Black 1994.

Study characteristics
Methods	RCT Summary risk of bias: moderate to high
Participants	People with non‐melanoma skin cancer (USA) CVD risk: low Control: randomised 67, analysed 58 Intervention: randomised 66, analysed 57 Mean years in trial: 1.9 % male: control 67%, intervention 54% Age: mean control 52.3 (SD 13.2), intervention 50.6 (SD 9.7) Ethnicity: white 100% (excluded from study if of Asian, Black, Hispanic or American Indian ancestry) Statins use allowed: Unclear % taking statins: Not reported
Interventions	Reduced fat vs usual diet Control aims: no dietary advice Intervention aims: total fat 20%E, protein 15%E, CHO 65%E Control methods: no dietary change, 4‐month intervals clinic examination by dermatologist Intervention methods: 8 x weekly classes plus monthly follow‐up sessions, with behavioural techniques being taught following individual approach (not clear if in a group or individual). 4‐month intervals clinic examination by dermatologist Intervention delivered face‐to‐face by a dietitian Total fat intake, %E ("during study" months 4 ‐ 24): cont 37.8 (SD 4.1), int 20.7 (SD 5.5) (mean difference ‐17.10, 95% CI ‐18.88 to ‐15.32) significant reduction Saturated fat intake, %E ("during study", months 4 ‐ 24): cont 12.8 (SD 2.0), int 6.6 (SD 1.8), (mean difference ‐6.20, 95% CI ‐6.90 to ‐5.50) significant reduction PUFA intake, %E ("during study", months 4 ‐ 24): cont 7.8 (SD 1.4), int 4.5 (SD 1.3), (mean difference ‐3.30, 95% CI ‐3.79 to ‐2.81) significant reduction PUFA n‐3 intake: not reported PUFA n‐6 intake: Linoleic acid, cont 16.9 (SD 5.6) g, int 8.5 (SD 3.3) g MUFA intake, %E ("during study", months 4 ‐ 24): cont 14.4 (SD 1.7), int 7.6 (SD 2.2), (mean difference ‐6.80, 95% CI ‐7.52 to ‐6.08) significant reduction CHO intake, %E ("during study", months 4 ‐ 24): cont 44.6 (SD 6.9), int 60.3 (SD 6.3), (mean difference 15.70, 95% CI 13.29 to 18.11) significant increase Protein intake, %E ("during study", months 4 ‐ 24): cont 15.7 (SD 2.4), int 17.7 (SD 2.2), (mean difference 2.00, 95% CI 1.16 to 2.84) significant increase Trans fat intake: not reported Replacement for saturated fat: CHO and protein (by dietary aims and achievements), main is CHO Style: diet advice Setting: community
Outcomes	Stated trial outcomes: incidence of actinic keratosis and non‐melanoma skin cancer Data available on total mortality? yes Cardiovascular mortality? yes Events available for combined cardiovascular events: cardiovascular deaths Secondary outcomes: cancer deaths (none) Tertiary outcomes: none (weight data provided, but no variance info)
Notes	Study duration 24 months. Study aim was to achieve low‐fat diet, but the study achieved a statistically significant reduction in saturated fat intake in the low‐fat group compared to control. SFA reduction achieved. Total serum cholesterol: not reported At 2 years control ‐1.5 kg n = 50?, intervention ‐1 kg n = 51? Trial dates: Study dates not reported (but still recruiting at first publication in 1994) Funding: National Cancer Institute Declarations of Interest of primary researchers: none stated, all authors worked for academic or health institutions
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"list of randomly generated numbers"
Allocation concealment (selection bias)	Unclear risk	Allocation method not clearly described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Dietary advice provided, so participants not blinded
Blinding of outcome assessment (detection bias) CVD outcomes	Low risk	"examined .... by dermatologists unaware of their treatment assignments". Deaths (all‐cause and CVD) not considered relevant to the intervention
Blinding of outcome assessment (detection bias) All‐cause mortality	Low risk	Blinding is not relevant in assessment of mortality
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low risk for all‐cause and CVD mortality. Unclear for other outcomes
Selective reporting (reporting bias)	Low risk	Not relevant for primary and secondary outcomes as all trialists asked for data
Free of systematic difference in care?	High risk	Minor, all have 4‐monthly clinic visits, the intervention group had 8 behavioural technique classes that the control group did not have
Stated aim to reduce SFA	High risk	Aim to reduce SFA not stated
Achieved SFA reduction	Low risk	Statistically significant SFA reduction achieved
Achieved TC reduction	Unclear risk	Not reported
Other bias	Low risk	None noted