Full Title: Dose Response Effects of a Blueberry-Enriched Diet on Net Bone Calcium Retention in Ovariectomized Rats
Journal: The FASEB Journal
Year of Publication: 2017
A diet rich in fruits and vegetables has been associated with increased bone mineral density (BMD) in postmenopausal women. This association is mainly attributed to anthocyanin rich fruits such as berries, grapes and plums. A blueberry-enriched diet has been shown to have bone health effects in animal models, not only in the adult postmenopausal model by attenuating bone loss, but also in the young rats by increasing accrual during growth. The effect of blueberry on calcium metabolism has not been elucidated. Our objective was to determine the effective dose of blueberry consumption to increase bone net calcium retention in ovariectomized rats.
Twenty 4-month old ovariectomized Sprague Dawley (SD) rats were administered a single dose of Ca-45 to pre-label their bones. After a 1-month equilibration period, the rats were put on a polyphenol free diet to determine baseline Ca-45 and total Ca excretion. Following baseline, rats went through four 10-day treatment periods on a blueberry-enriched diet (2.5%, 5%, 10% or 15% blueberry diet) in a random order. Each treatment period was followed by a 10-day washout period on a polyphenol free diet. 24h urinary Ca-45 excretion and total calcium were determined through beta scintillation counting and atomic absorption spectrometry, respectively. These values were used to create a Ca-45: Total Calcium ratio and plotted against time to determine changes in calcium excretion due to treatment versus non-treatment periods.
Of the four different doses, only the 5% BB diet had a significant effect (p-value = 0.0426) on net bone calcium retention increasing it by 25.6%. The 2.5% BB increased net bone calcium retention by 24%, but failed to reach significance (p-value=0.054). Interestingly, the higher doses of 10% and 15% BB did not have an effect on bone Ca retention, suggesting lower doses are more effective at increasing bone ca retention.
This study shows that a 5% blueberry diet increases bone net Ca retention by 25.6%. Higher doses did not have an effect on bone Ca retention. These results will serve to inform a chronic blueberry feeding study to determine the effects of blueberry on calcium balance and bone health in ovariectomized SD rats.
Link to Article: http://www.fasebj.org/doi/abs/10.1096/fasebj.31.1_supplement.793.20