Methods	RCT
Participants	Survivors of Oslo Diet Study who had hyperlipidaemia and high risk of CVD in the 1970s (Norway) CVD risk: moderate (although 25% have CVD) control: No n-3 control, 142 randomised, 117 analysed With n-3 control, 140 randomised, 124 analysed intervention: No n-3 intervention, 139 randomised, 122 analysed With n-3 intervention, 142 randomised, 124 analysed Mean years in trial: 3 % male: 100 Age: control groups median 70 years, intervention groups median 70
Interventions	Reduced fat intake vs usual diet Control aims: usual care (with n-3 capsules or corn oil capsules) Intervention aims: 27-30%E from fat, protein 15-18%, CHO 50-55%E, increase fruit, vegetables, fish, decrease meat, polyunsaturated margarine provided free (with n-3 capsules or corn oil capsules) Control methods: usual care, with either corn oil or omega-3 capsules Intervention methods: dietary advice (30-45 mins initially plus 30 mins follow up at 3 months, then 6 monthly), polyunsaturated margarines provided free, plus either corn oil or omega-3 capsules Total fat intake (at 36 months): low fat 27.6 (sd 5.5), cont 29.5 (sd 5.4)%E Saturated fat intake (at 36 months): low fat 9.2 (sd 3.6), cont 10.5 (sd 3.7)%E Style: diet advice and supplement Setting: community
Outcomes	Stated trial outcomes: CVD Data available on total mortality? yes Cardiovascular mortality? yes Events available for combined cardiovascular events: total MI, verified cardiovascular events Secondary outcomes: cancer deaths and diagnoses, diabetes, total MI Tertiary outcomes: BMI, total, HDL, LDL cholesterol, TG, systolic BP
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	‘randomly assigned’
Allocation concealment (selection bias)	Unclear risk	Randomisation method not clearly described
Blinding (performance bias and detection bias) All outcomes	High risk	Not for dietary intervention.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear, deaths, cancer and CV events are drop-outs, trialists asked for data - unclear if any data missing
Selective reporting (reporting bias)	Low risk	Not relevant for primary and secondary outcomes as all trialists asked for data
Other bias	Low risk
Free of systematic difference in care?	High risk	Additional dietary appointments in the intervention groups. See Control and Intervention Methods in Interventions section of the Table of Characteristics of Included Studies
Free of dietary differences other than fat?	High risk	Also fruit, veg, fish and meat advice. See Control and Intervention Aims in Interventions section of the Table of Characteristics of Included Studies