The association between dairy and bone quality in Puerto Rican adults varies by dairy food and fat content

Dairy foods have been shown to improve BMD, a measure of bone quantity, yet there is little understanding of their influence on measures of bone quality. The aim of this study was to examine associations of dairy intakes with two measures of bone quality: bone material strength index (BMSi) and spinal trabecular bone score (TBS), and the potential mediating role of inflammation, among adults from the Boston Puerto Rican Osteoporosis Study. This cross-sectional analysis included dietary intake assessed with a culturally tailored food frequency questionnaire. Dairy food groups were calculated as total dairy (milk, yogurt, and cheese), milk, cheese, yogurt, desserts, non-fat, and fat-containing dairy. Bone material strength index (n = 138) was measured using micro indentation with the Osteoprobe, and TBS (n = 412) was calculated from DXA scans. Multivariable linear regression estimated the association of dairy food intakes with each bone measure. Mediation analysis evaluated direct and indirect (via inflammatory cytokines) associations between dairy intake and BMSi and TBS. Participants were 77.4% female with mean age 70.5 ± 6.9 yr. Higher intakes of total dairy (β = 1.79, p = .04) and milk (β = 1.74, p = .06) were associated with BMSi. Higher intake of fat-containing dairy (β = .018, p = .04) was positively associated with TBS, while higher intake of non-fat dairy (β = -.042, p = .02) was inversely associated with TBS. Inflammatory cytokines were not identified as mediators of these associations. Dairy food intakes were associated with measures of bone quality; however, the foods that predicted BMSi and TBS differed. Bone material strength index was influenced by total dairy and milk, while TBS was influenced by dairy fat content. Future studies should examine the impact of dairy matrix components on immune and inflammatory pathways.