Osteoporosis bone loss reversed by prunes

Research just published in PLoS One (Public Library of Science) offers evidence that prunes, now fashionably known as dried plums, not only help to reduce bone loss but stimulate new bone growth. I suspect that most clinicians reading this also endeavor to educate their patients that osteoporosis is not a calcium deficiency disorder (osteomalacia). As the authors state:

"Bone remodeling is a dynamic process involving the orchestration of bone resorption, formation and mineralization. When the balance between these anabolic and catabolic events is altered or disrupted, skeletal quality can be compromised, resulting in an increase in fracture risk."

Although anti-resorptive agents such as bisphosphonates (Fosamax, etc.) inhibiting the catabolic activity of osteoclasts (cells that resorb old bone to make way for new), partly by killing them off they don't restore or support the protein matrix ('scaffolding') that gives resilience to which calcium and other minerals attach. Key factors are inflammation and an anabolic hormonal milieu, both of which may be postively affected by dried plums (prunes). The authors also note:

"During the first 5–10 years after menopause, a physiological state exists in which bone turnover (i.e., both resorption and formation rate) is accelerated with the catabolic activity of osteoclasts favored over the anabolic activity of osteoblasts. The classic model used to study post-menopausal bone loss has been the ovariectomized (OVX) rat and mouse. This model has provided much insight into the effects of ovarian hormones, such as estrogen, progesterone, and follicle stimulating hormone (FSH), and their direct influence on bone metabolism. Aside from these more direct effects on bone cells, estrogen’s more recently recognized regulatory role in cellular inflammatory and oxidative processes has resulted in an increased interest in targeting these pathways for therapeutic purposes."

The anti-inflammatory effects of dried plums and other fruits has been known for some time. The ability of dried plums to increase glutathione activity is of special significance because of the latter's anti-inflammatory and immune regulating properties.

"Natural compounds such as those found in many fruits and vegetables exert anti-inflammatory and anti-oxidant activity that have the potential to attenuate bone loss. The up-regulation of antioxidant systems (i.e., glutathione peroxidase or GPx) has been shown to suppress bone resorption associated with estrogen deficiency. Dried plums (Prunus domestica L.), which have a high polyphenolic content and oxygen radical absorbance capacity (ORAC) score, have been shown to protect against and reverse bone loss in gonadal hormone deficient rat and mouse models of osteoporosis. These studies with dried plum have consistently demonstrated that dried plum improves bone mineral density (BMD), trabecular bone microarchitecture, and biomechanical properties...Although the mechanism has yet to be fully described, dried plum’s ability to restore bone mass appears to be associated with an increase or maintenance of bone formation in conjunction with suppression of bone resorption. These promising findings have led to the question of whether or not other dried fruits with known anti-oxidative properties can reverse bone loss to the extent of dried plum."

So they fed adult osteopenic ovariectomized (OVX) C57BL/6 mice were either a control diet or a diet supplemented with dried plum, apple, apricot, grape or mango for 8 weeks, after which they measured whole body and spine bone mineral density, bone biomechanical properties, plasma antioxidant capacity, glutathione activity and relevant RNA expression, along with osteoblast and osteoclast differentiation, activity and apoptosis. And the prunes came out on top of the heap:

"The bone densitometry data confirm that dried plum, and to a lesser extent apricot and grape, have the ability to protect bone in osteopenic OVX C57BL/6 mice. Evaluation of the bone microarchitectural parameters revealed that dried plum prevented the loss of trabecular bone in the proximal tibia and was the only fruit to exert an anabolic effect on the trabecular bone of the vertebra. These alterations in the vertebral trabecular bone of animals receiving dried plum coincided with improved biomechanical properties, including bone strength and stiffness. These improvements in the biomechanical and structural properties suggest that dried plum supplementation results in enhanced bone quality."

Moreover, and of great interest:

"Due to the apparent novelty of dried plum to not only prevent catabolic activity but also have anabolic effects on bone at some skeletal sites, the relative mRNA abundance of key genes involved in the regulation osteoblast and osteoclast differentiation and activity were assessed. Dried plum decreased osteoclastogenesis through the attenuation of Nfatc1 gene expression, while simultaneously up-regulating osteoblast activity by enhancing Col1a1 mRNA. This data is consistent with previous reports of dried plum’s dual anti-resorptive and anabolic actions which represents an uncoupling of bone turnover in favor of accrual of new bone tissue...Interestingly, dried apple also decreased Nfatc1 and Col1a1 transcription, but these alterations in mRNA were not accompanied with beneficial effects on BMD or trabecular bone volume at this time point. These findings raise the issue that dried plum has additional effects, perhaps in part tied to its influence on antioxidant systems that ultimately lead to its unique ability to restore bone."

Way to go prunes! The authors conclude:

"In summary, this is the first study to demonstrate the extent to which dried plum restores bone in osteopenic OVX animals compared to apple, apricot, grape and mango supplementation. The potency of dried plum was unique in the sense that it not only prevented bone loss, but also induced an anabolic response in the vertebra. These structural changes coincided with local up-regulation of indicators of osteoblast activity and the down-regulation of osteoclastogenesis. These alternations in mediators of bone metabolism occurred in conjunction with enhanced systemic GPx activity."