Evidence-based nutrition — using a meta-analysis to review the literature

Abstract

A meta-analysis is the structured result of a literature review in which results from several independent but related or comparable studies are systematically and statistically combined or integrated in order to increase power and precision. In this paper the advantages and limitations of a meta-analysis and the different steps (process) to conduct one are briefly outlined. These steps include formulation of the objectives of the meta-analysis (the research questions); selection of appropriate studies (literature search); defining and applying inclusion and exclusion criteria for studies; coding (stratifying, scoring) of studies combined with a qualitative assessment; and quantitative assessment and statistical analysis. In the analysis the heterogeneity of studies is tested, study results are pooled, combined level of effect calculated, and interactive effects and effects of confounders and moderators determined. This is followed by interpretation of the combined results, drawing of conclusions and writing of the review. The meta-analysis method can be used by nutrition researchers and practitioners to structurally evaluate and integrate large amounts of often conflicting information. When possible limitations and problems are recognised and handled, a meta-analysis can be used to minimise bias in results, to formulate new hypotheses, to motivate and direct further research and to form a firm, evidence-based platform for nutrition policy.