Dietary calcium: Effect of bioavailability and level of intake on bone growth, development and maintenance in the rat
Peterson, Catherine Ann
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https://hdl.handle.net/2142/23653
Description
Title
Dietary calcium: Effect of bioavailability and level of intake on bone growth, development and maintenance in the rat
Author(s)
Peterson, Catherine Ann
Issue Date
1994
Doctoral Committee Chair(s)
Erdman, John W.
Department of Study
Health Sciences, Nutrition
Discipline
Health Sciences, Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Nutrition
Language
eng
Abstract
Experiments were conducted to determine the effect of calcium intake on bone growth, development and maintenance using the rat as a model. The central hypotheses that were tested were: (I) dietary calcium provided from a low bioavailable source will compromise both bone quality and bone quantity in the young and old animal; and, (II) the higher the total level of dietary calcium during the critical phase of peak bone mass acquisition, the greater the amount of peak bone mass attained, irrespective of the calcium intake after this critical phase. The first hypothesis was addressed by evaluating the effects of varied calcium bioavailability on bone development (young animal) and bone maintenance (aged animal) by the application of bone composition and histologic/histomorphometric techniques. The results of these studies demonstrated that the young animal responds to a low bioavailable calcium source (spinach) by reducing the mineralization of bone matrix and stimulating bone resorption, with a consequent impairment in bone growth and development. In contrast, despite the stable structure of the mature bone, a low bioavailable calcium source may also compromise the skeletal integrity of the aged animal but this compromise is brought about by an increase in bone resorption only. The second hypothesis was addressed by comparing the effect of a calcium deficit or surfeit on bone growth and development in the early phase of peak bone mass attainment with the late phase of peak bone mass attainment using the female Sprague-Dawley rat as a model. Results of this experiment indicate that increasing the calcium intake after adolescence (12 weeks old) of those female rats consuming a low calcium diet will not substantially alter the adult bone volume of the metaphyseal region of the proximal tibia. Further, low calcium intakes through adolescence retard and prolong longitudinal bone growth. In contrast, however, those rats fed a diet providing calcium either at (0.5%) or twice the NRC requirement level through adolescence had greater tibial bone volume as an adult when fed diets containing 1.0% calcium after this time period. It appears that the mechanism for this increase involves both a protection from resorption and an increase in bone formation/mineralization. In sum, the data obtained from these experiments positively confirmed both of the above stated hypotheses. Human implications include the identification of the importance of the bioavailability of dietary calcium in both the prevention (young) and treatment (aged) of osteopenia; and that high calcium intakes from birth through and including young adulthood are important in achieving genetically-programmed peak bone mass.
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