NU_nutrition_TS

This is a contentious issue which is often brought up to cast doubt on any study where a food frequency questionnaire or 24 hour dietary recall is used. I happened across this study, which casts some light on this phenomenon.

The methodology was as follows:

Quote

The purpose of the study was to assess dietary measurement error using two self-reported dietary instruments—the food frequency questionnaire (FFQ) and the 24-hour dietary recall (24HR)—and unbiased biomarkers of energy and protein intakes: doubly labelled water and urinary nitrogen.

Of the 484 men and women (age range 40-69 years) who participated, it was found that 9% of men and 7% of women were 'under-reporters' for dietary protein and total energy intakes on 24-hour recalls and for food frequency questionnaires, the figures were 35% and 23% respectively. When it came to total energy intakes men were inclined to under-report by 12-14% on 24-hour recall and by 31-36% on food frequency questionnaires. For women the figures were 16-20% and 34-38% respectively.

So it seems if you want to use a study that is less prone to the under-reporting phenomenon then pick one that uses 24-hour recall rather than food frequency questionnaires and one that uses men as subjects rather than women. Why? Because the technique of doubly labelled water most often used to determine total energy expenditure in studies have, themselves, an average 10% margin of error for accuracy and, depending on the lab that performs the tests and the formula used to calculate expenditures, they can be considerably more variable than that!