Table 2.

Comparison of design features of dietary intervention and drug trials

	Dietary intervention trials	Drug trials
Patient population	Often children	Typically adults first and children studied only after efficacy established in adults
Inclusion and exclusion criteria	Often exclude underweight or malnourished; May exclude those whose usual diet is similar to intervention diet	Nutrition or usual diet rarely part of inclusion criteria
Common outcomes	Disease activity, quality of life, anthropometric parameters	Disease activity, quality of life
Concomitant medications	Determined by study question	May exclude certain medications to avoid excessive immunosuppression
Intervention	Supplementation or exclusion of a dietary component	Addition or withdrawal of a medication
Comparator	Placebo if studying supplement; usual or standard diet if studying dietary pattern	Placebo or effective therapy
Randomization	Essential	Essential
Blinding	Sometimes impossible	Essential
Dose finding	Uncommon	Based on phase 1 and 2 trials
Sample size	Based on minimally important difference	Based on minimally important difference
Adherence measurement	24 hour recalls, food frequency questionnaires, food checklists, and or measurement of biomarkers	Pill counts, electronic monitoring, direct observation therapy
Analytic approach	Intention to treat analysis, with or without additional per protocol analysis	Intention to treat analysis
Personnel	May include plant scientists, food scientists, registered dietitians, educational experts, behavior interventionists	May include experts in pharmacodynamics and pharmacokinetic measurements