The findings suggest the dried fruit provide an easy way of obtaining the necessary nutrients thought to prevent osteoporosis and inhibit bone breakdown characteristic of the condition.
The prevalence of age-related bone loss is greater in women than men, and in 25 to 30% of ageing women this loss results in major orthopaedic problems.
Calcium and vitamin D supplementation has been recommended as a safe, nutritional approach to help reduce bone loss.
In addition to diet and other lifestyle factors such as physical activity, there is evidence to suggest functional foods can improve growth and development as well as reduce the risk of chronic diseases such as osteoporosis.
The new research is all the more compelling as women can lose up to 20% of their bone density during the five to seven years following menopause.
"Participants from our study maintained their bone mineral density by eating five to six dried plums per day, which is a very exciting finding as this can easily be achieved by snacking on dried plums or incorporating them into recipes." said Dr Shirin Hooshmand, lead researcher on the study and associate professor at the School of Exercise and Nutritional Sciences at San Diego State University.
Proving plum’s efficacy
A total of 48 women with low bone density aged 65–79 years old were randomly assigned into one of three treatment groups for six months: 50 g of dried plum; 100 g of dried plum; or control.
Total body, hip and lumbar bone mineral density (BMD) were evaluated at the beginning of the study and at six months.
Molecules in the blood that can be measured to assess health were recorded at baseline, three months and six months, as were calcium, phosphorous and vitamin D levels.
Researchers found both doses of dried plum were able to prevent the loss of total body bone mineral density (BMD) compared to the control group.
TRAP-5b, a marker of bone resorption, decreased at three months and this was sustained at six months in both 50 and 100 g dried plum groups.
There were no significant changes in bone-specific alkaline phosphatase (BAP) activity for either of the dried plum groups. The enzyme BAP is a sensitive and reliable indicator of bone metabolism
Among the functional foods shown to have bone-protective effects, dried plum is uniquely able to prevent and reverse bone loss in rat models of osteoporosis.
In human studies, a short-term clinical study demonstrated 100 g/day of dried plum over three months improved biomarkers of bone formation in postmenopausal women.
Hooshmand’s team also carried out a 12-month study in which postmenopausal women consumed 100 g of dried plum daily. This study also demonstrated the ability of dried plum to completely prevent the loss of bone mineral density.
Explaining plum’s potency
“Age-related bone loss, including that which occurs in postmenopausal women, may be partly associated with decreased production of certain growth factors such as insulin-like growth factor-1 (IGF-1),” the study noted.
Another mechanism by which dried plums may prevent bone loss is via their strong antioxidant properties.
One study showed dried plum increased circulating levels of glutathione peroxidase which is a strong enzymatic antioxidant.
Although the exact mechanisms of action are still unknown, the study’s findings indicate dried plum's potency.
“Aside from the scarcity of literature addressing the mechanisms of action by which dried plum prevents bone loss, clinical studies are needed to demonstrate whether more reasonable amounts of dried plum can also be effective in preventing bone loss.
"These results suggest that a lower dose of dried plum (i.e. 50 g) may be as effective as 100 g of dried plum in preventing bone loss in older, osteopenic postmenopausal women. This may be due, in part, to the ability of dried plums to inhibit bone resorption.”
Source: Osteoporosis International
Published online ahead of print, DOI 10.1007/s00198-016-3524-8
“The effect of two doses of dried plum on bone density and bone biomarkers in osteopenic postmenopausal women: a randomized, controlled trial.”
Authors: S. Hooshmand & M. Kern & D. Metti & P. Shamloufard & S. C. Chai & S. A. Johnson & M. E. Payton & B. H. Arjmandi