Nordic Dietary Pattern and Cardiometabolic Outcomes: A Systematic Review and Meta-Analysis of Prospective Cohort Studies and Randomized Controlled Trials

Abstract Objectives Nordic dietary patterns may have a role in diabetes management. To inform the update of the European Association for the Study of Diabetes (EASD) clinical practice guidelines, we conducted a systematic review and meta-analysis of Nordic dietary patterns and cardiometabolic outcomes. Methods We searched Cochrane, MEDLINE, and EMBASE through Aug 2019. We included cohort studies of ≥1 y and RCTs of ≥3 wk. Two independent reviewers extracted data and assessed risk of bias. The primary outcome was CVD in cohort studies and LDL-C in RCTs. Secondary outcomes included CHD and stroke in cohort studies and markers of glycemic control, lipids, adiposity, BP and inflammation in RCTs. Data were expressed as relative risks (RR) or mean differences (MD) with 95% confidence intervals (CI). GRADE assessed the certainty of evidence. Results We identified 10 cohort studies in people inclusive of diabetes and 6 RCTs in people with ≥1 risk factor (overweight/obesity, metabolic syndrome, dyslipidemia). Nordic dietary patterns were associated with lower risk of the primary outcome, total CVD (RR, 0.93 [95% CI, 0.88, 0.99]) and CVD mortality (0.83 [0.73, 0.94]), as well as stroke (0.88 [0.79, 0.98]) in cohort studies. Although Nordic dietary patterns did not reduce the primary outcome, LDL-C, in RCTs, there were reductions in other established lipid targets, non-HDL-C (MD, −0.49 mmol/L [95% CI, −0.67, −0.30]) and apo B (0.15 g/L [−0.19, −0.11]), as well as weight (2.10 kg [−3.58, −0.63]), BMI (−0.90 kg/m2 [−1.11, −0.69]), waist circumference (2.22 cm [−3.36, −1.09], diastolic BP (1.78 mmHg [−3.21, −0.35]) and insulin (7.23 pmol/L [−11.88, −2.58]). The certainty of evidence was moderate for the reductions in CVD mortality, established lipid targets, adiposity markers, and insulin and low for all other outcomes. Conclusions Nordic dietary patterns are associated with decreased CVD and reduce cardiometabolic risk factors in people inclusive of or at risk for diabetes. The available data indicate a benefit for people with diabetes with a moderate likelihood that more studies will alter our estimates. (clinicaltrials.gov identifier, NCT04094194) Funding Sources Diabetes and Nutrition Study Group (DNSG) of the EASD, CIHR, Diabetes Canada, Joannah and Brian Lawson Center for Child Nutrition, Connaught Fund, Onassis Foundation.