Effect of making duplicate food collections on nutrient intakes calculated from diet records.

In a 1-yr study in which food intakes were recorded daily, subjects were asked to make duplicate food collections for 1 wk during each of the four seasons. Mean calculated energy intake of the 29 subjects was 12.9% less during the food collection periods than the mean for the entire year (which included collection periods). There were also significant reductions in the reported intake of all nutrients during the collection periods. Protein, vitamin A, saturated fat, and cholesterol intakes were decreased to the greatest extent. The actual decrease in energy intake was greater for the males than for the females, but the percentage was the same (12.9%). The younger group of subjects (less than or equal to 35) decreased energy intake 16.8% and the older group (greater than 35) 8.8%. Comparison of intakes during collection periods with intakes the week before and the week after showed that 28 of the 29 subjects decreased their energy intake from 1.1 to 32.3%. These data suggest that intakes of subjects during food collection periods do not represent their habitual levels of intake reported throughout the year.