Replacement of saturated with unsaturated fats had no impact on vascular function but beneficial effects on lipid biomarkers, E-selectin, and blood pressure: results from the randomized, controlled Dietary Intervention and VAScular function (DIVAS) study.

Randomized, controlled, parallel-group dietary intervention conducted in Reading, United Kingdom. Participants were nonsmoking men and women aged 21 to 60 years with moderate cardiovascular disease risk.

This randomized 16-week parallel-group trial compared two isoenergetic dietary fat substitutions against a saturated fat-rich control diet. The active regimens replaced saturated fat with either monounsaturated fat (MUFA) or n-6 polyunsaturated fat (n-6 PUFA); the MUFA diet used refined olive oil and olive oil/rapeseed oil blends, while the n-6 PUFA diet used safflower oil, with both unsaturated diets also including hazelnuts to meet target intakes.

Replacing saturated fat with MUFA or n-6 PUFA did not improve vascular function. Flow-mediated dilation changed similarly across groups, with %FMD moving from 5.41 to 5.03 on the SFA diet, 5.81 to 5.74 on MUFA, and 5.86 to 5.78 on n-6 PUFA (P = 0.238). However, substitution improved several cardiovascular risk biomarkers: night-time systolic blood pressure was reduced with MUFA versus SFA (change 2.1 vs 3.8 mmHg, P = 0.019), MUFA lowered plasma E-selectin by 7.8%, and both unsaturated-fat diets attenuated increases in total cholesterol, LDL cholesterol, and TC:HDL ratio (overall diet effects P < 0.001). The authors concluded that replacing saturated fats with unsaturated fats, especially MUFAs, can improve cardiovascular risk markers even though vascular function itself was unchanged.

The intervention was relatively short at 16 weeks and involved a specific UK sample of nonsmoking adults with moderate cardiovascular risk, which limits generalizability. Some per-arm demographic and activity details were not clearly extractable, and the tightly controlled diet design may not reflect usual dietary adherence in practice. The primary vascular endpoint was null despite favorable biomarker changes, so clinical significance remains indirect.