Calcium, dairy products and osteoporosis

Osteoporosis is a multifactorial disorder in which nutrition plays a role b ut does not account for the totality of the problem. 139 papers published s ince 1975 and describing studies of the relationship of calcium intake and bone health are briefly analyzed. Of 52 investigator-controlled calcium int ervention studies, all bur two showed better bone balance at high intakes, or greater bone gain during growth, or reduced bone loss in the elderly, or reduced fracture risk. This evidence firmly establishes that high calcium intakes promote bone health. Additionally, three-fourths of 86 observationa l studies were also positive, indicating that the causal link established i n investigator-controlled trials can be found in free-living subjects as we ll. The principal reason for failure to find an association in observationa l studies is the weakness of the methods available for estimating long-term calcium intake. While most of the investigator-controlled studies used cal cium supplements, six used dairy sources of calcium: all were positive. Mos t of the observational studies were based on dairy calcium also, since at t he time the studies were done, higher calcium intakes meant higher dairy in takes. All studies evaluating the issue reported substantial augmentation o f the osteoprotective effect of estrogen by high calcium intakes. Discussio n is provided in regard to the multifactorial complexity of osteoporotic re sponse to interventions and to the perturbing effect in controlled trials o f the bone remodeling transient, as well as about how inferences can validl y be drawn from the various study types represented in this compilation.