Serum 25(OH)D and Calcium Intake Predict Changes in Hip BMD and Structure in Young Active Men

Abstract

Peak bone mass (PBM) is mostly determined by genetics, but lifestyle and diet during youth may modify the final PBM. We examined changes in spine and hip bone mineral density (BMD) in a cohort of 146 males entering the US Military Academy (average age = 18.8 ± 1.1), randomly sampled from the full sample (755 males). Calcium intake was determined by a brief food frequency questionnaire. Serum 25(OH)D was measured by DiaSorin RIA, and intact (1–84) PTH was measured using the Elecsys (Abbott) on a single serum sample. BMD at the lumbar spine and total hip were measured at baseline and annually for 4 years by DXA (Lunar DPX-IQ). Hip structural analysis (HSA) was done using the methodology of Yoshikawa (JBMR 1994). Slopes of change in spine and hip BMD and HSA parameters were determined for each male. Average calcium intake was 1,803 mg/day (range 387–6,258). There was no significant use of calcium or vitamin D supplements. Men with calcium intake <800 mg lost 1 % of total hip BMD per year, whereas those with calcium intakes >800 mg a day gained 0.23 % BMD per year (p < 0.007), even after controlling for race and serum 25(OH)D. There was no relationship with change in spine BMD and calcium intake. Males with serum 25(OH)D level >20 ng/ml had a greater increase in hip BMD (0.2 % gain in hip BMD/year) as compared to a 0.3 % hip BMD loss per year in the 25(OH)D < 20 ng/ml group. Serum vitamin D was also correlated with hip cross-sectional area. Both relationships with 25(OH)D persisted after controlling for race and BMI (p < 0.03). However, there was no relationship between serum 25(OH)D and change in spine BMD. We conclude that in physically active college-aged men, dietary calcium intake and vitamin D status may modify peak bone mass acquisition.