Benefits of Short-Term (4-Week) Daily Walnut Consumption in Middle-Aged Adults at Risk for Metabolic Syndrome: Outcomes of a Randomized Controlled Trial

Abstract

Background: Epidemiological research has shown that regular walnut (from Juglans regia L.) consumption is associated with a reduced risk of cardiovascular disease (CVD), potentially attributable to their antioxidant and anti-inflammatory properties. The vascular cellular adhesion molecule-1 (VCAM-1), a protein upregulated in CVD, has been previously examined in relation to walnut consumption. However, the clinical findings regarding the effects of walnuts on endothelial function among middle-aged individuals susceptible to metabolic syndrome (MetS) remain inconclusive. Objective: This study examined the effects of daily walnut consumption over a four-week period on cardiometabolic parameters (lipid and glycemic profiles, as well as soluble VCAM-1 levels) and anthropometric measurements in middle-aged individuals with at least one altered MetS parameter and no medication. Methods: In a randomized controlled cross-over trial, 22 eligible Caucasian participants (48.81 ± 4.3 years) were selected and randomly assigned to receive either 45 g of walnuts per day or no walnuts within a controlled diet. There were two 28-day intervention periods, with a one-month washout period in between. Clinical and biochemical evaluations were conducted at the beginning and end of each intervention period. Results: A total of 20 participants completed the intervention and were analyzed, with walnuts being well tolerated. A significant decrease in waist circumference (p = 0.049) and a slight change in fasting blood glucose (p = 0.089) were noted following walnut intake. Conclusions: Short-term (4 weeks) dietary supplementation with walnuts resulted in a statistically significant reduction in waist circumference while not impacting the overall health status of participants. Longer-term studies are necessary to investigate the benefits of daily walnut consumption and its impact on the onset and development of MetS in this age group.

Keywords: Juglans regia; blood pressure; cholesterol; chronic inflammation; dyslipidemia; endothelial function; fasting blood glucose; glycemia; glycemic profile; hypertension; lipid profile; triglycerides; waist circumference.

Figure 1

CONSORT flow diagram for the crossover trial.