The Mediterranean Diet
There is increasing interest in the Mediterranean diet in type 2 diabetes as results of studies such as PREDIMED become available. The Mediterranean diet is characterised by replacing most red meat with fish and poultry, including wine in moderation and plenty of vegetables, legumes, grains, fruit, nuts and olive oil. Impressive evidence from the PREDIMED-Reus trial in diabetes prevention demonstrated a diabetes incidence of 10.1% (5.1–15.1%) in the diet plus olive oil group and 11.0% (5.9–16.1) in the diet plus nuts group compared to 17.9% (11.4–24.4%) in the control group. The EPIC-Interact project also demonstrated a positive effect, where high adherence to the Mediterranean diet was associated with a hazard ratio of 0.88 (0.79–0.97), compared with low adherence, in participants over 50 years of age.
Weight Loss
There have only been two studies examining the use of a Mediterranean diet for weight loss in participants with type 2 diabetes. Both studies favoured the Mediterranean diet for greater weight loss but in one study the Mediterranean diet also had a reduced carbohydrate content which may have had a confounding effect.
Glycaemic Control
Two cross-sectional studies analysing adherence to a Mediterranean diet and Hba1c level have been conducted in Mediterranean populations. In the Campanian Postprandial Hyperglycemia Study (n=901), high diet adherence was associated with significantly lower HbA1c and 2 hour post-meal glucose concentrations (difference: HbA1c 0.9%, CI 0.5–1.2%, P < 0.001; 2-hr glucose 2.2 mmol/l, 95% CI 0.8–2.9 mmol/l, P < 0.001). In the PREDIMED study (n=262), while a trend toward an inverse relationship between diet adherence score and HbA1c was identified, it was not statistically significant. A small cross-over study (n=27) compared 12 weeks on a Mediterranean diet (key foods provided) with 12 weeks on their usual diet. Compared with usual diet, the ad libitum Mediterranean diet resulted in a fall in HbA1c from 7.1% (6.5–7.7) to 6.8% (6.3–7.3) (p=0.012). Finally, newly diagnosed patients were randomised to either a low fat or a Mediterranean diet, and time to initiation of antidiabetic therapy measured. After four years significantly fewer in the Mediterranean diet group (44% c.f. 70%, p< 0.001) had needed to start antidiabetic therapy.
Cardiovascular Risk
Positive results have also been reported for Mediterranean diets and cardiovascular risk. In the Melbourne Collaborative Study, participants of Greek or Italian heritage with diabetes were assessed for level of adherence to a Mediterranean diet and followed for a minimum of ten years. In that time the hazard ratios for CVD mortality per unit of Mediterranean diet score were 0.94 (95% CI 0.89–0.99) in men and 0.94 (95% CI 0.87–1.01) in women. The study found those with higher diet scores had higher intakes of MUFA, fibre, omega 3 fatty acids, fruit and vegetables and lower intakes of saturated fat. Improvements in endothelial function have also been demonstrated in a group with the metabolic syndrome in a study over 2 years of a Mediterranean diet.