Metabolic Syndrome Systematic Literature Review
Reference: Godos, J., et al., Adherence to the Mediterranean diet is inversely associated with metabolic syndrome occurrence: a meta-analysis of observational studies. Int J Food Sci Nutr, 2017. 68(2): p. 138-148.
One-sentence summary: The Mediterranean diet was inversely associated with metabolic syndrome, although the data are limited and come mostly from cross-sectional studies.
Study type: A systematic literature review and meta-analysis of 12 observational studies (8 cross-sectional and 4 prospective studies).
Diet: Adherence to a Mediterranean diet defined through scores that estimated the conformity of the dietary pattern of the studies population with the traditional Mediterranean dietary pattern.
Outcomes measured: Occurrence or risk of metabolic syndrome.
Population: 7 studies were conducted in Mediterranean countries and 5 in non-Mediterranean countries (Iran = 2, USA = 2, Poland = 1). 10 studies were in healthy populations, with 1 study in those with a high CVD risk and 1 conducted in diabetics.
- Metabolic syndrome: The highest adherence to a Mediterranean diet was associated with a 19% decreased risk compared to the lowest adherence (RR: 0.81, 95%CI: 0.71, 0.92) (12 studies).
- The protective association was found in both cross-sectional and prospective studies.
- Individual components of the Metabolic syndrome (4 studies): High adherence to the Mediterranean diet:
- Reduced the risk of high waist circumference (RR = 0.82, 95%CI 0.70, 0.96).
- Reduced the risk of high blood pressure (RR = 0.87, 95%CI 0.77, 0.97).
- Reduced risk of low HDL-C levels (RR = 0.87, 95%CI 0.77, 1.00).
- Null results for triglycerides.
- Null results for blood glucose.
Quality assessment: The quality of all studies was assessed according to the Newcastle–Ottawa quality assessment scale and all studies scored high quality.
- All studies were observational, precluding a causal relationship.
- There was evidence of heterogeneity across the studies.
- There were different dietary scores used to evaluate the adherence to the Mediterranean diet, which may introduce bias.
- Individuals labelled as “highly adherent” to the Mediterranean diet may still have very different dietary patterns with respect to food groups, depending on their geographical region.
The bottom line: A Mediterranean dietary pattern was associated with a 19% reduced risk of Metabolic syndrome, but the available evidence is limited, coming mostly from cross-sectional studies. More research from prospective cohorts and clinical trials are required to better understand the association.
Garcia, M., et al., The Effect of the Traditional Mediterranean-Style Diet on Metabolic Risk Factors: A Meta-Analysis. Nutrients, 2016. 8(3): p. 168.
Ahluwalia, N., et al., Dietary patterns, inflammation and the metabolic syndrome. Diabetes Metab, 2013. 39(2): p. 99-110.
Esposito, K., et al., Mediterranean diet and metabolic syndrome: an updated systematic review. Rev Endocr Metab Disord, 2013. 14(3): p. 255-63.
Kastorini, C.M., et al., The effect of Mediterranean diet on metabolic syndrome and its components: a meta-analysis of 50 studies and 534,906 individuals. J Am Coll Cardiol, 2011. 57(11): p. 1299-313.
Serra-Majem, L., B. Roman, and R. Estruch, Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutr Rev, 2006. 64(2 Pt 2): p. S27-47.