Methods	Design: RCT
	Unit of randomisation: Individually randomised trial
Participants	Location/Setting: School in the Galle district, Sri Lanka
	Sample size: 821 school children
	Dropouts/withdrawals: 47 out of 821 loss to follow‐up
	Sex: Both male and female children were enrolled
	Mean age: 13.5 years
	Inclusion criteria: Children with Hb level >80 g/L were eligible for the study
	Exclusion criteria: Children suffering from acute or chronic diseases, inflammatory conditions, giving a history of any drug consumption other than paracetamol or antihistamines for minor ailments, currently consuming nutrient supplements or having donated blood or received a blood transfusion within the last 4 months were excluded from the study
Interventions	Intervention (sample size):
	Children were supplemented with two capsules per day containing either:
	Group 1: Iron (50 mg/day) in the form of ferrous fumarate (N = 202)
	Group 2: Zinc (14 mg/day) in the form of zinc sulphate (N = 213)
	Group 3: Combined (iron + zinc) (N = 216)
	Control (sample size):
	Group 4: Placebo made of anhydrous lactose (N = 190)
	Intervention was provided on school days for a duration of 24 weeks
Outcomes	Primary outcomes: Height, weight, BMI, height‐for‐age, weight‐for‐age, stunted, underweight, haemoglobin, serum zinc, serum ferritin
	Secondary outcomes: Not specified
	Timing of outcome assessment: After 24 weeks of intervention
Notes	Study start date: Not specified
	Study end date: Not specified
	Funding source: International Atomic Energy Agency (IAEA‐SRL‐11958)
	Conflicts of interest: Not specified