Calcium absorption is significantly higher in adolescents during pregnancy than in the early postpartum period

• Published in: The American journal of clinical nutrition Vol. 78; no. 6; pp. 1188 - 1193
• Main Authors: O'Brien, K.O, Nathanson, M.S, Mancini, J, Witter, F.R
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01-12-2003; American Society for Clinical Nutrition, Inc
• Subjects: Absorptiometry, Photon; Adaptation, Physiological; Adolescent; Biological and medical sciences; bone density; Bone Density - drug effects; Bone Density - physiology; bone resorption; Calcium; Calcium - administration & dosage; Calcium - metabolism; Calcium - pharmacokinetics; Calcium Isotopes; dietary minerals; Female; Fundamental and applied biological sciences. Psychology; girls; hormones; human lactation; Humans; Intestinal Absorption; Lactation - metabolism; Lumbar Vertebrae - diagnostic imaging; Lumbar Vertebrae - metabolism; maternal nutrition; Mother. Fetoplacental unit. Mammary gland. Milk; nutrient balance; postpartum period; Postpartum Period - metabolism; Pregnancy; Pregnancy in Adolescence - metabolism; Pregnancy Trimester, Third - metabolism; Pregnancy. Parturition. Lactation; pregnant adolescents; Teenagers; Vertebrates: reproduction; Maryland; Human; stable isotopes; Calcium; Lactation; calcium absorption; Puerperium; Inorganic element; Osteoarticular system; Pregnancy; Absorption; Adolescent; Female; Bone; Adolescents; Isotopes
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/78.6.1188

Background: Early childbearing may limit skeletal consolidation and increase calcium demands in adolescents. Objective: The purpose of this study was to characterize calcium absorption in pregnant and lactating adolescents. Design: Fractional calcium absorption was evaluated in 23 adolescents (mean +/- SD age: 16.5 +/- 1.4 y) during the third trimester of pregnancy (34.7 +/- 1.0 wk gestation) and again in 15 of these adolescents 31 +/- 8 d after delivery. Eight adolescents were breast-feeding their infants during the follow-up study. Fractional calcium absorption was determined by using oral (46Ca or 44Ca) and intravenous (42Ca) stable calcium isotopes. Total-body and lumbar spine bone mineral density were measured in adolescents during the postpartum period by using dual-energy X-ray absorptiometry. Results: Fractional calcium absorption was significantly greater during pregnancy than at 3-4 wk postpartum [0.526 +/- 0.152 (n = 23) compared with 0.297 +/- 0.108 (n = 15); P < 0.0001]. Lumbar spine z scores measured 19-44 d after delivery (n = 15) were significantly associated with calcium intake during pregnancy (y = -3.53 + 0.107x; R2 = 0.355, P < 0.02) and were inversely related to fractional calcium absorption during pregnancy (y = 3.489 - 6.66x; R2 = 0.52, P = 0.002). A total of 33% (5/15) of adolescents had lumbar spine z scores that met the definition of osteopenia (n = 3) or osteoporosis (n = 2) in the early postpartum period. Conclusions: Calcium absorption in adolescents was significantly higher during the third trimester of pregnancy than in the early postpartum period, and higher calcium intakes during pregnancy appeared to be protective against loss of trabecular bone at the lumbar spine.