Unique Considerations Regarding Systematic Reviews in the Field of Nutrition

The use of systematic reviews in the field of nutrition has proliferated in recent decades, playing an important role in formulating dietary guidance, establishing nutrient reference intake values, evaluating applications for food and supplement label health claims, and identifying research needs. By affording the opportunity to conduct unbiased meta-analyses, well-conducted systematic reviews allow for combination of data from multiple small studies to increase statistical power. This is particularly valuable when generating dose-response curves. Discussed are unique considerations associated with conducting nutrition-related systematic reviews. These may include baseline nutrient exposure and status of study participants prior to initiating the intervention, bioequivalence and bioavailability of different nutrient chemical forms, nutrient/nutrient interactions, nutrient/drug interactions and nutrient/food interactions, bioavailability of nutrient storage reservoirs, multiple and interrelated nutrient biological functions, undefined nature of nutrient intervention (generally food-based studies), and compensatory dietary changes triggered by an intervention. A fundamental value of systematic reviews lies in the transparent methodological approach used for conduct and documentation, facilitating reproducibility and efficient updating. A fundamental limitation is the narrow scope of the questions addressed and intensive resources necessary to complete comprehensive, unbiased reviews. Of note, systematic reviews provide an opportunity to identify evidence gaps and identify recommendations for future research.