The acid-base hypothesis: diet and bone in the Framingham Osteoporosis Study.

BACKGROUND: There continues to be considerable debate about the role of acid vs. basic components of the diet on the long-term status of bone mineral density.

AIM: In a set of two analyses, we examined the effect of components in the diet thought to have basic effects (magnesium, potassium, fruit, vegetables) and acid effects (protein) on bone mineral density in an elderly cohort.

METHODS: Bone mineral density of participants in the Framingham Osteoporosis Study was measured at three hip sites and one forearm site at two points in time, four years apart. At the time of baseline measurement, participants ranged in age from 69-97 years. Dietary intake was assessed at baseline by food frequency questionnaire.

RESULTS: As hypothesized, magnesium, potassium, fruit and vegetable intakes were significantly associated with bone mineral density at baseline and among men, with lower bone loss over four years. In contrast to the hypothesis, higher rather than lower protein intakes were associated with lower bone loss.

CONCLUSION: Together these results support the role of base forming foods and nutrients in bone maintenance. The role of protein appears to be complex and is probably dependent on the presence of other nutrients available in a mixed diet. A balanced diet with ample fruit and vegetables and adequate protein appears to be important to bone mineral density.