Some systems have used practical criteria to decide which nutrients to include. As noted previously, nutrients may be excluded because the nutrient information is not available on the NFP or in the nutrient database used to score foods. For example, trans fat was not included in the NRFI system because it was missing from the USDA nutrient database at the time of development. Publically available nutrient databases do not contain all foods available on the market. The NuVal system used in some supermarkets has gone to great lengths to create and continually update a database of branded food items and has scored more than 40,000 products (Katz, Njike, Rhee, Reingold, & Ayoob, 2010). For some systems, nutrients were excluded because the information does not appear on the NFP, making it difficult to assess the nutrient value for a specific product. There are various types of fiber and these are not separated out on the NFP. Another reason nutrients have been excluded is the lack of an analytical method to obtain the nutrient value of a food. For example, no analytical method exists to differentiate added sugars from the sugars intrinsic to the food. The NuVal system applies glycemic load as a proxy for carbohydrate quality in grain foods and foods with added sugar (Katz, 2007). However, values for glycemic load do not exist in food composition databases and are not readily available for all foods.
The consensus of the ILSI Europe workshop on nutrient profiling was that systems should include either disqualifying (negative) nutrients only or a combination of both disqualifying and qualifying (positive) nutrients (Tetens et al., 2007). There was no consensus on the approach for compensation of disqualifying nutrients with qualifying nutrients, although it was generally believed that qualifying nutrients should not compensate for disqualifying nutrients. The report focused on disqualifying nutrients and suggested that total fat, saturated fat, trans fat, sodium, and sugar should be considered. However, consensus could not be reached on sugar and total fat, and it was suggested that energy should be taken into account instead. The workshop consensus was that nutrient criteria should be based on actual nutrient recommendations rather than dietary guidelines. The report states that "[n]utrient recommendations are scientifically based and independent of dietary habits, variability in consumption, and availability of foods" (Tetens et al., 2007, p. 10).