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Tsaban G, Yaskolka Meir A, Rinott E, et al. The effect of green Mediterranean diet on cardiometabolic risk; a randomised controlled trial. Heart. 2020 Nov 23. pii: heartjnl-2020-317802. doi: 10.1136/heartjnl-2020-317802. (Original study)

BACKGROUND: A Mediterranean diet is favourable for cardiometabolic risk.

OBJECTIVE: To examine the residual effect of a green Mediterranean diet, further enriched with green plant-based foods and lower meat intake, on cardiometabolic risk.

METHODS: For the DIRECT-PLUS parallel, randomised clinical trial we assigned individuals with abdominal obesity/dyslipidaemia 1:1:1 into three diet groups: healthy dietary guidance (HDG), Mediterranean and green Mediterranean diet, all combined with physical activity. The Mediterranean diets were equally energy restricted and included 28 g/day walnuts. The green Mediterranean diet further included green tea (3-4 cups/day) and a Wolffia globosa (Mankai strain; 100 g/day frozen cubes) plant-based protein shake, which partially substituted animal protein. We examined the effect of the 6-month dietary induction weight loss phase on cardiometabolic state.

RESULTS: Participants (n=294; age 51 years; body mass index 31.3 kg/m2; waist circumference 109.7 cm; 88% men; 10 year Framingham risk score 4.7%) had a 6-month retention rate of 98.3%. Both Mediterranean diets achieved similar weight loss ((green Mediterranean -6.2 kg; Mediterranean -5.4 kg) vs the HDG group -1.5 kg; p<0.001), but the green Mediterranean group had a greater reduction in waist circumference (-8.6 cm) than the Mediterranean (-6.8 cm; p=0.033) and HDG (-4.3 cm; p<0.001) groups. Stratification by gender showed that these differences were significant only among men. Within 6 months the green Mediterranean group achieved greater decrease in low-density lipoprotein cholesterol (LDL-C; green Mediterranean -6.1 mg/dL (-3.7%), -2.3 (-0.8%), HDG -0.2 mg/dL (+1.8%); p=0.012 between extreme groups), diastolic blood pressure (green Mediterranean -7.2 mm Hg, Mediterranean -5.2 mm Hg, HDG -3.4 mm Hg; p=0.005 between extreme groups), and homeostatic model assessment for insulin resistance (green Mediterranean -0.77, Mediterranean -0.46, HDG -0.27; p=0.020 between extreme groups). The LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio decline was greater in the green Mediterranean group (-0.38) than in the Mediterranean (-0.21; p=0.021) and HDG (-0.14; p<0.001) groups. High-sensitivity C-reactive protein reduction was greater in the green Mediterranean group (-0.52 mg/L) than in the Mediterranean (-0.24 mg/L; p=0.023) and HDG (-0.15 mg/L; p=0.044) groups. The green Mediterranean group achieved a better improvement (-3.7% absolute risk reduction) in the 10-year Framingham Risk Score (Mediterranean-2.3%; p=0.073, HDG-1.4%; p<0.001).

CONCLUSIONS: The green MED diet, supplemented with walnuts, green tea and Mankai and lower in meat/poultry, may amplify the beneficial cardiometabolic effects of Mediterranean diet.

TRIAL REGISTRATION NUMBER: This study is registered under ClinicalTrials.gov Identifier no NCT03020186.

Related DynaMed Topics

Discipline Area Score
Family Medicine (FM)/General Practice (GP) 6 / 7
General Internal Medicine-Primary Care(US) 6 / 7
Special Interest - Obesity -- Physician 5 / 7
Public Health 5 / 7
Cardiology 5 / 7
Endocrine 4 / 7
Comments from MORE raters

Endocrine rater

The key but difficult question to answer is whether these small but statistically significant differences have clinical significance (i.e., differences in clinical outcomes, such as CVD events, development of diabetes, etc). The lower animal protein in green Mediterranean diets and decreased calories in both Mediterranean diets would account for LDL cholesterol and weight differences.

Family Medicine (FM)/General Practice (GP) rater

Many clinicians are aware that the Mediterranean diet is beneficial for health, but will not know that further reduction of animal protein confers an additional benefit that is significant in physical and metabolic parameters. Such a modified Med diet is more closely aligned with the Lancet planetary diet, which has co-benefits for environmental sustainability as well.

Family Medicine (FM)/General Practice (GP) rater

I am a family medicine physician who also sees patients referred for diet and exercise counseling to help minimize cardiovascular risk. Dietary studies are incredibly difficult to conduct. With recruitment at a work site, this study was extremely well conducted -- a 3-arm RCT with oversight of a realistic and feasible intervention. The outcomes revealed a step-wise improvement from the General Healthy Diet to the Mediterranean diet to the Green Mediterranean diet. I hope the researchers continue to follow the participants over time to see whether the healthy changes in diet and cardiovascular markers remain.

General Internal Medicine-Primary Care(US) rater

I find dietary studies tedious, but what one eats is important and does make a difference. And now I know what Mankai is. The devil is in the details of how to make dietary interventions work for people. This is interesting but likely irrelevant to the people for whom I care.

Public Health rater

The feasibility and practicability of this intervention in routine clinical practice is likely quite limited.

Public Health rater

This carefully conducted dietary study shows that green modification to the Mediterranean diet results in additional weight reduction and improvement in metabolic parameters compared to Mediterranean diet alone. The study is small and the results confounded (caloric intake reduced in green Med and weight loss may account for much of the metabolic effect). This may be of interest to those cardiologists focused on dietary measures to reduce risk.

Public Health rater

The study reiterates that continued adherence to life style changes of increased physical activity and reduction in red meat consumption combined with a diet rich in vegetables and dry fruits reduces cardiac risk score. Greater reductions in red meat and processed food in the MED groups may have reduced salt intake compared to the DHG group and this data was not collected or provided. Whether any green plant sources would have the same effect, or whether there is any contribution from the specially prepared green "frozen cubes" is speculative. This study adds to the growing body of evidence that calorie intake reduction with increased physical activity is key to improving health of obese sedentary individuals.
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