Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “.participants were randomised by the trial statistician (MS) into two groups”
		Comment: Insufficient information to permit judgement
Allocation concealment (selection bias)	Unclear risk	Quote: “.participants were randomised by the trial statistician (MS) into two groups”
		Comment: Insufficient information to permit judgement
Blinding of participants and personnel (performance bias)	Low risk	Quote: “local pharmacist prepared tablets which were identical in number, colour, size and texture to the ergocalciferol, but contained only sucrose.”
		Comment: Adequately done
Blinding of outcome assessment (detection bias)	Low risk	Quote: “All the primary investigators of the study were totally blinded to the treatment regimen.”
		Comment: Adequately done.
Incomplete outcome data (attrition bias)	Low risk	Comment:
		Group 1: No loss to follow‐up.
		Group 2: 1/50 loss to follow‐up.
Selective reporting (reporting bias)	Unclear risk	Comment: Trial registration not reported. Outcomes specified in the methodology section were reported
Other bias	Low risk	Comment: No other biases detected.