A priori vs a posteriori: Which approach identifies the most sustainable foods?

The use of multiple methods helps capture the complexity of food choices in the context of sustainability, providing insights for the development of sustainable dietary guidelines that balance health-related nutritional, environmental, and economic factors, suggests a study.

A total of 2,553 Portuguese adults who completed two non-consecutive 24-h recalls during the most recent National Food, Nutrition and Physical Activity Survey of 2015‒2016 provided data for analysis.

The authors selected culturally acceptable food items for analysis based on consumption frequency and quantity. They also evaluated these items for health-related nutritional attributes (NOVA-classification and Nutrient-Rich Food Index 9.3), environmental impact (greenhouse-gas emissions and land use from the SHARP-Indicators Database), and cost (retail prices).

The a priori approach employed a sustainability score, while the a posteriori approach used cluster analysis.

Overall, 366 food items were deemed culturally acceptable, covering 75 percent of total daily energy intake. Both strategies identified sustainable foods as those combining high nutrient-density and low processing levels with low environmental impact and cost.

Ninety-six items were identified as sustainable using the a priori approach, while 144 items were selected using the a posteriori analysis, exhibiting variations in food categories.

Both methods identified a significant number of unprocessed and minimally processed foods, but the a posteriori approach yielded a higher proportion. Furthermore, “[n]utrient richness, environmental impact, and cost were significantly better for the most sustainable foods in both approaches,” according to the authors.