While studies have evaluated the reproducibility and validity of dietary patterns in various adult populations, 6, 7, 19 - 21 the validity of a semi-quantitative food frequency questionnaire (SFFQ) to derive dietary patterns in the Mexican population has not been evaluated. For those reasons, it is useful to evaluate the validity of the food frequency questionnaire (FFQ) for assessing identification of dietary patterns in a particular study population. 18 Furthermore, dietary patterns may vary across populations with respect to food availability, socioeconomic status, resident area, ethnic group, and culture. 10, 17Īssessment of dietary patterns by factor analysis involves subjective judgment in classification of food items, determination of the number of factors to retain, method of rotation, and labeling of dietary patterns.
Factors can be rotated (usually orthogonally) to enhance interpretability, and factor scores are computed for each individual. 3, 9, 15, 16 Factor analysis, a data reduction method which creates linear combinations of foods or food groups to identify the principal factors behind the largest variation in food consumption, is one of the most commonly used of these a posteriori techniques. 11, 12ĭietary patterns can be assessed with different statistical techniques: a priori techniques using score-based approaches, like the Mediterranean diet score or healthy eating index, 13, 14 or a posteriori methods implemented with data-driven techniques such as factor analysis, cluster analysis, or, more recently, reduced rank regression. 7, 8 Thus, dietary pattern analysis has been proposed to account for the cumulative and complex effects of simultaneous consumption of multiple nutrients or foods on a daily basis, 4, 9, 10 and to understand the role whole diets play in disease occurrence. 4 Finally, single nutrient assessment may be confounded by the effect of dietary patterns, with which consumption of specific nutrients is normally associated. 3, 5, 6 Further, intercorrelation between some nutrients makes it complicated to evaluate their effects independently. It fails to account for interactions among nutrients 3, 4 and cannot explain the synergistic effects of recognized or unrecognized constituents of daily food consumption. 3 However, that approach has some important limitations.
Nutritional epidemiology research has traditionally adopted a reductionist approach 1, 2 focusing on relationships between individual nutrients or foods and disease.
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