Food patterns, flour fortification, and intakes of calcium and vitamin D: a longitudinal study of Danish adults

Abstract

Study objective: Deficiencies in calcium and vitamin D intakes are involved in the aetiology of osteoporosis, and health authorities recommend that the population consume a diet providing sufficient calcium and vitamin D. However, in 1987 the Danish Government withdrew a mandatory fortification of flour with calcium. This study examines intakes of calcium and vitamin D over time, in relation to food patterns, recommendations, and legislation.

Design: Food and nutrient intakes were measured by a short food frequency questionnaire (FFQ) and a thorough diet history interview, in 1987/88, and again six years later.

Setting: Copenhagen County, Denmark.

Participants: 329 men and women, aged 35-65 years at first examination in 1987/88.

Results: At both examinations the non-enriched median intakes of calcium in men as well as women were above the recommended 600 mg/day. However, apparently the fortification of flour supplied up to 30% of the total calcium intake, and without the mandatory fortification, the percentage of adults with intakes below this recommendation increased from 6% to 22%. This group of subjects consumed cheese, milk, and oatmeal less often than those who had calcium intakes over 600 mg/day. During the study period the median intakes of vitamin D, which were well below the recommended 5 micrograms/day, did not change significantly. Associations between foods and vitamin D intakes were, in general, weak and insignificant, except for a positive association with fish intake.

Conclusions: Data on calcium intakes suggest that the decision to stop the mandatory fortification of flour with calcium may have been premature. The short FFQ may be used for a rough classification of people in relation to their calcium intake, while this method seems insufficient for ranking vitamin D intakes.