Houtsmuller 1979.

Methods	RCT, parallel, (increase LA vs usual diet), 72 months maximum Summary risk of bias: moderate or high
Participants	Adults with newly diagnosed diabetes N: 51 intervention, 51 control (analysed unclear intervention, unclear control) Level of risk for CVD: moderate Male: 56% overall (not stated by intervention arm) Mean age (SD): not reported Age range: not reported Smokers: not reported Hypertension: not reported Medications taken by at least 50% of those in the control group: not reported Medications taken by 20%‐49% of those in the control group: not reported Medications taken by some, but less than 20% of the control group: statins (probably) Location: Netherlands Ethenicity: not reported
Interventions	Type: dietary advice Comparison: omega‐6 vs SFA and CHO Intervention: aims total fat 40% E, 1/3 linoleic acid, CHO 45% E, protein 15% E; methods unclear, surveyed by dietitian. Intervention appears to be delivered by dietitian but no clear details on format or frequency Control: aims SFA 35% E, CHO 50% E, protein 15% E; methods unclear, surveyed by dietitian Dose aims: increase ˜9% E LA (aims imply no LA in control, but paper states LA was 4 × higher in intervention than control, est 3% E control, 12% E intervention, so increase of ˜9% E) Baseline n‐6: unclear Compliance by biomarkers: good, serum total cholesterol significantly reduced in intervention compared to control (−0.47mmol/L, 95% CI −0.76 to −0.18), no significant differences in men, but significant improvements in women from 3 years Compliance by dietary intake: unclear (not reported) Energy intake: not reported Total fat intake: not reported Saturated fat intake: not reported PUFA intake: not reported PUFA n‐3 intake: not reported PUFA n‐6 intake: not reported Trans fat intake: not reported MUFA intake: not reported CHO intake: not reported Sugars intake: not reported Protein intake: not reported Alcohol intake: not reported Duration of intervention: 72 months
Outcomes	Main study outcome: progression of diabetic retinopathy Dropouts: unclear Available outcomes: CHD events (total MI and angina), total cholesterol, TGs (data read off graph), CHD mortality (fatal MI), progression of retinopathy, GTT and insulin (measured but results are reported in figures for a subgroup)
Notes	Study funding: Dutch Heart Foundation Response to contact: attempted but no contact established
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants matched in pairs then randomised
Allocation concealment (selection bias)	Unclear risk	Randomisation method not clearly described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Unclear, though unlikely as dietary advice provided
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of outcome assessors not mentioned
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)	Unclear risk	No protocol or trials registry entry found
Attention Bias	Unclear risk	Unclear as methods unclear
Compliance	Low risk	Compliance good assessed by biomarkers
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