A Grape-Enriched Diet Increases Bone Calcium Retention and Cortical Bone Properties in

TLDR: This study of ovariectomized rats indicates that the consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality.

Abstract: Background: Grapes and their associated phytochemicals have been investigated for beneficial effects on cardiovascular health, cancer prevention, and other chronic diseases, but the effect of grape consumption on bone health has not been fully determined. We previously found short-term benefits of grape products on reducing bone turnover in ovariectomized rats. Objective: The objective of this study was to determine the long-term benefits of a grape-enriched diet on bone in ovariectomized rats. Methods: Rats were ovariectomized at 3 mo of age and were administered a single dose of 45 Ca to prelabel bones at 4 mo of age. After a 1-mo equilibration period, baseline urinary 45 Ca excretion was determined. Rats (n = 22/group) were then randomly assigned to a modified AIN93M diet containing 25% freeze-dried grape powder or to a control diet for 8 wk. Urinary 45 Ca excretion was monitored throughout the study to determine changes in bone 45 Ca retention. Calcium balance was assessedafter 1 and 8 wk with the experimental diets, and a calcium kinetic study was performed at 8 wk. After 8 wk, femurs were collected for micro-computed tomographic imaging, 3-point bending, and reference point indentation. Results: Rats fed the grape-enriched diet had 44% greater net bone calcium retention than did rats fed the control diet. There were no differences in calcium balance due to diet at either week 1 or week 8, but there was a significant increase in net calcium absorption (10.6%) and retention (5.7%) from week 1 to week 8 in the grape-enriched diet group only. Grapeenriched diet‐fed rats had 3% greater cortical thickness and 11% greater breaking strength. There were no differences in femur bone mineral density, trabecular microarchitecture, or reference point indentation variables due to diet. Conclusion: The consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality. J Nutr doi: 10.3945/jn.114.198598.