Differences in the interpretation of a modernized Mediterranean diet prescribed in intervention studies for the management of type 2 diabetes: how closely does this align with a traditional Mediterranean diet?

Abstract

Purpose and methods: Adherence to Mediterranean diet (MedDiet) is associated with the prevention and management of type 2 diabetes mellitus (T2DM). However, in intervention studies, there is discordance in the interpretation of a MedDiet. The purpose of this paper was to examine, synthesize, and develop a narrative review, exploring the qualitative differences in the interpretation of a modernized MedDiet prescribed as an intervention in clinical trials for the management of T2DM, and how closely this aligns with a traditional MedDiet. The 'traditional' MedDiet is often described as a dietary pattern high in unprocessed plant foods (fruits, vegetables, legumes, nuts, wholegrain cereals, and olive oil); moderate consumption of wine; low moderate in fish/shellfish; and an infrequent consumption of red meat, animal fats, vegetable oils, and processed foods.

Results and conclusions: Synthesis of the reviewed literature demonstrates considerable variation in the qualitative interpretation of a MedDiet. We also identified inadequate reporting of MedDiet interventions, despite a number of studies referring to their intervention as a 'traditional' MedDiet. The majority of studies emphasized the same key dietary components and principles: an increased intake of vegetables, wholegrains, and the preferential consumption of white meat in substitute of red and processed meat and abundant use of olive oil. However, the reporting of specific dietary recommendations for fruit, legumes, nuts, bread, red wine, and fermentable dairy products were less consistent or not reported. Irrespective of the discordance in the interpretation of a MedDiet, a number of studies included in the present review reported improved glycaemic control and favorable cardiovascular outcomes with adherence to a Mediterranean-style diet. Nevertheless, greater clarity and depth of reporting amongst intervention studies is warranted for the refinement of a modernized MedDiet definition that is distinct from a prudent dietary pattern.

Keywords: Definition; Dietary intervention; Dietary pattern; Mediterranean diet; Randomized control trials; Type 2 diabetes.