Dietary diversity is differentially associated with diet quality across food groups

Dietary diversity is considered an essential characteristic of diet quality, including nutrient adequacy and chronic disease risk. However, in high-income countries, its relationship with diet quality remains complex and may vary depending on the food group in which diversity is present. This study aimed to explore how within-food-group diversity is associated with diet quality in Western diets.

We used data of adults from the latest French national dietary survey (2014-2015), with dietary intake assessed using three 24-h recalls. Foods were categorized into 19 food groups and 114 subgroups, based on FoodEx2, and mean daily food and nutrient intakes were computed. Dietary diversity-overall and within food groups-was assessed along three dimensions: count, evenness, and nutrient dissimilarity of subgroups consumed. Diet quality was evaluated using three indicators: nutrient adequacy, nutrient security, and risk of chronic disease. Multivariable linear models were used to examine associations between diversity and diet quality, adjusting for energy intake and the quantity consumed in each food group to distinguish the specific associations of diversity.

The associations of within-food-group diversity with diet quality varied considerably by food groups, diversity dimension and diet quality indicator. In most cases, within a single food group, associations were either mixed or null. Moreover, quantity consumed often showed a stronger association with diet quality than diversity.

The associations of within-food group diversity with diet quality vary among food groups and according to the dimension of the diversity. Therefore, our results support the view that diversity should be promoted in specific food groups and along specific dimensions rather than in general and in isolation from the quantity.