Article - Adherence to a Mediterranean Diet for 6 Months Improves the Dietary Inflammatory Index in a Western Population: Results from the MedLey Study.

Plain Language Summary

Chronic inflammation is thought to be an underlying cause of many chronic diseases and diet can be used to modulate inflammation. The dietary inflammatory index (DII) is a tool rating an individual’s diet as pro- or anti-inflammatory, with an anti-inflammatory diet (low DII) being associated with a reduced risk of cardiometabolic disease. The aim of this 6-month randomised controlled trial was to evaluate the effect of a Mediterranean diet (MedD), as compared to a typical Australian diet (AusD), on DII and cardiometabolic risk factors in healthy Australians aged 65 years or older. Participants on the MedD significantly decreased their DII and had reductions in F2-Isoprostanes (marker of oxidative stress), triglycerides and systolic BP at 3 months and 6 months as well as improved endothelial function at 6 months. However, changes in DII did not correlate with changes in cardiometabolic risk factors. Evaluation of baseline parameters of both groups combined showed associations of DII with BMI, weight, abdominal fat, HDL and systolic blood pressure, with a lower DII correlating with lower risks. The authors concluded that a MedD decreases the DII which may help reduce the risk of cardiovascular disease.

Expert Review

Reviewer: Karin Elgar

13th Mar 2024

Conflict of interest

None

Take home message

When individuals follow The Mediterranean Diet they are able to reduce their dietary inflammation score.

Evidence category

A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)

Summary review

Introduction

Chronic inflammation is thought to be an underlying cause of many chronic diseases.
The dietary inflammatory index (DII) is a tool for rating an individual’s diet as pro- or anti-inflammatory. A low DII (anti-inflammatory diet) is associated with reductions in cardiometabolic diseases.
The aim of the study was to evaluate the effect of a dietary intervention (Mediterranean diet) on DII and cardiometabolic risk factors in older Australians.

Methods

Randomised controlled trial.
Duration: 6 months.
Participants: 152 healthy Australian men and women aged 65 years or older.
Intervention: Traditional Mediterranean diet (MedD, fortnightly sessions with dietician); control: Habitual Australian diet (AusD)
Outcome measures: DII and energy-adjusted DII (E-DII), blood pressure (BP), anthropometric parameters, endothelial function (measured as flow mediated dilatation, FMD), F2-isoprostanes (F2-IsoP, marker of oxidative stress), inflammatory biomarkers, lipids, glucose, insulin, dietary compliance, cognitive performance.

Results

Over the 4 months, the E-DII decreased by 1.1 points in the MedD group (<0.001), but did not decrease in the AusD group (p=0.21).
Compared to AusD, participants on MedD had reductions in F2-IsoP, triglycerides and systolic BP at 3 months and 6 months; improved endothelial function at 6 months (no p-values given as reported elsewhere).
No associations between changes in DII and changes in cardiometabolic outcomes, independent of whether participants were normal or overweight.
Baseline E-DII scores of both groups combined were divided into tertiles and associations with cardiometabolic parameters evaluated (p-values refer to highest vs lowest tertile):
Higher E-DII was associated with higher BMI (p=0.04); body weight (p<0.0001); hip-to-waist ratio (p=0.001) and abdominal fat (p=0.03).
Lower E-DII was associated with higher HDL cholesterol (p=0.04) and lower systolic BP (p=0.005).
No associations between E-DII and other outcome measures.

Conclusion

The authors concluded that adherence to a MedD reduces dietary inflammation index scores, which may be beneficial for reducing chronic disease risk.

Clinical practice applications

The Mediterranean diet lowers dietary inflammatory index scores. This may, in turn, help reduce risk of cardiometabolic disease.

Considerations for future research

Larger and longer-term trials may confirm whether or not the reduction of DII with a MedD translates into a reduction in measurable inflammation and cardiovascular disease.

Expert reviews are written by nutrition professionals and academics with advanced qualifications to provide a critical appraisal of the article and implications for practice. Each review is peer-reviewed by a member of the NED Editorial Board. Find out more about our NED Expert Reviewers here.

Abstract

Increasing evidence supports that a higher dietary inflammatory index (DII®) score is associated with inflammation and cardiovascular disease (CVD) risk, events, and mortality. This randomized trial sought to determine if a change to a Mediterranean diet resulted in a reduction in the DII score, and then it evaluated the relationship between the DII and cardiometabolic outcomes following the administration of a traditional Mediterranean diet in older Australian adults. A total of 152 Australian adults (mean age 71 ± 5 years) was randomly allocated either a MedDiet (n = 80) or to continue their habitual diet (HabDiet) (n = 72) for 6 months. Diet and cardiovascular outcomes were measured at baseline and 3 and 6 months of the intervention. DII and energy-adjusted DII (E-DIITM) scores were calculated from 3-day weighed food records. There was a significant reduction in the DII score at 2 and 4 months for the MedDiet group (−1.40 ± 0.20 p < 0.001 and −1.47 ± 0.20 p < 0.001, respectively), which was significantly different from the HabDiet group over time (p < 0.001). The HabDiet DII score did not change significantly at the 2 and 4 months timepoints (0.47 ± 0.21 p = 0.35 and 0.54 ± 0.21 p = 0.21, respectively). The improvement in the DII in the MedDiet group was not related to any cardiometabolic outcome. Baseline cross-sectional analyses identified a positive association between the E-DII score and average BMI, body weight, WHR, abdominal adiposity, and SBP, and a negative association with HDL-C. We demonstrate that a MedDiet intervention significantly reduced DII scores compared with a habitual Australian diet in older Australians. This could be beneficial for healthy ageing and the avoidance of chronic disease in Western populations.