Addressing epidemiological and public health analytic challenges in outcome and impact research: a commentary on 'Prechewing Infant Food, Consumption of Sweets and Dairy and Not Breastfeeding are Associated with Increased Diarrhea Risk of Ten Month Old Infants'.

Based on a paper by Conkle et al 2016, in which the authors use a descriptive epidemiological design to examine the relationship of premastication and other dietary behavioral variables to childhood diarrhea in the US, we address larger issues of "plausible causality" and the challenges involved in moving from epidemiological studies to public health policy. Drawing on examples from breastfeeding research and water, sanitation and hygiene (WASH) research, we discuss the following propositions: 1. Effective outcome analyses require simultaneous investigation of different, even contradictory, pathways; 2. Outcome versus impact assessments require different analytic procedures including context analysis; 3. Impact analysis requires understanding the trade-offs between detrimental and beneficial outcomes in relation to potential interventions; 4. No estimates exist for the likely detrimental and beneficial impacts of banning premastication, much less for their trade-offs.