Nutrient density is typically defined as the nutrient amount per kcal (or some multiple of kcal, for example, 100 kcal). A nutrient density score is a summation of nutrient values per kcal amount in relation to the daily recommended intake value of each nutrient. Some have suggested expressing nutrient density-based algorithms on a weight basis (i.e., per 100 gram or per serving size) as an alternative to per kcal amount (Drewnowski, Maillot, & Darmon, 2009). Various nutrients can be included that characterize the overall nutritional quality of a food. An advantage of this type of system over a threshold-type system is that it does not assign arbitrary thresholds to determine a score.
Using an overall score of nutrient density, potential modifications to test included the following:
- unit basis (e.g., per 100 kcal or per RACC serving)
- nutrients (e.g., include a fat-quality indicator such as saturated fat as a percentage of total fat, with or without added sugars)
- weighting (e.g., assigning more weight to negative nutrients as positive nutrients)
- bioavailability (e.g., protein quality score, adjustment for nonheme iron that is less well absorbed)
- overall score or food category-specific (e.g., categorize final score into two [healthy or not] or three [low, medium, high] categories using one set of cutoffs or food category-specific cutoffs)