gastrointestinal tract. Study concluded that the prevalence of new parasitic infection, especially with Giardia species, was significantly decreased with vitamin A intervention, suggesting an immune regulatory modulation of this nutrient on parasitic intestinal infections.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Comment: 79 children were randomly selected (using computer‐generated random numbers).
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient detail provided to make a judgement.
Blinding (performance bias and detection bias) Blinding of participants	Low risk	Comment: the parent or guardian of the children, field study team and investigators were blinded to treatment agent.
Blinding (performance bias and detection bias) Blinding of provider	Low risk	Comment: the parent or guardian of the children, field study team and investigators were blinded to treatment agent
Blinding (performance bias and detection bias) Blinding of outcome assessor	Low risk	Comment: the parent or guardian of the children, field study team and investigators were blinded to treatment agent. Indication that blinded field study teams assessed outcomes.
Incomplete outcome data (attrition bias)	Low risk	Comment: after 12‐month follow‐up, 22 children were withdrawn from the study due to: change of address (16), parents or guardians did not co‐operate with the study (5), and had above the median z score for length or height at the time of the study initiation (1). The percentage of participants completing the study at 12 months was 72.2%.
Selective reporting (reporting bias)	High risk	Comment: the objective of study also included reporting of diarrhoea. Authors had reported the overall incidence of diarrhoea in the whole population but the figures were presented in a way that they could not be used in the meta‐analysis.
Other bias	Low risk	Comment: no other apparent bias observed.