Validity of a food frequency questionnaire and a food diary in a short-term recall situation.

The purpose of this study was to compare intakes of eight nutrients computed from a food frequency questionnaire (FFQ) and from 3-day food diaries with known values. Total food intake of 19 healthy adult volunteers (10 men and 9 women) was monitored for 2 weeks. Each week, subjects completed a 3-day diary and a 1-week FFQ. Subjects had previously completed one diary and one FFQ with respect to their usual diets. FFQs and diaries were analyzed for calories, protein, fat, cholesterol, calcium, iron, vitamin A, and vitamin C. All nutrients were underestimated by the FFQ (all p less than .05). Subjects omitted foods from the FFQ and incorrectly reported consumption frequencies. Vitamin A (p less than .001) and calories (p less than .05) were underestimated by the food diary. It is concluded that factors such as frequency of eating, pairing of foods, and explicitness of FFQ items affect recall accuracy. Those factors could influence the choice of FFQ design and administration.