Can prunes reverse bone loss?

By Jorisna Bonthuys

A growing body of research suggests that eating prunes could improve bone health in postmenopausal women who have low bone mass. In some cases, it might even reverse bone loss caused by osteoporosis.

Osteoporosis is a condition that refers to the weakening of bones outside of a normal range, to a point at which peoples’ risk of getting a bone fracture increases, particularly in the spine, hip and wrist. Donn Zea, the executive director of the California Prune Board, presented some results and preliminary findings of the latest cutting-edge research on this topic at the annual congress of the International Prune Association (IPA) held in Cape Town from 28-29 October 2019.

Due to its prevalence worldwide, osteoporosis is now considered a serious public health concern. As the world’s demographic shift to an older population continues, more people will be diagnosed with osteoporosis. It is estimated that more than 200 million people suffer from the disease across the globe.

A current study, funded by the IPA and the Californian Prune Board, is the largest clinical trial to date. The researchers are investigating the relationship between eating prunes and the maintenance of bone health in postmenopausal women. This study builds on the results of pre-clinical and clinical trials over the past two decades. Final results aren’t expected until the end of 2021. But already there are promising results. Zea highlighted: “There are once again indications that prunes may help prevent bone loss and preserve bone structure in postmenopausal women. This can help to reduce the risk of fractures (related to osteoporosis) happening.”

In one case, a 55-year-old woman who completed the study as part of the control group (the group that did not eat prunes) had lost bone density as measured by three different scans at the beginning and end of the period. She decided to consume 50 g prunes per day, on her own volition. Four months later, the scientists who monitored her progress reported a marked improvement in her bone mineral density. During this period, her spine bone mineral density increased by 7,9%, returning to levels above when she started to participate in the study.

“These results were so promising that the primary investigator presented them to members of the American Society for Bone and Mineral Research in September,” Zea said. Prof Mary Jane De Souza from the Department of Kinesiology and Physiology at Penn State University (in the USA) is leading this research project. The results suggest that a non-pharmacological (dietary) intervention of 50 g of prunes daily, in addition to daily supplementation of calcium and vitamin D, may have a greater impact on bone mineral density than calcium and Vitamin D supplementation alone in postmenopausal women with osteopenia. This condition is often a precursor of osteoporosis.

The research shows that eating prunes improve the effect of osteoblasts (the bone-building cells) and reduces the effect of osteoclasts (the cells responsible for its resorption), Zea explained. Osteoblasts are needed for bone synthesis and mineralisation, both during the initial formation of bone and, during bone remodelling. Bone is a dynamic type of tissue that keeps changing throughout your life — new bone is made and old bone is broken down. In postmenopausal women, the declining rates of the hormone estrogen can increase the rate of bone resorption (when bone is broken down). The older you get, the greater your risk of developing osteoporosis.

Zea said at this stage it is still a mystery how exactly prunes are improving bone health. “While we don’t understand the exact mechanism in which this occurs, it’s very likely a synergistic effect of source nutrients alongside some powerful polyphenols (plant compounds packed with antioxidants).”

Besides this study, more work is underway to explore the links between eating prunes and bone health in men as well as younger women using steroidal contraceptives, where a loss in bone mineral density has been associated. Research is also underway to investigate the effects of eating prunes on the bone density of people with spinal injuries and those who have suffered wrist fractures. According to scientists, women are much more likely to develop osteoporosis than are men. The reduction of estrogen levels in women during menopause is considered one of the strongest risk factors for developing this condition.

Dappie Smit, Hortgro’s general manager responsible for dried fruit, says efforts are underway to understand the benefits of prunes on bone health and to address lifestyle diseases. “The people living in Agen in southwest France eat plenty of foie gras, drink lots of red wine, eat prunes and enjoy low levels of heart disease. This is called the ‘French paradox’ and led to research projects on the effects of prunes on heart disease, digestive disorders, weight control and efforts to promote bone density.”

In recent years, the use of non-pharmacological interventions to reverse low bone density has gained lots of traction. These and other research efforts help ensure that producers remain competitive, Smit indicated. The bone density research is already in the clinical phase, meaning it is being tested on groups of people while their bone density and other markers are being monitored. “Seeing that most cancer treatments also affect bone density, the research could also make a positive contribution in this regard,” Smit said. “The study also helps unlock a new understanding of the health benefits of prunes and ways to communicate about it to younger and health-conscious consumers,” he indicated.

Caption: Attending the IPA Congress in Cape Town – Pedro-Pablo Diaz (Chile), Chris Krone (IPA Chairman) and Dappie Smit (Hortgro) and Donn Zea (USA).