Background: Impaired baroreflex sensitivity (BRS) is associated with cardiovascular diseases and the metabolic syndrome. Because lipid abnormalities have been associated with impaired BRS, this study aimed to determine whether diets known to improve the lipid profile, namely a diet high in polyunsaturated fatty acids (walnuts) or monounsaturated fatty acids (cashew nuts), would improve BRS in subjects with metabolic syndrome (MS).
Methods: A controlled feeding trial with a randomized, controlled, parallel study design was undertaken, which involved 62 subjects with MS. Subjects were stratified according to gender and age and were randomized into three groups receiving a control diet, or a diet high (20% energy) in walnuts or unsalted cashew nuts for 8 weeks while maintaining body weight. The BRS, C-reactive protein (CRP), and MS components were measured before and after the intervention.
Results: After the intervention, BRS in the walnut-fed study group decreased (P = .038) and that in the cashew-fed study group increased (P = .036), but the BRS in the control group did not change (P = .56). The percent change of the walnut versus cashew group differed (P = .019). Body mass index, waist circumference, blood pressure, high-density lipoprotein cholesterol, and triacylglycerol did not change. The fasting glucose concentrations of the cashew group increased (P = .03).
Conclusions: The significant improvements in BRS obtained by a diet rich in cashew nuts underline the beneficial cardiovascular effects of nuts. However, the opposite result was obtained with a diet rich in walnuts. These significant changes observed might indicate that BRS is particularly sensitive and influenced by changes in diet without changes in obesity.