DO WE NEED INFORMATION ABOUT PORTION SIZES TO RANK INDIVIDUALS BY THEIR NUTRIENT INTAKES

Nutrient intakes calculated from 7-day weighed intake records for a co mmunity sample of 99 men and women were compared with those estimated from the same records, but with mean portion weights substituted for t he actual weights. For many nutrients, approximately half of the mean portion records yielded intakes within 10% of the weighed record value s. Correlation coefficients between the two estimates of intakes were high (0.64-0.97). Between 58 and 74 subjects were classified in the sa me third of the nutrient distributions and only between zero and four classified in opposite thirds. Using estimated portion weights is like ly to reduce the degree of misclassification only slightly. It is ther efore concluded that for most nutrients a diary with standard portion weights may be as likely to detect diet-disease relationships in popul ation studies as a diary with estimated weights and only slightly less likely to detect such associations than a weighed intake survey.