Design and quality control issues related to dietary assessment, randomized clinical trials and meta-analysis of field-based studies in developing countries.
The essential design and quality control aspects of dietary assessment, randomized controlled trials (RCT) in developing countries and their subsequent meta-analysis are reviewed. Dietary assessment protocols consist of three stages: measurement of food intakes using a method appropriate for the study objectives, calculation of nutrient intakes and finally an evaluation of their nutrient adequacy. The latter may involve: 1) assessment of dietary diversity (average number of different foods consumed per day) and selected indices of dietary quality such as intakes of animal source foods (g/d); 2) percentage of energy from protein, fat and animal protein; 3) selected nutrient densities; and 4) dietary phytate:zinc molar ratio, as well as the prevalence of inadequate nutrient intakes calculated using a probability approach. To establish causality between the nutrient inadequacies identified and adverse health outcomes, RCT must be undertaken. A prerequisite of RCT is double-blind randomization, a procedure designed to eliminate biases arising from baseline confounding variables, unintended interventions and ascertainment bias. Results from existing RCT can be summarized via meta-analysis to gain a better understanding of the population relationship. Meta-analysis is a statistical technique involving linear models or generalized linear models, which can be performed after locating the individual studies, and selecting and abstracting all the necessary data.
Department of Human Nutrition, University of Otago, Dunedin, New Zealand. Rosalind.Gibson@stonebow.otago.ac.nz
Rosalind S
RS
Gibson
Sunil
S
Sazawal
Janet M
JM
Peerson
D003906:Developing Countries; D004032:Diet / Q000592:standards; D004311:Double-Blind Method; D006801:Humans; D015201:Meta-Analysis as Topic; D015596:Nutrition Assessment; D011786:Quality Control; D016032:Randomized Controlled Trials as Topic; D012107:Research Design