Calcium metabolism in African American adolescent females

Rebecca Jane Bryant, Purdue University

Abstract

Osteoporosis, a condition of reduced bone mass resulting in increased skeletal fragility, affects 25–30 million Americans. African Americans have greater bone density and less incidence of osteoporosis than Caucasians or Asians. Approximately twenty-five percent of women of Anglo-Saxon origin over the age of fifty have osteoporosis. The prevalence of osteoporosis of the total hip is 16% among Hispanic women and only 10% among African American women (Looker et al., 1995). Within the female adult population there are more than 1.5 million bone fractures annually, resulting in healthcare costs in excess of $13 billion every year (Concensus Development Conference, 1993). It is important to understand racial differences in calcium handling throughout life. Twenty-one girls were recruited to participate in a three-week metabolic study which was conducted to measure calcium balance and calcium kinetics in 11–14 year old adolescent girls. A four day menu cycle consisted of typical teenage foods and averaged 1209 ± 2.5 mg/day of calcium. The girls ate and lived in a fraternity house on Purdue's campus to simulate a free-living environment. The adolescents showed a positive balance of 460 ± 236 mg/day, and excreted 37 ± 30 mg urinary calcium/day, and 661 ± 211 mg fecal calcium/day. Stable isotopic tracer techniques and compartmental modeling were used to determine calcium kinetics. Bone deposition was 1983 ± 603 mg/day, bone resorption was 1483 ± 533 mg/day, resulting in a net gain of 501 ± 222 mg/day calcium deposited in bone. Compared with Caucasian adolescent females, African Americans had significantly greater bone mineral density, balance, bone balance, bone deposition, bone resorption, and significantly less urinary and fecal excretion of calcium/day. Turnover of a compartment considered to be exchangeable calcium on bone was almost twice as fast in the African American, compared to the Caucasian girls, in marked contrast to biochemical bone turnover markers, which were lower. Biochemical markers of bone turnover underestimated bone turnover as determined by calcium kinetics in African American adolescent girls.

Degree

Ph.D.

Advisors

Weaver, Purdue University.

Subject Area

Nutrition|Cellular biology

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