Individualized high dairy protein + walking program supports bone health in pregnancy: a randomized controlled trial

BACKGROUND: Pregnancy induces bone mineral mobilization, which may be further compromised if diet and physical activity are suboptimal. OBJECTIVES: We aimed to determine the effects of a Nutrition + Exercise intervention during pregnancy on maternal calciotropic and bone biomarker profiles throughout pregnancy and the postpartum. METHODS: In the Be Healthy in Pregnancy (BHIP) randomized controlled trial, 203 of 225 participants who consented to the bone health substudy were, randomly assigned at 12-17 weeks gestation to receive either usual care (control) or a structured and monitored Nutrition + Exercise plan (intervention) providing an individualized high dairy protein diet and a walking program throughout pregnancy. Maternal serum total procollagen type 1 N-terminal propeptide (P1NP; bone formation), C-terminal telopeptide of type I collagen (CTX; bone resorption), and insulin-like growth factor-1 (IGF-1) were measured by ELISA, and vitamin D metabolites by ultra-performance LC tandem MS at early and late pregnancy, 6 mo postpartum, and in cord blood. RESULTS: In 187 participants completing all measures, significantly higher intakes were observed in the intervention than in the control group for total protein (P < 0.0001), protein intake from dairy foods (P < 0.0001), and calcium (P < 0.0001), whereas vitamin D intake was similar between treatment groups in both the second and third trimesters. The intervention group had significantly lower serum CTX at end of pregnancy (mean ± SD: 0.78 ± 0.31 ng/mL; n = 91 compared with 0.89 ± 0.33 ng/mL; n = 96, P = 0.034) and in cord serum (0.58 ± 0.13 ng/mL; n = 31 compared with 0.69 ± 0.18 ng/mL; n = 22, P < 0.025). Serum concentrations of P1NP rose significantly (P < 0.02) from early pregnancy to 6 mo postpartum for the intervention group only. Serum 25-hydroxyvitamin D status was >50 nmol/L for 97% of all participants. CONCLUSIONS: Higher maternal dietary protein and calcium intakes than usual care in concert with normal vitamin D status minimized bone resorption and maintained bone formation and may protect bone health during pregnancy.This trial was registered at clinicaltrials.gov as NCT01689961.