In Cochrane nutrition reviews assessment of dietary adherence varied considerably.

OBJECTIVES: Our aim was to investigate if and how Cochrane nutrition reviews assess dietary adherence to a specific dietary regimen. STUDY DESIGN AND SETTING: Cochrane nutrition reviews fulfilling the following criteria were included: systematic review of randomized controlled trials including adults and investigating the effect of caloric restriction, dietary pattern, foods, nutrients, supplements, or other nutrition-related-interventions. Extensive data extraction and descriptive statistics were conducted. RESULTS: Overall, 226 Cochrane reviews were included. Most reviews mentioned dietary adherence in the main text (n = 174), predominantly in the Methods and Results. Dietary adherence was assessed in 76 reviews and defined in 19. It was included in the risk of bias (RoB) assessment in 20 reviews with nine using a newly created RoB domain for dietary adherence, and considered as outcome in 37 reviews. Seventy-five reviews addressed degree of adherence and five treatment effects considering the degree of adherence. CONCLUSION: Dietary adherence was reported in a heterogeneous manner in Cochrane nutrition reviews. Due to its high importance, we suggest that systematic reviews report the assessment and degree of dietary adherence measured in primary studies. Dietary adherence can further be examined as outcome, evaluated within the RoB (deviations from intended interventions) and included in sensitivity analyses.