Daily Walnut Consumption Improves Metabolic Syndrome Status in Korean Adults

Abstract

The objective of this study was to investigate the effects of daily walnut intake on changes of metabolic syndrome components. It is 38 weeks long cross-over study with 16 weeks of interventions (45g of walnuts and iso-caloric white bread) and 6 weeks of wash-out period in between. 71 Korean adults with metabolic syndrome were randomly assigned one of two sequences: (1) walnut-control sequence (WCS) and (2) control-walnut sequence (CWS). At each visit (at 0, 16, 22, and 38 weeks), along with five components of metabolic syndrome (waist circumference, blood pressure, levels of HDL-C, triglycerides, and fasting blood glucose), the participants' anthropometric and bioimpedance analysis measurement, HbA1c, CRP, serum levels of total cholesterol and LDL-C were measured. Changes from baseline to each visit were determined by using paired t-test. The mean age was 39.2 years old and 46.5% (n=33) of the participants were women. 47 subjects out of 71 had three metabolic syndrome components, 20 subjects had four, and four subjects had five at baseline. After 16 weeks of walnut consumption, one subject had no risk factors, four subjects had only one metabolic syndrome component, and 19 subjects had two, thus 24 subjects (33%) were reversed back to normal status from metabolic syndrome after walnut consumption. Additional eight subjects also showed decrease of number of metabolic syndrome components compared to baseline (i.e., five components at baseline to three or four after walnut consumption) even though they were still categorized having metabolic syndrome. For each metabolic syndrome component, fasting blood glucose level was decreased after walnut consumption compared to control bread intake (p=0.0001). Subjects in WCS group particularly showed significantly lower fasting blood glucose and HbA1c levels after walnut consumption compared to control bread intake. Participants in CWS group, however showed increment in basal metabolic rate, fat free mass and body protein and reduction of body mass index and body fat percentages after walnut consumption compared to control bread intake. The results suggest that daily walnut consumption for 16 weeks may improve metabolic syndrome status and affect bioimpedance analysis parameters as well.