Houtsmuller 1979.

Study characteristics
Methods	RCT Summary risk of bias: moderate to high
Participants	Adults with newly‐diagnosed diabetes (the Netherlands) CVD risk: moderate Control: 51 randomised, unclear how many analysed (all analysed re deaths) Intervention: 51 randomised, unclear how many analysed (all re deaths) Mean years in trial: unclear (max duration 6 years) % male: 56% overall Age: mean unclear Baseline total fat intake: unclear Baseline saturated fat intake: unclear Ethnicity: not stated Statins use allowed? Unclear % taking statins: Not reported (probably none as too early, pre‐1980)
Interventions	Modified fat vs usual diet Control aims: SFA 35%E, CHO 50%E, protein 15%E Intervention aims: total fat 40%E, 1/3 linoleic acid, CHO 45%E, protein 15%E Control methods: unclear, surveyed by dietitian Intervention methods: unclear, surveyed by dietitian Intervention appears to be delivered by dietitian but no clear details on format or frequency Total fat intake: not reported Saturated fat intake: not reported (mean difference unclear) PUFA intake: not reported PUFA n‐3 intake: not reported PUFA n‐6 intake: not reported MUFA intake: not reported CHO intake: not reported Protein intake: not reported Trans fat intake: not reported Replacement for saturated fat: mainly PUFA (based on dietary aims) Style: diet advice? Setting: community
Outcomes	Stated trial outcomes: progression of diabetic retinopathy Data available on total mortality? no Cardiovascular mortality? no Events available for combined cardiovascular events: total MI and angina Secondary outcomes: total cholesterol, TGs (data read off graph), CHD mortality (fatal MI), CHD events (MI, angina)
Notes	Study duration 6 years. Study aim was for control group to take 35%E as saturated fat, and the intervention group 40%E from fat, of which 33% was from linoleic acid (so saturated fat < 27%E), but saturated fat intake during trial not reported SFA reduction aimed (unclear whether achieved). Total serum cholesterol, difference between intervention and control, mmol/L: ‐0.47(95% CI ‐0.76 to ‐0.18), statistically significant reduction Trial dates: Study recruitment 1973 to (unclear) Funding: Dutch Heart Foundation 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	Participants matched in pairs then randomised
Allocation concealment (selection bias)	Unclear risk	Allocation method not clearly described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Unclear, though unlikely as dietary advice provided
Blinding of outcome assessment (detection bias) CVD outcomes	Unclear risk	Blinding of outcome assessors not mentioned
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	Unclear risk	Unclear, deaths, cancer and CV events are dropouts, trialists asked for data ‐ unclear if any data missing
Selective reporting (reporting bias)	Low risk	Not relevant for primary and secondary outcomes as we asked all trialists for data
Free of systematic difference in care?	Unclear risk	Level and type of intervention unclear. See control and intervention methods in the Interventions section of the table of Characteristics of included studies
Stated aim to reduce SFA	Low risk	Aim to reduce SFA stated
Achieved SFA reduction	Unclear risk	SFA intake not reported
Achieved TC reduction	Low risk	Statistically significant TC fall
Other bias	High risk	Some concerns around fraud in the first authors later research on diet in cancer. No allegations found regarding his research in diabetes (but much information is in Dutch). Numbers of events are not clear by arm and assumed from adding across various publications