The use of indexes evaluating the adherence to the Mediterranean diet in epidemiological studies: a review

The purpose of this paper is to review some of the methods that several epidemiological studies use to evaluate the adherence of a population to the Mediterranean diet pattern. Among these methods, diet indexes attempt to make a global evaluation of the quality of the diet based on a traditional Mediterranean reference pattern, described as a priori, general and qualitative. The Mediterranean diet indexes, hence, summarise the diet by means of a single score that results from a function of different components, such as food, food groups or a combination of foods and nutrients. The reviewed evaluation methods can be classified into three categories depending on the way they are calculated: (1) those based on a positive or negative scoring of the components, (2) those that add or substract standardised components, and (3) those that are based on a ratio between components. Dietary scores have been used to explore the multiple associations between the Mediterranean diet, as an integral entity, and health parameters such as life expectancy or the incidence of obesity, cardiovascular diseases and some types of cancers. Moreover, these indexes are also useful tools to measure food consumption trends and to identify the involved factors, as well as to develop comprehensive public health nutrition recommendations. A more precise and quantitative definition of the Mediterranean diet is required if the adherence to such a dietary pattern is intended to be more accurately measured. Other aspects of the Mediterranean diet indexes should also be taken into account, like the inclusion of typical Mediterranean foods such as nuts and fish and the validation of the dietary pattern approach by using biomarkers.