Food habits in Swedish adolescents. Meal pattern, food choice and bioavailability of iron 1994 and 2000

Abstract

The general iron fortification of white wheat flour was removed after 50 years of iron fortification. It was considered important to evaluate the effects of withdrawal of iron fortification among vulnerable groups in the population. Adolescents have high iron requirements for growth and the girls for menstrual losses. To study the effects of the removed iron fortification, two cross-sectional studies were performed on representative samples of adolescents, 15-16 years old, in Göteborg, Sweden, before and after the iron fortification had been removed, 1994 and 2000. Studies on validity, using doubly labelled water, and relative validity showed that the dietary assessment method, diet history interview, was valid as a reference method for this age group. Many of the boys and girls consumed three main meals daily and often two of these were prepared meals. However, there was a shift towards more irregular breakfast consumption and among the boys less frequent school lunch consumption in 2000 compared to 1994. Concerning dinner, there was an increase in subjects with daily consumption in 2000. Omitting breakfast was an important indicator of less healthy lifestyle and a food choice leading to a poorer nutrient intake. Omitting both breakfast and lunch was an even stronger indicator of a lifestyle that may also have effects on future health. In 1994, fortification iron from white wheat flour represented 40% of the dietary iron intake. The marked decrease in total iron led to a lower amount of available iron. Predictions of iron absorbed, taking enhancing and inhibiting factors at meal level into account, indicated that absorbed iron was low, compared to the median requirements, especially among girls, both in 1994 and 2000. For girls predicted iron absorption was lower in 2000 compared to 1994. The decreased intake of fortification iron, lower meat, and thus heme iron intake, was not counteracted by increased fish and decreased milk intake. The girls, with largest iron requirements had food habits giving lower iron absorption and this vulnerable group is of concern. For boys there was higher calculated iron absorbed in 2000 compared to 1994. More meat, heme iron and vitamin C and less milk favoured bioavailability of iron. The results show that increase in iron absorption can be achieved with dietary modification.