Submitted to: International Dairy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2005
Publication Date: 2/16/2007
Citation: Gutierrez, A.M., Farrell, H.M., Attaie, R., Mcwhinney, V.J., Wang, C. 2007. Effects of bovine and caprine monterey jack cheeses fortified with milk calcium on bone mineralization in rats. International Dairy Journal. 17:255-267.
Interpretive Summary: Americans are consuming more cheese each year, and these and other dairy products are becoming important sources of calcium in the diet. The major proteins of milk, called caseins, carry calcium in small packages called micelles. Experiments on the comparison of goat’s and cow’s milk caseins showed that one genetic type of goat’s milk casein, regardless of breed, is much better at carrying calcium than that of other goat’s or cow’s milk. Cheeses with extra calcium were then made from the high calcium carrying goat milk and normal cows’ milk. Feeding studies showed that the high calcium carrying goat cheese doubled calcium blood levels in normal rats and also resulted in better bone strength as well. So these genetically different goats produce caseins that can carry extra calcium and then cheese made from this milk produces stronger bones in the rats. This shows that manipulation of the casein types in milk can lead to stronger bones in animals. Extension of this information to human studies will aid cheese manufacturers who are attempting to enhance the nutritional quality of their products. These studies could also lead to the improved nutritional value for milk proteins in all dairy products and possibly as ingredients in other foods.
Technical Abstract: Bovine and caprine Monterey Jack cheeses were produced unfortified (cheese) or fortified with milk calcium (Ca) cheese. Five groups of male rats were fed a control diet or more of four experimental diets: bovine cheese diet, bovine Ca-cheese diet, caprine cheese diet, and caprine Ca-cheese diet to test their effects on calcium and magnesium absorption as well as bone mineralization, in the latter case, total bone mineral content (BMC), density (BMD) and femoral breaking force were assessed. Significant differences (P>0.05) were found for calcium absorption and digestibility with the data yielding the pattern: caprine Ca-cheese> caprine cheese = bovine Ca-cheese> bovine cheese> control. Significant increases (P<0.05) occurred in BMC, BMD and breaking force in the femoral bone with the pattern: caprine Ca-cheese > caprine cheese> bovine Ca-cheese > bovine cheese> control; this pattern of deposition was close to that of calcium absorption. BMC, BMD and breaking force in the femoral bone for caprine Ca-cheese and caprine-cheese diet groups were significantly higher than those of bovine Ca-cheese and bovine cheese diet groups (P<0.05), perhaps due to the protein and lipid compositional differences between caprine and bovine milks. Our findings suggest that caprine cheese unfortified or fortified with milk calcium had the most positive effects on calcium absorption and bone mineralization in rats with bovine cheeses still significantly greater than the non casein control.