title: A new statistical method for estimating the usual intake of episodically consumed foods with application to their distribution.
abstract: OBJECTIVE
  We propose a new statistical method that uses information from two 24-hour recalls to estimate usual intake of episodically consumed foods.
  
  
  METHODS
  The method developed at the National Cancer Institute (NCI) accommodates the large number of nonconsumption days that occur with foods by separating the probability of consumption from the consumption-day amount, using a two-part model. Covariates, such as sex, age, race, or information from a food frequency questionnaire, may supplement the information from two or more 24-hour recalls using correlated mixed model regression. The model allows for correlation between the probability of consuming a food on a single day and the consumption-day amount. Percentiles of the distribution of usual intake are computed from the estimated model parameters.
  
  
  RESULTS
  The Eating at America's Table Study data are used to illustrate the method to estimate the distribution of usual intake for whole grains and dark-green vegetables for men and women and the distribution of usual intakes of whole grains by educational level among men. A simulation study indicates that the NCI method leads to substantial improvement over existing methods for estimating the distribution of usual intake of foods.
  
  
  CONCLUSIONS
  The NCI method provides distinct advantages over previously proposed methods by accounting for the correlation between probability of consumption and amount consumed and by incorporating covariate information. Researchers interested in estimating the distribution of usual intakes of foods for a population or subpopulation are advised to work with a statistician and incorporate the NCI method in analyses.
authors.affiliation: jtooze@wfubmc.edu <jtooze@wfubmc.edu>
authors.forename: Janet A
authors.initials: JA
authors.lastname: Tooze
authors.forename: Douglas
authors.initials: D
authors.lastname: Midthune
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Dodd
authors.forename: Laurence S
authors.initials: LS
authors.lastname: Freedman
authors.forename: Susan M
authors.initials: SM
authors.lastname: Krebs-Smith
authors.forename: Amy F
authors.initials: AF
authors.lastname: Subar
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Guenther
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Carroll
authors.forename: Victor
authors.initials: V
authors.lastname: Kipnis
mesh_terms: D000704:Analysis of Variance; D004032:Diet; D004034:Diet Surveys; D002523:Edible Grain; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D015233:Models, Statistical; D015596:Nutrition Assessment; D012044:Regression Analysis; D012621:Seasons; D012737:Sex Factors; D016008:Statistical Distributions; D011795:Surveys and Questionnaires; D013997:Time Factors; D014675:Vegetables