Developing the Evidence Base for Nutrition Recommendations

By Ann Liu, PhD

Systematic reviews are the basis for nutrition policy and guidance, but gaps in the evidence base can impact recommendations. Presenters at the symposium “Creating the Future of Evidence-Based Nutrition Recommendations, Using Lipid Research Case Studies” sponsored by ILSI North America spoke on various aspects that inform the process of developing dietary guidance and its implementation on Saturday, March 28. Major policy and regulatory groups such as the Dietary Guidelines for Americans Scientific Advisory Committee, American Heart Association, and the Institute of Medicine use systematic reviews as the basis for their decision making, but often the ability to make recommendations can be hampered by a lack of strong evidence.

The process of developing evidence-based reviews, such as the one used by the USDA Nutrition Evidence Library, must be rigorous, transparent, and minimize bias, because these reviews inform federal nutrition policy and programs. At the outset, key systematic review questions are developed which should reflect important decisional dilemmas in public health nutrition guidance.

The next critical step is deciding on inclusion and exclusion criteria, which determines what literature is included in the evidence base. Criteria that may be considered include study design, study duration, size of groups, drop out rates, and the health status of participants. This process is thoroughly documented and transparent so it can easily be determined why a study was included or excluded. The evidence base will go on to be evaluated by expert panels in order to make recommendations and guidances.

How can scientists ensure that their research is included in the evidence base?

– When designing studies, it is important to consider the validity of the study design, the impact of endpoints, and the relevance and feasibility of interventions. Are the outcomes meaningful and are they translatable? If not, what additional information do you need? Researchers can also use the gaps in the literature identified in Nutrition Evidence Library systematic reviews to inform future investigations.
– If studying chronic disease risk, use validated surrogate biomarkers.
– Carefully consider your comparator group. One of the most common reasons studies are discounted from systematic reviews is they did not include appropriate control groups.
– Once you are ready to report your results, follow established reporting standards such as the Consolidated Standards of Reporting Trials (CONSORT) for randomized clinical trials or the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. This can help ensure that key information is included and is available for data abstraction in future systematic reviews and meta-analyses.
– Participate in the process. Once draft reports such as the Dietary Guidelines for Americans Scientific Report are issued, there is the opportunity for public comment. Feedback from scientists with expertise is strongly encouraged.

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