Abstract

AIMS Investigations on the possible effect of the Nordic diet (ND) on the glycemic control and the risk of diabetes have led to inconsistent results. The present study tried to determine the effect of the ND on the markers of blood glucose control using a systematic review and meta-analysis of randomized controlled clinical trials (RCTs). METHODS Predefined keywords were used to search PubMed, ISI Web of Science, Scopus and Google Scholar up to April 2019. The random effects model was used to compute the overall estimates. RESULTS In total, six RCTs with 618 participants (6-26 weeks of follow-up period) were included in the present study. The meta-analysis revealed that the ND might not have a considerable effect on fasting blood glucose levels [weighted mean difference (WMD) = -0.05 mmol/l, 95% CI - 0.13, 0.01, P = 0.112]. In contrast, the analyses showed that the ND significantly reduces serum insulin concentrations (WMD = -1.12 mU/l, 95% CI - 1.84, - 0.39, P = 0.002) and the homeostasis model assessment for insulin resistance (HOMA-IR) (WMD = - 0.34, 95% CI - 0.53, - 0.14, P = 0.001) compared to control diets. The effect on serum insulin levels was sensitive to one of the included studies. This dietary pattern did not significantly affect 2-h post-prandial blood glucose and Matsuda index. CONCLUSIONS Adherence to the ND might improve serum insulin and HOMA-IR levels; however, this effect was not confirmed for other markers of blood glucose control. Future well-designed and long-term clinical trials are highly recommended.