The effects of a high walnut and unsalted cashew nut diet on the antioxidant status of subjects with diagnosed metabolic syndrome

Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2006.Motivation: Metabolic syndrome is a constellation of risk factors predisposing to coronary heart disease (CHD) and is classified as a "disease of modern civilization". Characteristics of the metabolic syndrome include abdominal obesity, increased triacylglycerol (TG) concentrations, increased small dense low-density lipoprotein(LDL) particles, decreased high-density lipoprotein cholesterol (HDL-C), hypertension, insulin resistance, inflammation, glucose intolerance and/or type 2 diabetes mellitus. Subjects with metabolic syndrome may be susceptible to oxidative stress due to their prolonged exposure to elevated glucose levels. A variety of natural antioxidants exists (e.g. glutathione, l3-carotene, vitamin C, polyphenols) that may prevent oxidative damage to biological structures. Nuts are rich sources of unsaturated fatty acids, protein, fibre, micronutrients, phytochemicals and antioxidants. Duet o their high antioxidant content, it can, therefore, be speculated that nuts may play a role in the prevention of oxidative stress in subjects with the metabolic syndrome. Objective: - To investigate the effect of a high walnut and a high unsalted cashew nut diet on the antioxidant status of subjects with metabolic syndrome. Methods: Sixty eight subjects with diagnosed metabolic syndrome (according to the ATP III criteria) were recruited to take part in this parallel, randomized, controlled feeding trial. Subjects were mainly recruited from the North-West University, Potchefstroom Campus and surrounding areas. After a run-in period of three weeks during which the participants followed a prudent diet, subjects were randomly divided into three groups receiving either walnuts or cashew nuts (63- 108g/day)as part of a prudent diet, or continued with the prudent control diet. The intervention was followed for eight weeks. Fasting blood samples were taken at the beginning(after the three week run-in period) and at the end of the intervention. Antioxidant variables including oxygen radical absorbance capacity (ORAC), reduced glutathione (GSH)/oxidized glutathione (GSSG), diacron reactive oxygen metabolites (dRom) were measured at the beginning and the end of the intervention. C-reactive protein (CRP), fibrinogen and plasminogen activator-inhibitor activity (PAI-1a) were also measured as markers of inflammation. The antioxidant capacity and the polyphenol content of the diets and the walnuts and cashew nuts were determined at the end of the intervention. Results: A significant decrease in dRom and significant increases in GSSG, the redox status of glutathione (GSH/GSSG) and ORAC were observed in all three groups from baseline to end. GSH remained unchanged from baseline to end in all three groups. No significant differences in changes in dRom (p = 0.92), GSSG (p = 0.99), GSH/GSSG (p = 0.86), antioxidant capacity (p = 0.10) and GSH (p = 0.34) were observed from baseline to end between groups. The total polyphenol content of the walnut and control diets were similar and significantly higher than the cashew nut diet. The antioxidant capacity of the walnut and cashew nut diets showed a tendency to be higher than the control diet (p = 0.07 and p = 0.06 respectively). CRP, fibrinogen and PAI-1a concentrations did not differ significantly between groups. Conclusion: No significant differences between the groups receiving walnuts, cashew nuts or no nuts were observed in GSH, GSSG, GSH/GSSG, dRom or ORAC. Therefore, there seems to be no beneficial effect of the inclusion of walnuts and cashew nuts in the diet on the antioxidant status of the participants.Master