Types of Clinical Research Diets
Estimated Diet
Intake calculated: daily (after intake charted) using equivalency lists or tables of averages.
Measurement of diet: estimated in household measures.
Food source: varied.
Water source: varied.
Food preparation procedures: varied.
Food refusals: estimated.
Laboratory analysis of diet: no.
Advantages: closest to "free diet"; ease and speed of estimation; most accurate observational data.
Disadvantages: least reliable nutritive data; biased by change to hospital setting, different foods, etc.
Application: estimate of patient's preferred intake; data to supplement dietary history.
Weighed Diet
Intake calculated: daily (charted sometimes before and always after intake) using standard tables.
Measurement of diet: weighed (gram scale) portions (usual or calculated).
Food source: varied.
Water source: varied.
Food preparation procedures: varied or controlled.
Food refusals: weighed.
Laboratory analysis of diet: no.
Advantages: minimal inconvenience to patient; more reliable nutritive data.
Disadvantages: increased work with some increase in accuracy of data.
Application: more accurate idea of patient's preferred intake; more reliable observational data: general test diets.
Controlled Nutrient Diet
Intake calculated: daily (before and after serving to patient) using standard tables, special references or laboratory analyses.
Measurement of diet: weighed (torsion balance) controlled portions.
Food source: varied. Water source: controlled or varied.
Food preparation procedures: controlled or varied.
Food refusals: discouraged, weighed, calculated and perhaps replaced.
Laboratory analysis of diet: rarely.
Advantages: flexible, food variety; offers some variety and flexibility to patient.
Disadvantages: expensive (dietitian's time) unless computer available; constant monitoring for replacements.
Application: diets with focus on desired maximum or minimum quantity or quality of nutrients; investigative diets.
Constant Diet Intake calculated: before study using analyzed laboratory data, reliable manufacturers' data, USDA Handbook No. 8, or other tables and references.
Measurement of diet: weighed (torsion balance) controlled portions.
Food source: constant.
Water source: controlled constant or constant.
Food preparation procedures: constant. Food refusals: discouraged, replaced if possible; otherwise weighed, calculated and perhaps analyzed.
Laboratory analysis of diet: occasionally.
Advantages: highly accurate; dietitian's time used more efficiently; minimal calculations. Disadvantages: lack of variety and flexibility; requires a research kitchen, properly trained personnel, and standardized food preparation procedures; requires trial period for acceptability.
Application: diagnostic diets, research diets.
Metabolic Balanced
Diet Intake calculated: before study, using analyzed laboratory data, reliable manufacturers' data, USDA Handbook No. 8, or other tables and references.
Measurement of diet: weight (torsion balance) controlled portions.
Food source: constant.
Water source: constant.
Food preparation procedures: constant.
Food refusals: discouraged, replaced if possible; otherwise weighed, calculated and analyzed.
Laboratory analysis of diet: 2-3 times per menu.
Advantages: most reliable data; supported by actual laboratory analyses; dietitian's time used most efficiently; minimal calculations.
Disadvantages: requires analyses of all intake and excreta; only as accurate as collections and laboratory analyses; lack of variety and flexibility; requires research kitchen, properly trained personnel, and standardized food preparation procedures; requires trial period for acceptability.
Application: metabolic balance studies only.