Dairy Intake Is Protective against Bone Loss in Older Vitamin D Supplement Users: The Framingham Study

Abstract

BackgroundPrevious studies showed beneficial effects of specific dairy foods on bone health in middle-aged adults. ObjectiveWe examined the association of milk, yogurt, cheese, cream, fluid dairy (milk + yogurt), and milk + yogurt + cheese intakes with bone mineral density (BMD) and 4-y percentage of change in BMD [▵%BMD; femoral neck, trochanter, and lumbar spine (LS)]. We further assessed whether these associations were modified by vitamin D supplement use in this cohort of older adults. MethodsFood-frequency questionnaire responses, baseline BMD (hip and spine, n = 862 in 1988–1989), and follow-up BMD (n = 628 in 1992–1993) were measured in the Framingham study, a prospective cohort study of older Caucasian men and women aged 67–93 y. Outcomes included baseline BMD and ▵%BMD. Dairy-food intakes (servings per week) were converted to energy-adjusted residuals, and linear regression was used, adjusting for covariates. These associations were further examined by vitamin D supplement use. ResultsThe mean age of the participants was 75 y. In the full sample, dairy-food items were not associated with BMD (P = 0.11–0.99) or with ▵%BMD (P = 0.29–0.96). Among vitamin D supplement users, but not among nonusers, higher milk, fluid dairy, and milk + yogurt + cheese intakes were associated with higher LS BMD (P = 0.011–0.009). Among vitamin D supplement users, but not among nonusers, higher milk + yogurt + cheese intakes were protective against trochanter BMD loss (P = 0.009). ConclusionIn this population of older adults, higher intakes of milk, fluid dairy, and milk + yogurt + cheese were associated with higher LS BMD, and a higher intake of milk + yogurt + cheese was protective against trochanter BMD loss among vitamin D supplement users but not among nonusers. These findings underscore that the benefits of dairy intake on the skeleton may be dependent on vitamin D intake.