An Okinawan-based Nordic Diet Improves Glucose and Lipid Metabolism in Health and Type 2 Diabetes, in Alignment with Changes in the Endocrine Profile, Whereas Zonulin Levels Are Elevated

The Okinawan-based Nordic diet has been developed to improve glucose metabolism. The aim of the present study was to summarize all anthropometric, subjective, and biochemical findings obtained following two different studies investigating this diet. The diet was administered i) as a single breakfast to healthy volunteers and ii) as a 12-week dietary intervention to patients with type 2 diabetes. The degree of satiety, sweet cravings, gastrointestinal symptoms, and health-related quality of life were estimated. Weight and blood pressures of participants were measured, and analyses including circulating levels of inflammatory and metabolic biomarkers, hormones, and short-chain fatty acids (SCFA), and microbial diversity and amount of Enterobacteriaceae in feces, were performed. A single breakfast of the diet increased satiety (P<0.001), improved glucose homeostasis (P<0.001), and lowered levels of glucose-dependent insulinotropic polypeptide (GIP) (P=0.002), compared with a standard breakfast. A 12-week intervention in type 2 diabetes increased satiety and decreased sweet cravings, at the same time as health-related quality of life and gastrointestinal symptoms were improved. There were reductions in body mass index (P<0.001), waist circumference (P<0.001), and levels of glucose (P<0.001), cholesterol (P<0.001), and triglycerides (P=0.009), in alignment with the endocrine profile. These improvements were maintained at follow-up 16 weeks later, along with lower levels of ghrelin (P=0.012), polypeptide YY (P=0.002), and visfatin (P=0.021), compared with the parameters recorded at the study start. Levels of haptoglobin, interleukin-18 and thrombocytes were lowered, whereas some other inflammatory biomarkers were unaffected and zonulin levels elevated. Gut microbiota and SCFAs levels were mainly unaffected. The mechanisms governing the anthropometric and metabolic improvements appear to be mediated through alterations in the endocrine profile, yet not in the gut microbiota.