**4. Discussion**

The aim of this study was to develop a FCDB as complete as possible in terms of food, nutrients and other compounds. This is especially important because globally there is a large nutritional data gap [33]. This trend is changing, since according to Finglas et al. [49] many countries are making efforts to create or update their FCDB. Epidemiological studies where several countries are involved, such as the EPIC study, are becoming more and more common. According to Slimani et al. [51] during the EPIC study a total of 26 nutrients for more than 550 foods per country were selected; after appropriate standardization they were used for cross-country comparisons.

Since the S4H project involves several countries, we used the EPIC study as our reference [51]. All the databases were chosen by agreement between coordinators and researchers. The three countries involved in the intervention were used as the main sources for FCT/FCDB [69–71]. The national FCT/FCDB were selected assuming that the most reliable values were available at the local level. Some nutrients were missing from one or more FCDBs. Therefore, we decided to include three more to make ours more representative of European foods [10]. These widely recognized databases were from Italy [72], the Netherlands [26,27] and the United Kingdom, since these countries had more updated versions [81,82]. Finally, four more international FCT/FCDB were included to enrich nutritional composition: the USDA FCDB, since it is widely used [31], the INFOODS/FAO—FCT/FCDB [14,30] to increase the number of nutrients and to take into account the biodiversity of some foods, and, finally, Phenol explorer 3.6 was chosen [73–75] due to the great implication that polyphenols have on diet and health [61]; this allowed for the enhancement of national FCT/CBDT through the addition of more foods and the inclusion of more than 600 bioactive compounds.. We discarded 75% of the foods since quality issues were reported in the estimates when introducing new commercial foods [83], emerging dietary components [61], fortified foods or dietary supplements [84], since these are specific to each country. Recipes and prepared dishes were also not incorporated due to the great variability of preparations in each country [85]. Recipes will be linked from another interconnected database under construction. The national FCDB will input those foods or missing values from the S4H FCDB.
