Creation of a Database for the Calculation of Nutrient Intake Over Time

In 1987–1988, the first Dutch National Food Consumption Survey (DNFCS) was carried out; similar surveys were conducted in 1992 and 1997–1998. In each survey, food consumption data were converted into energy and nutrients using the most up-to-date version of the Dutch food composition table. To enable valid comparisons of nutrient intake over time specific food composition tables (Trend Table-1 (TT-1) for DNFCS-1 and TT-2 for DNFCS-2) were created. In these tables, for 20 nutrients, the composition of 550 selected food items was compared and reasons for differences were investigated. The food composition table used for DNFCS-3 (last update in 1997) was the reference table. To avoid artificial changes, differences as a consequence of improvements of the database were corrected in retrospect; real changes in the food composition remained intact. In TT-1 nearly 3500 modifications were made. Most of them concerned the composition of macronutrients. About 40% of the corrections arose from more and better analytical data; 6% were missing values. In both TTs many changes were related to the fatty acid composition of foods and were a consequence of changing the expression of saturated, monounsaturated and polyunsaturated fat into fatty acids. In TT-2 more than 2800 modifications were made; besides changes in the fatty acid composition, about 20% reflected improvements in the quality of data, and 16% were missing values. Changes in the different food groups and consequences of the modifications are discussed in more detail.