Methods	RCT
Participants	People with at least one adenomatous polyp of the large bowel removed (USA) CVD risk: low Control: 1042 randomised, 947 analysed Intervention: 1037 randomised, 958 analysed Mean years in trial: control 3.05, intervention 3.05 % male: control 64%, intervention 66% Age: mean control 61.5, intervention 61.4 (all at least 35)
Interventions	Low fat vs usual diet Control: general dietary guidelines Intervention: total fat 20%E, 18g fibre/1000kcal, 5-8 servings fruit and veg daily Control methods: leaflet, no additional information or behaviour modification Intervention methods: >50 hours of counselling over 4 years, included skill building, behaviour modification, self monitoring and nutritional materials Total fat intake (at 4 years): low fat 23.8 (sd 6.0), cont 33.9 (sd 5.9)%E Saturated fat intake: unclear Style: diet advice Setting: community
Outcomes	Stated trial outcomes: recurrence of polyps, prostate cancer Data available on total mortality? yes Cardiovascular mortality? no Events available for combined cardiovascular events: none Secondary outcomes: cancer diagnoses Tertiary outcomes: weight, total cholesterol
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“randomly assigned”
Allocation concealment (selection bias)	Low risk	Phone call to computer randomisation centre, stratified according to centre
Blinding (performance bias and detection bias) All outcomes	High risk	Outcome assessors blinded, participants not.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear, deaths, cancer and CV events are drop-outs - 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	50 hours behaviour modification in intervention group, not in control. 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	Fibre, fruit and vegetable goals in intervention group