Dietary calcium requirements do not differ between Mexican-American boys and girls

Abstract

Mexican Americans are an understudied ethnic group for determinants of bone health, although the risk of age-related osteoporosis is high in this rapidly growing sector of the U.S. population. Thus, the objective of the present study was to establish the dietary calcium requirements for bone health in Mexican-American adolescents by measuring calcium retention calculated from balance in response to a range of dietary calcium intakes and to determine predictors of skeletal calcium retention. Adolescents aged 12-15 y were studied twice on paired calcium intakes ranging from 600 to 2300 mg/d using randomized-order, crossover 3-wk balance studies. Skeletal calcium retention was calculated as dietary calcium intake minus calcium excreted in feces and urine over the last 2 wk of balance. A linear model was developed to explain the variation in calcium retention. Boys (n = 20) were taller and had higher lean mass, usual dietary calcium intake, bone mineral content, and serum alkaline phosphatase compared with girls, whereas girls (n = 20) had higher Tanner scores and greater fat mass. Calcium retention increased with calcium intake (P < 0.0001) and did not differ by sex (P = 0.66). In boys and girls considered together, calcium intake explained 33% of the variation in calcium retention. Serum alkaline phosphatase explained an additional 11% of the variation in calcium retention. Other variables measured, including the urine N-telopeptide of type I collagen/creatinine ratio, Tanner score, serum parathyroid hormone and 25-hydroxyvitamin D, weight, height, and body mass index, did not contribute to the variance in calcium retention. In adolescence, calcium retention in both Mexican-American boys and girls was higher than determined previously in adolescent nonHispanic white girls. This trial was registered at clinicaltrials.gov as NCT01277185.

Conflict of interest statement

Author disclosures: C. Palacios, B. R. Martin, G. P. McCabe, L. McCabe, M. Peacock, and C. M. Weaver, no conflicts of interest.

© 2014 American Society for Nutrition.

Figures

FIGURE 1

Study design, enrollment, and retention.

FIGURE 2

Urinary and fecal calcium excretion, calcium retention, and dietary calcium intake at the end of each 3-wk metabolic period under the low and high calcium intakes in Mexican-American boys and girls. The relation between urinary and fecal calcium excretion and dietary calcium intake (milligrams per day) (A). A sex × calcium intake interaction in urinary calcium was found (P-interaction < 0.05); the prediction equation for urinary calcium excretion in girls was 70.69 + 0.043 × calcium intake and in boys was 56.26 + 0.017 × calcium intake. For fecal calcium, there was no sex × calcium intake interaction or a sex effect (P-interaction > 0.05); calcium intake was significant (P < 0.0001), and the prediction equation for fecal calcium excretion is −122.4 + 0.69 × calcium intake. Calcium retention as a function of calcium intake (mean and 95% CI for regression lines) (B). There was no sex × calcium intake interaction or sex effect in calcium retention (P-interaction > 0.05). Calcium intake was significant (P < 0.0001), and the prediction equation for calcium retention was 60.3 + 0.282 × calcium intake (milligrams per day). The 95% CI for the sex difference was (−71, 147). Individual calcium retention on low and high calcium diets (milligrams per day) (C). Intraparticipant correlation was 0.76 (P < 0.0001).