Longer-term soy nut consumption improves vascular function and cardiometabolic risk markers in older adults: Results of a randomized, controlled cross-over trial.

Background: Soy foods may contribute to the beneficial health effects of healthy plant-based diets on the risk to develop cardiovascular disease (CVD). However, their effects on vascular function have hardly been studied.

Objective: To investigate longer-term effects of soy nut consumption on vascular function and cardiometabolic risk markers in healthy older men and women.

Design: Twenty-three healthy participants (age: 60-70 years; BMI: 20-30 kg/m) participated in a randomized, controlled, single-blinded cross-over trial with an intervention (67 g/day of soy nuts providing 25.5 g protein and 174 mg isoflavones) and control period (no nuts) of 16 weeks, separated by eight weeks wash-out. Adults followed the Dutch food-based dietary guidelines.

Results: No serious adverse events were reported and the soy nut regime was well tolerated. Body weights remained stable during the whole study. A higher protein (3.1 energy percent [En%]) and a lower carbohydrate intake (2.0 En%) was observed during the intervention period. Total fat intake was comparable, but that of saturated (-1.3 En%), cis-monounsaturated (-1.5 En%) and cis-polyunsaturated fatty acids (+1.9 En%) differed. Serum isoflavone concentrations were higher after the intervention as compared with the control period (daidzein: 127.8 ng/mL; 95% CI: 74.3-181.3 ng/mL; p < 0.001 and genistein: 454.2 ng/mL; 95% CI: 266.6-641.8 ng/mL; p < 0.001). Brachial artery flow-mediated vasodilation was 1.48 percent points (pp; 95% CI: 0.08-2.89 pp; p = 0.040) higher following soy nut intake. The carotid artery reactivity response and arterial stiffness did not differ. Serum LDL-cholesterol was lower (0.17 mmol/L; 95% CI: 0.02-0.32 mmol/L; p = 0.027), while HDL-cholesterol and triacylglycerol concentrations were comparable. Mean arterial pressure (MAP) was lower (3 mmHg; 95% CI: 0-6 mmHg; p = 0.035).

Conclusions: Longer-term soy nut intake as part of a healthy diet improved endothelial function, LDL-cholesterol concentrations and MAP levels, suggesting mechanisms by which an increased soy food intake beneficially affects CVD risk in older adults. Registered under ClinicalTrials.gov Identifier no. NCT03627637.