Calcium-enriched bread supports skeletal growth of young rats

Abstract

Calcium (Ca) malabsorption is believed to aggravate negative calcium balance and contribute importantly to age-related bone loss. Although dairy products are considered a rich and bioavailable source of calcium, there are people who either avoid these products or do not consume them in adequate amounts. Therefore, there is a need for alternative food choices that can provide individuals with adequate calcium without a need for supplementation. The current study was undertaken to examine whether calcium bioavailability of a bread-based diet is comparable with that of a milk-based diet. Additionally, the calcium bioavailability of these two diets were compared with semi-purified diets with varying amounts of fat and protein. Forty, 28 day old, male Sprague-Dawley rats were divided into four treatment groups and fed for 8 weeks. Treatments were as follows: control, received a semi-synthetic diet; bread, received a bread-based diet in which bread provided 100% of the CHO, 79% of the protein and 16% of the fat; milk, received a diet composed of 49.4% ( w w ) non-fat dried milk; and HFHP, received a semi-synthetic diet with higher fat and protein contents than all the other groups. All the diets, except HFHP, were formulated to be iso-caloric and isonitrogenous. Absorption of Ca was assessed 8 days before the end of the study for a five-day period using the balance technique. Calcium absorption was significantly lower in the milk and HFHP groups in comparison to the bread and control groups. However, skeletal growth was not jeopardized in any of the treatment groups as judged by femoral density and mineral content and tibial protein content. Despite similar energy intakes, the final mean body weight of animals fed the milk-based diet was significantly lower than the other groups. These results indicate that enriched bread can serve as a good source of bioavailable calcium. Additionally, our data suggest that diets with higher fat content may interfere with calcium absorption.