Analysis of patterns of food intake in nutritional epidemiology: food classification in principal components analysis and the subsequent impact on estimates for endometrial cancer

Public Health Nutr. 2001 Oct;4(5):989-97. doi: 10.1079/phn2001168.


Objective: To assess the effect of different methods of classifying food use on principal components analysis (PCA)-derived dietary patterns, and the subsequent impact on estimation of cancer risk associated with the different patterns.

Methods: Dietary data were obtained from 232 endometrial cancer cases and 639 controls (Western New York Diet Study) using a 190-item semi-quantitative food-frequency questionnaire. Dietary patterns were generated using PCA and three methods of classifying food use: 168 single foods and beverages; 56 detailed food groups, foods and beverages; and 36 less-detailed groups and single food items.

Results: Classification method affected neither the number nor character of the patterns identified. However, total variance explained in food use increased as the detail included in the PCA decreased (approximately 8%, 168 items to approximately 17%, 36 items). Conversely, reduced detail in PCA tended to attenuate the odds ratio (OR) associated with the healthy patterns (OR 0.55, 95% confidence interval (CI) 0.35-0.84 and OR 0.77, 95% CI 0.49-1.20, 168 and 36 items, respectively) but not the high-fat patterns (OR 0.95, 95% CI 0.57-1.58 and OR 0.85, 0.51-1.40, 168 and 36 items, respectively).

Conclusions: Greater detail in food-use information may be desirable in determination of dietary patterns for more precise estimates of disease risk.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Case-Control Studies
  • Dietary Fats / administration & dosage*
  • Endometrial Neoplasms / epidemiology
  • Endometrial Neoplasms / etiology*
  • Energy Intake
  • Feeding Behavior*
  • Female
  • Food / classification*
  • Humans
  • Middle Aged
  • New York / epidemiology
  • Odds Ratio
  • Principal Component Analysis
  • Risk Factors
  • Surveys and Questionnaires / standards*


  • Dietary Fats