Higher Dairy Intakes Are Associated with Higher Bone Mineral Density among Adults with Sufficient Vitamin D Status: Results from the Boston Puerto Rican Osteoporosis Study

Abstract

Dairy foods have been shown to improve bone mineral density (BMD) in non-Hispanic whites. Puerto Rican adults have a higher prevalence of osteoporosis and vitamin D deficiency than non-Hispanic whites. However, there is little understanding of lifestyle influences on bone in this population. The aim of this study was to examine associations of dairy intakes with BMD among adults from the Boston Puerto Rican Osteoporosis Study with and without adequate serum vitamin D status. A total of 904 participants in this cross-sectional analysis provided dietary intakes with a culturally tailored food-frequency questionnaire. Dairy food groups were calculated [total dairy, modified dairy (without cream or dairy desserts), fluid dairy (milk+yogurt), cheese, yogurt, and cream and desserts]. BMD (grams per centimeter squared) was measured using dual-energy X-ray absorptiometry. Vitamin D status was defined as sufficient (serum 25-hydroxyvitamin D [25(OH)D]≥20 ng/mL) or insufficient (<20 ng/mL). General linear models were used to examine associations between dairy intake and BMD, stratified by vitamin D status. Of the total sample, 73% were women, of whom 87% were postmenopausal. Mean ± SD age was 60.0±7.6 y and mean ± SD body mass index (kg/m2) was 32.3±6.6. Mean serum 25(OH)D (range: 4-48 ng/mL) was 14.3±3.6 ng/mL in insufficient individuals and 26.0±5.5 ng/mL in sufficient individuals. In the full sample, higher intakes of modified dairy foods (β=0.0015, P=0.02) and milk (β=0.0018, P=0.04) were associated with higher femoral neck (FN) BMD. Among those who were vitamin D sufficient, higher intakes of total dairy (P=0.03-0.07), fluid dairy (P=0.01-0.05), and milk (P=0.02-0.09) were significantly related to higher FN and lumbar spine BMD, respectively. Among vitamin D-insufficient participants, dairy intakes were not associated with BMD (P-range = 0.11-0.94). Dairy food intakes were associated with higher BMD among adults, particularly those with sufficient vitamin D status. Future studies should confirm findings longitudinally and assess culturally acceptable lifestyle interventions to improve bone health among Hispanic adults. This trial was registered at clinicaltrials.gov as NCT01231958.