The latest study, published in the Journal of the Orthopaedic Research Society - Spine, was led by Bernard Halloran, PhD, Professor Emeritus, University of California - San Francisco (UCSF) and Xuhui Liu, MD, San Francisco Veterans Affairs Medical Center, Department of Veterans Affairs and the Department of Orthopedic Surgery, University of California - San Francisco.
The findings from the mouse study show a diet high in dried plum (DP) completely prevents bone loss associated with spinal cord injury (SCI), while also restoring some of the bone loss.
"This evaluation is particularly important as individuals who suffer SCI experience extremely rapid bone loss," said Liu. "The SCI-related bone loss then leads to an increased risk of fractures, osteoporosis, and overall morbidity and mortality."
The research, funded by the California Dried Plum Board as well as the National Institute of Arthritis and Musculoskeletal and Skin Diseases, involved two parts: prevention and recovery. In the prevention experiment, the researchers looked at dietary supplementation with dried plum for mitigating the loss of bone induced by SCI. For the recovery experiment, the team examined whether a dried plum diet could restore bone loss after SCI.
Part I: Prevention
In the prevention evaluation, mice underwent SCI and were fed a diet containing 25% dried plum by weight or a control diet for up to four weeks. In vivo microCT scanning was performed three times, including at baseline before SCI, as well as at two and four weeks after SCI.
The findings revealed that dried plum prevents SCI-related bone loss. when compared to the control diets, the dried plum diet completely prevented bone loss. In contrast, the control group diet resulted in 53% loss of bone volume at two weeks and 71% of bone loss volume at four weeks-post injury.
Part II: Recovery
In the recovery experiment, mice were divided into groups and fed a control diet for two or four weeks. Another group was fed a control diet for two weeks to allow bone loss and then switched to the dried plum diet for an additional two weeks. The findings show that after two weeks, the dried plum diet partially restored bone that had already been lost to SCI. Another finding was bone strength was greater in the mice that switched to the dried plum diet when compared to the mice who were fed the control diet for four weeks.
Liu explained how dried plum might restore some SCI-related bone loss:
"There are two types of cells involved with bone metabolism - osteoblasts and osteoclasts. Osteoblasts help to build new bone, while osteoclasts are essentially 'bone eaters,'" and function to tear down bone," said Liu. "At this time, we believe that dried plum functions to inhibit the bone-eating osteoclasts and this results in more bone."
The researchers say it’s unclear what bioactive compounds in dried plum are responsible for the beneficial effects on bone health, but point to the plums polyphenol content as a likely culprit.
The report explained that non-polyphenolic compounds in DP may also be involved, such as vitamin K and manganese. Both nutrients are recognized as contributing to the maintenance of normal bone. Future work will focus on identifying and isolating the bioactive factors in dried plums.
"In summary, dietary supplementation with dried plum or products derived from dried plum may prove to help slow the loss of bone induced by SCI, as well as to improve other bone-related conditions," said Halloran. "The consistency of bone response to dried plum is remarkable, especially considering that dried plums are a whole food approach to healthy eating, as well as being readily available, economical, safe and - by all indications - effective in supporting healthy bones."
The gut-bone axis
The gut microbiome is a key regulator in bone health. Research suggests that changes in microbiota composition may prevent or reverse bone loss with prebiotic and probiotic supplementation. One way microbes influence organs is through the production of metabolites that diffuse from the gut into the systemic circulation. Recently, short-chain fatty acids (SCFAs) have emerged as key regulatory metabolites produced by the gut microbiota.
The report explained that DP contains prebiotic factors and changes in the microbiome have been linked to changes in mineral metabolism. “Intestinal calcium bioavailability has also been shown to be associated with changes in short chain fatty acids (SCFA), although dietary consumption of plum has been reported to have no effect on SCFA. Other factors reported to affect bone, such as vitamin K (menaquinone), are produced in the intestine and synthesis is altered by the composition of the intestinal microbiota. Collectively, these observations suggest that the effects of DP on bone in SCI patients may be mediated through changes in the gut microbiome,” explained the authors.
Scientists are excited
"We are seeing an exciting 'dried plum effect' on bones," said Halloran. "In a variety of unique research scenarios, dried plum is consistently associated with a favorable bone response. No other compound appears to have the same degree of positive impact."
“In conclusion, dietary supplementation with DP can prevent bone loss in an acute model of SCI, and restore a fraction, but not all, of the bone that has already been lost in mice following SCI,” noted the authors.
Previous clinical research has demonstrated a favorable bone response to prunes among post-menopausal women, along with animal-based research that shows a similar positive response among those exposed to radiation, such as astronauts in space.
Source: Journal of the Orthopaedic Research Society - Spine
“Dried plum mitigates spinal cord injury‐induced bone loss in mice”
Authors: X. Liu et al.