Evidence-based nutrition: Does it differ from evidence-based medicine?

Clearly defined processes exist for developing evidence-based guidelines in clinical medicine. Approaches such as the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) where recommendations are made on the basis of quality of evidence gathered in a systematic literature review are also appropriate for recommendations relating to nutritional management of disease. Strong recommendations are based on high-quality evidence derived from randomized controlled trials (RCTs). In nutritional studies, RCTs often examine risk factors and occasionally other surrogates of disease rather than clinical end-points. Criteria are suggested as to when such surrogates may be used. GRADE and similar approaches are less appropriate when considering recommendations regarding chronic disease prevention. Cancer develops over many years, and RCTs exploring nutritional measures to reduce risk are inappropriate. The World Cancer Research Fund (WCRF) has developed an approach in which recommendations are based on clearly defined 'convincing' or 'probable' relationships between nutritional variables and disease outcomes. The WCRF criteria have been adapted for developing a wide range of policy recommendations which provide opportunities for those responsible for implementing policy to select options best suited to their purpose. Recommendations related to nutrition policy tend to evolve as a delicate balance between political wisdom and judgement of the scientific evidence. However, policy recommendations are important since they have the potential to create environments which are conducive to the behavioural changes required for improved nutrition.