Applications and advances of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology in nutrition and child health

The relationship between human health and nutrition is complex and limited widely accepted guidance on proper methods of evidence synthesis is available for nutritional issues. While concepts and methods of evidence synthesis in pharmacological treatments can be mostly applied to nutritional interventions, characteristics unique to the nutrition- and dietetics-related topics can lead to distinct challenges that may not be encountered in evidence synthesis of traditional medical interventions. In addition to traditional methods for pooling the results, state-of-the-art methodologies such as GRADE or network meta-analysis, while being widely used in many medical fields, their use in the field of nutrition and food science is surprisingly rare. This thesis begins with the assessment of methodological quality of available public health guidelines on sugar intake to determine the extent to which nutritional guidelines follow currently available guidance in evidence synthesis and making practice recommendations. Subsequently, we present two examples of proper implementation of evidence synthesis methods in standard pairwise meta-analysis and indirect treatment comparison and handling of relevant challenges including applications of GRADE approach. Further, this thesis presents a network meta-analysis in the field of nutrition and child health in which the challenges of conducting multiple treatment comparison are tackled and a new approach for presenting and making conclusion from network meta-analysis results is proposed.