Written by Harold Oster, MD. Results show that blueberry powder intake may increase the calcium retention of bone in postmenopausal women.
Osteoporosis is a common disease of the skeleton, characterized by a decrease in bone mass. Osteoporosis increases bone fragility and predisposes to fractures, with the highest risk being in postmenopausal women. Diagnosis of osteoporosis is typically based on a bone mineral density (BMD) of 2.5 standard deviations below the mean for young normal women1. Because of the slow improvement of BMD in response to therapy, other tests have been developed. Biomarkers of bone turnover change more rapidly and are predictive of response to therapy and fracture risk. These include insulin-like growth factor-1 (IGF-1) and its binding protein (IGFBP-3,) procollagen type 1 N- terminal propeptide (P1NP), cross-linked C-telopeptide (CTx), sclerostin, osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL) and their ratio, as well as urinary N-terminal telopeptide (NTx.2) A more rapid assessment of response to therapy is the calcium retention of bone, as measured by the 41Ca:Ca (total) ratio in urine at least 150 days after administration of the 41Ca tracer. The urinary 41Ca comes directly from bone, and the ratio of 41Ca:Ca in the urine falls after effective therapy, signifying calcium retention of bone3. Blueberries are rich in polyphenols and other antioxidants shown in animal and human studies to have beneficial effects on bone mass.
Joanna K. Hodges et al. studied the effect of three different doses of blueberry powder on the retention of calcium in bone in postmenopausal women. A preclinical study was performed on rats to validate the crossover method and its effects on 41Ca and determine the appropriate dosing of blueberry powder. In a controlled manner, twenty ovariectomized rats were given 41Ca. After an equilibration period, they were randomly fed three different doses of blueberry powder for ten days followed by a washout period, an approach similar to the clinical study to follow on postmenopausal women. Changes in 41Ca:Ca levels in the rats validated the clinical study design and aided the authors in choosing appropriate blueberry powder doses for the human participants.
Thirty-five healthy women from the Lafayette, IN area, at least four years post natural or surgical menopause, were recruited, and 18 women met the inclusion criteria. The women received 50-nCi of 41Ca intravenously. After five months of equilibration, they were randomly assigned to a sequence of intervention periods of a low (17.5g/d), medium (35g/d), or high (70g/d) dose of blueberry powder. Each intervention period lasted six weeks and was followed by a non-intervention period. Urinary calcium was measured weekly during the intervention periods and every three weeks during the washout intervals. Bone density was measured at baseline, and BMI was calculated at the end of each study period. Participants were instructed on foods to avoid that might affect the study’s results and completed four-day dietary records several times throughout the study. Urinary polyphenolics were tested at the end of each intervention to assess adherence to the protocol. Before each intervention, blood and urine were collected to assess for serum calcium and vitamin D and the bone biomarkers listed above.
The authors noted the following:
- Thirteen participants completed the study.
- The participants’ baseline characteristics were comparable to the US female population of similar age.
- Dietary intake of relevant nutrients was comparable to mean intakes in the United States, and relevant baseline lab testing was normal.
- BMI of the participants remained stable throughout the study,
- Participants consuming the low and medium doses of blueberry powder for six weeks retained significantly more calcium in bone compared with no treatment (5.6% and 4.5% increase, respectively).
- During the high-dose intervention period, there was no significant association between blueberry powder intake and calcium retention.
- RANKL, a marker of bone resorption, was reduced after the medium-dose intervention.
- The serum calcium, vitamin D, and other markers of bone resorption did not change significantly in the intervention periods.
Results of the study suggest that low to moderate intake of a blueberry powder supplement increases the calcium retention of bone. Limitations of the study include a small sample size and lack of racial diversity among the participants.
Source: Hodges, Joanna, Sisi Cao, Pamela Lachcik, Munro Peacock, George McCabe, Linda McCabe, Dennis Cladis, Mario Ferruzzi, Berdine Martin, and Connie Weaver. “Moderate consumption of freeze-dried blueberry powder increased net bone calcium retention in healthy postmenopausal women: A randomized crossover trial.” Current Developments in Nutrition 4 (2020): 4140032.
© 2023 The Authors. Published by Elsevier Inc. on behalf of American Society for Nutrition. This is an open access article under the CC BY license (http://
creativecommons.org/licenses/by/4.0/).
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Posted July 12, 2023.
Harold Oster, MD graduated from medical school in Miami, Florida in 1992 and moved to Minnesota in 2004. After more than 25 years of practicing Internal Medicine, he recently retired. Dr. Oster is especially interested in nutrition, weight management, and disease prevention. Visit his website at haroldoster.com.
References:
- Clynes MA, Harvey NC, Curtis EM, Fuggle NR, Dennison EM, Cooper C. The epidemiology of osteoporosis. Br Med Bull. May 15 2020;133(1):105-117. doi:10.1093/bmb/ldaa005
- Eastell R, Hannon RA. Biomarkers of bone health and osteoporosis risk. The Proceedings of the Nutrition Society. May 2008;67(2):157-62. doi:10.1017/s002966510800699x
- Weaver CM, Martin BR, Jackson GS, McCabe GP, Peacock M, Wastney M. Calcium-41: a technology for monitoring changes in bone mineral. Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA. Apr 2017;28(4):1215-1223. doi:10.1007/s00198-016-3849-3
