MeDCIn was developed and validated as an objective tool for assessing the degree of compliance of cafeteria menus with the key points of the MD. According to the results, the MeDCIn total score has a high internal consistency, evidenced by a Cronbach’s alpha coefficient of 0.88 (> 0.80), indicating that the items consistently measure what they are intended to measure [49, 50]. The high inter-rater reliability, evidenced by a Cohen’s Kappa of 0,92 (> 0,75), indicates that the MeDCIn is consistent and reliable, with a high level of agreement between researchers [51]. The results of internal consistency and inter-rater reliability are high, demonstrating that the MeDCIn has reproducibility, which proves its potential to be used by different users to assess the degree of compliance of menus with the key points of the MD.

The menus showed low agreement with the MD, with a wide range of results, ranging from − 7 to 13.5 with an average of 4.65 ± 4.2. These findings are in line with other studies which have reported that university students have a low intake of healthy foods such as vegetables, fruit, pulses, whole grains and dairy products, and a high intake of foods high in fat, sugar, and salt [52] and low adherence to the MD [53].

The subdimension IA - food availability, varied between 1.0 and 7.0 with an average of 4.87 ± 1.2, indicating a moderate availability of foods characteristic of the MD. The item that showed the strongest correlation with the final score is the availability of fresh fruit (r = 0,735). In most indices assessing adherence to the MD, fruit is an important component, as it is the desired dessert in the MD, emphasising its importance in the diet [32,33,34,35,36,37, 54,55,56,57]. To promote fruit, 3 points are attributed if the fruit is present daily, -1,5 points if the fruit is present 3 to 4 times a week, and a penalty of − 1,5 points if 1 to 2 times a week or less (not present). The offer of fresh fruit is one of the factors that most influence the final score of the MeDCIn index. In the subdimension IB - variety and frequency of food offered, fruit showed the strongest correlation with the final score (r = 0,723). Although the presence of fruit is important, its variety and seasonality are also relevant [58]. To improve this tool, it would be important to integrate a new item that considers the varieties of fruit available. This addition aims to promote more diversity but must be considered carefully not to compromise seasonality in menus.

In subdimension IA, the availability of non-starchy vegetables (r = 0.597) is another item that has impact on subdimension IA score. Vegetables are an important part of a sustainable, healthy lifestyle [58] and an important component of the MD [12]. They are mentioned in most of the studies that assess adherence to the MD and constitute its pilar [30, 32,33,34,35,36,37,38, 54,55,56,57, 59, 60]. Therefore, if more than 1 non-starchy vegetables are present daily and not repeated on consecutive days in at least 3 weekdays, the menu is scored with 1 point, while if more than 1 non-starchy vegetable is present daily and not repeated on consecutive days 2 points are attributed to the menu, to emphasise their importance and variety.

The availability of dishes with eggs as the main protein source also positively influences the subdimension IA of this tool (r = 0,495). In Portugal, results from the National Survey on Food and Physical Activity 2015–2016, reveal that eggs have a small contribution to the diet [61]. In Croatia, 78% of adults report consumption of eggs and with a mean intake of 24.9 g/day (one egg approximately weighs 63 g [62]. Data on egg consumption in 2021 shows that Portugal had a higher egg consumption (10.83 kg/capita) than the global average (10.34 kg/capita), but was still far below the European average (13.89), while Turkey and Croatia had an even lower consumption than the global average (9.78 and 8.60) [63] eggs are traditionally regarded as supreme protein source, however, with a major drawback of having a high cholesterol content, however, there occurred a paradigm shift regarding the atherogenic potential of dietary cholesterol, and eggs are gaining in popularity among consumers because they provide choline, vitamin D, lutein and zeaxanthin, etc. Although they are an important part of the MD, they are only mentioned in some studies assessing adherence to the MD [54,55,56,57]. These dishes are typically underrepresented in menus and should be more often considered to promote healthy and sustainable diets [58, 64].

In sub-dimension IA, the availability of whole grains and olive oil (for cooking and seasoning) and the use of seasonal products are difficult to assess in the menus. Nevertheless, the authors considered it relevant to have these items in the tool, to promote its use in meal preparation and its disclosure for consumers in menus. Furthermore, whole grain products are included in some of the indices of MD adherence [33, 37, 38, 55, 57, 60], and olive oil is mentioned in all of them [8, 31, 33,34,35,36,37,38, 54, 55, 57, 60]. In MeDCIn whole grains, nuts, and seeds are positively scored with one point if present respectively, 2 or more times a week and once or more a week to promote the availability of these products in the menus. Seasonal products and Mediterranean dishes and soups aren’t included in these individual MD adherence tools [34], but as a tool to evaluate menus, authors believe relevant to include this information.

The sub-dimention IB - variety and frequency of foods offered, varied between − 8.0 and 6.5, with an average of 0.22 ± 3.4, indicating a limited variety, low frequency of key food groups and high-frequency of food groups that should be limited, which is the factor that most influences the dimension I of the MeDCin (r = 0.97). In this sub-dimension IB, apart from fruit (already mentioned), the use of processed meats is the item that showed the strongest correlation with the score (r = 0,516). According to the IAN-AF 15/16, the consumption of processed meats by the Portuguese population is significant, revealing that 56% of Portuguese regularly consume processed meats [61] and, in Europe, the average processed meat consumption exceeds the recommendations [58]. Although it is part of some typical MD dishes, it must be consumed sparingly due to its association with various health problems, including cardiovascular disease and cancer, and its impact on planetary health [58]. Some indicators measuring adherence to MD also include this item to assess the impact of the diet but as a less favourable component [38, 54, 57, 60]. The MeDCIn scores positively with 1 point for the non-use of processed meats and 0.5 if they are used no more than once a week, while a negative point is attributed if processed meats are used more than once a week. This score aims to raise awareness of the importance of reducing the consumption of these foods, promoting the MD, and contributing to dietary changes towards a healthy diet from sustainable food systems [12, 58, 65].

Also, the offer of sweet desserts showed a moderate correlation with the score (r = 0,513). Like processed meat, average sugar intake in Europe exceeds recommendations and its consumption has a negative impact on health [58] and, is not recommended in MD. It is therefore important to moderate its availability [12, 58, 65]. Some indicators of adherence to the MD also include sugar, but as an undesirable component of the diet [35, 38, 54,55,56,57, 66]. In MeDCIn, sweet desserts are part of the menu no more than 3 times per month they are scored with 1 point and, score 0.5 if present no more than once a week. However, the more frequently they are available on the menu, the higher the negative points attributed (-0.5 for 2 to 3 times a week; -1.5 for more than 3 times a week).

Another item that showed a relevant correlation with the score is the offer of seafood dishes in higher proportion than the meat dishes (r = 0,481). Seafood consumption is associated with a lower risk of cardiovascular disease [67], although, meat consumption is higher than seafood consumption [58, 61]. Fish consumption varies significantly across different Mediterranean countries. Portuguese diet includes a wide variety of fish and seafood with a national average consumption of around 59 kg. In Croatia, fish consumption is also significant, accounting for approximately 20.1 kg per capita per year. In contrast, Turkey’s diet has the lowest consumption with an average of 6.2 kg per capita per year [68, 69]. According to the MD key points, seafood consumption should be encouraged [12]. All MD adherence indices include seafood, although they differ in measurement scale and contribution to the final score [30,31,32,33,34,35,36,37,38, 54,55,56,57, 59, 60, 66]. In MeDCIn, a higher proportion of seafood dishes is scored with 2 points, and − 2 if this item is not fulfilled.

Pulses and other items showed a low correlation with the final score, probably because all menus scored poorly on these items. Pulses have a low footprint and are an important part of a healthy and sustainable diet and, are one of the key food groups in MD, considered one the most important foods as an alternative protein source [58, 70], included in most MD adherence indices [32, 34, 35] and some menu evaluation tools [25]. In the future, if pulses become more available on menus, the MeDCIn could integrate the varieties of pulses, to promote diversity.

The dispersion of the results shows the diversity of the food offered in the different menus analysed. The results also indicate a low degree of compliance between the menus evaluated and the MD, suggesting opportunities for improvement in the menus, especially in the variety and frequency of foods.

The menu served in food service institutions is one of the tools that plays a vital role in the development of healthy eating habits and is a valuable instrument for nutrition education [26, 71,72,73,74]. Vegetables, whole grains, pulses, fruits, nuts and seeds are the basis of the MD. These are also the food items that are less prevailed in the analysed menus, which makes this analysis a valuable tool to evaluate the quality of the food offer and identify opportunities to intervene. The validated menu assessment tool for food services is critical for implementing menus that offer healthier and more sustainable options, contributing to promoting dietary intakes that are adequate, healthy and, sustainable [23, 75].

The MeDCIn tool is relevant because although several indices assess individual adherence to DM, few are dedicated to evaluating menus [21,22,23,24,25,26,