Appropriate days for measuring intake of dietary fat and cholesterol

Seven consecutive day food records were assessed in 224 free-living adult volunteers to (1) identify the smallest number of days, and which days of the week, would provide most of the information about dietary fat and cholesterol intake (assessed by B score) and (2) whether a complex mathematical formula for weighting certain days was required to achieve reasonable validity. A factor analytic approach was used to identify 3- and 4-day sets. The correlations with the 7-day average B score ranged from 0.95 for the best 4-day (Saturday through Tuesday) average B score to 0.91 for the best 3-day (Sunday through Tuesday) average B score. Simple averaging (no weighting) was found to be adequate to achieve this level of validity.