Dried Plums and Osteoporosis

Jacob Schor

Naturopathic Doctor

Fellow American Board of Naturopathic Oncology

 

Dried plums may soon be added to our list of osteoporosis treatments. I’m not making this up.  Dried plums are the things most of us call prunes.  I’ll get to the research momentarily.  First we have to explain this dried plum versus prune nomenclature.

The things we call prunes are, as of a June 2000 FDA decision, now called ‘dried plums.’ The California Prune Board (now the California Dried Plum Board) has ‘rebranded’ prunes as something stylish that young people can eat.  Part of this rebranding effort is this name change. Their goal is to change the public perception that prunes are something that old people need to eat to prevent constipation because this hurts prune sales to anyone younger than baby boomer age.  The goal is that young people should think that dried plums contain oodles of antioxidants in them, not that they are great laxatives. This scientific data that prunes are helpful for osteoporosis, while fascinating to people like me, is probably not what the Prune Board wants to hear.  Whoops, I mean Dried Plum Board. It’s just another thing that will reinforce that ‘prunes are for old people’ image they are working so hard to change.  

 

A Brief Historic Detour:

Plums originally came from the Caucasus Mountains bordering the Caspian Sea. In the 12th century, the Crusaders brought damson plum trees back to Europe from Syria. The story goes that, at some point, the monks of the Clairac Abbey in France crossed a damson tree with a local plum and created a new variety that they called the Ente plum.  The name comes from the old French word "enter," meaning, "to graft." The Clairac monks figured out how to preserve their plums by drying them in the sun. This Abbey became famous throughout France for its prunes.

In 1856 a Frenchman named Louis Pellier secretly smuggled cuttings from these Clairac plum trees out of France and brought them to California.  Trees from these cuttings became the start of the California prune industry.  California now produces twice as many dried plums as the rest of the world combined: approximately 99 percent of the U.S. supply and 70 percent of the world supply.

               

The news that prunes could help osteoporosis started to come out right about when this name change was initiated.  The first paper that touched on this was published in 2001 in the Journal of the American College of Nutrition.  “The role of phytoestrogens in the prevention and treatment of osteoporosis in ovarian hormone deficiency.”   This paper focused on soy isoflavones, but it touched on both flax and ‘dried plums’ as also having estrogen-like effects.  [The author of this paper, Bahram Arjmandi, has gone on to co-author an additional eight  papers looking at the effect of prunes on bone but always calls them dried plums.]

The name change wasn’t universal back then.  A review paper by Stacewicz-Sapuntzakis et al., also published in 2001, still called them prunes, as it reviewed their potential as a functional food in preventing heart disease and cancer.

A year later in 2002, Arjmandi reported the results of his first human trial with dried plums and osteoporosis.  Arjmandi has consistently used the term dried plums in each of his 5 studies on the subject.  In an earlier study he found that dried plums were,  “ … highly effective in modulating bone mass in an ovarian hormone-deficient rat model of osteoporosis.”  In other words, they had removed the ovaries from a bunch of rats, a sure fired method to give the rats osteoporosis, but if they fed the rats lots of prunes, they didn’t get osteoporosis.  Arjmandi and his colleagues at the University of Oklahoma set up another study, “…to examine whether the addition of dried plums to the diets of postmenopausal women positively influences markers of bone turnover.”  Fifty-eight post-menopausal women took part in the study and were randomly assigned to eat either 100 grams of prunes or 75 grams of dried apples every day.  None of the women were on hormone replacement therapy.  Biochemical markers of bone were measured before and after treatment. 

The prunes but not the apples, “…significantly increased serum levels of insulin-like growth factor-I (IGF-I) and bone-specific alkaline phosphatase (BSAP) activity.”  High levels of both of these chemicals are associated with faster bone formation.   Serum and urinary markers of bone resorption, however, were not affected by either eating apples or prunes.  Although bone breakdown didn’t change, the process of making new bone increased in the prune eaters.    This gets our attention because the common drugs used to treat osteoporosis focus on the other side of the equation; they slow bone resorption.  It’s often been argued that though this maintains bone density measured on scans,  slowing resorption leaves the bones denser but also brittle.

Arjmandi went back to feeding rats to figure out exactly what was going on and had another interesting paper published in the November 2005 issue of Menopause.   This paper again looked at the effect of prunes in female rats who without ovaries.   They fed three different concentrations of prune to the rats and changes in bone density and strength were measured. 

“Dried plum, as low as 5%, was effective in restoring femoral and tibial bone density.  Dried plum increased lumbar bone density as well, with HD (high dosage of prunes) achieving a statistical significance. The increase in femoral bone density of dried plum-fed rats resulted in improved bone quality as indicated by 6.9% and 6.0% improvement in overall yield and ultimate force, respectively. Varying doses of dried plum were also able to significantly improve trabecular microarchitectural properties in comparison with ovariectomized controls.”   

This was a big thing.  As the authors wrote:

Loss of bone volume accompanied by loss of trabecular connectivity is generally believed to be an irreversible process, but our observations suggest that dried plum improves trabecular microstructure of tibia after losses have already occurred.”

 

 

In 2006, the journal Bone published the results of a somewhat similar study but using used male rats instead of females as subjects. The rats were castrated; a process which should trigger osteoporosis. Castrate rats are often used as a research model for aging men.  In men over 40, testosterone levels decrease by about one per cent per year, leading to weaker muscles and thinner bones. Castrating the rats mirrors what happens in men, just more abrupt and easier to study.

These testosterone deprived rats were divided into groups and fed either low doses, medium doses  (MD) or high doses (HD) of prune extracts.  At the end of the treatment period, both the “MD and HD of dried plum completely prevented the ORX-induced [castration induced] decrease in whole body, femur, and lumbar vertebra bone mineral density (BMD).”

Various chemical markers of bone loss and bone strength improved in the castrated rats, even on the low doses of prunes. 

“We conclude that dried plum prevents osteopenia in androgen deficient male rats, and these beneficial effects may be attributed in part to a decrease in osteoclastogenesis via down-regulation of RANKL and stimulation of bone formation mediated by IGF-I.”

Measurement of bone resorption using the biomarker deoxypyridinoline (DPD) showed that total DPD rose by about 36 per cent in the castrated rats after 90 days, indicating that the bones were still being weakened by resorption. However, dietary supplementation with dried plums appeared to decrease this resorption, said the researchers, and excretion of DPD in the urine was 57 per cent lower in the high-dose group than the control diet.” Danie

In 2007, Osteoporosis published a follow up study.  In this study, again using castrated rats as an experimental model of osteoporosis, the benefit of eating prune extracts was compared to the effect of doses of parathyroid hormone.  The dried plums (DP) helped restore bone mass in the rats but not as effectively as parathyroid hormone (PTH) did.

Arjjmandi has moved from Oklahoma to Florida and in early 2007, Florida State University researchers launched a randomized clinical trial that will reproduce the early Oklahoma women and prune study on a larger scale.  The study will again compare the effects of eating either prunes or dried apples on the bone mineral density of post-menopausal women.

There have been two additional papers of interest published in just the last few months. The first, is in the May 18 issue of the Journal of Nutrition and Biochemistry, is titled, “Dried plum polyphenols attenuate the detrimental effects of TNF-alpha on osteoblast function coincident with up-regulation of Runx2, Osterix and IGF-I.”

This in vitro research began to detail the chemical explanations as to how prune extracts exert their beneficial effects. 

The second paper, “Dried Plum Polyphenols Inhibit Osteoclastogenesis by Downregulating NFATc1 and Inflammatory Mediators” again focuses on biochemical mechanisms of action.

 

There are manufacturers out there watching this research closely and hoping to introduce concentrated prune extracts, at this point in time, eating the fruit is still the best way to benefit from prunes.

The amount of dried plum used in these studies is equivalent to eating about 10-11 prunes per day.  It is true that prunes do have a mild laxative effect though the reason why is still poorly understood.  Some credit for this effect is attributed to the high sorbitol content but there are other factors at work.  The high sorbitol content is also why prunes taste much sweeter than their actual glycemic effect; sorbitol though it tastes sweet like sugar isn’t absorbed into the body.  We can almost consider prunes as a ‘lower calorie sweetener’ compared to regular sweeteners like sugar.  This laxative effect may be too much for some people but a surprising number of people do fine eating this many prunes regularly.

In some countries prunes are often added to meat dishes.  The prunes are a concentrated source of antioxidants that they prevent development of off flavors in the meat from overcooking.  This is similar to the effect seen in adding cherries to meat, something we’ve written about in the past.  The antioxidants in both cherries and prunes decrease the formation of cancer causing chemicals during the cooking process.  These fruits are actually cousins, both belonging to the same Prunus family of fruit trees.

I admit when I first chanced upon this information, I didn’t believe what I was reading.  I thought that the one line mention I happened upon was a leftover April Fools joke.  My biased assumption was the result of my sharing the public’s perceptions of prunes.  In a way prunes are the ‘snowboarders of fruits.’  It’s easy to make them the object of a bad joke.  Perhaps the attempt to rebrand them as dried plums is a good idea after all.  Prunes, or better, dried plums, now deserve a place on our list of interventions for patients at risk or with osteoporosis. 

Cherry and Barbecuing Meat newsletter: http://denvernaturopathic.com/barbecueandCherries.htmhttp://denvernaturopathic.com/barbecueandCherries.htm

It's not all good news.  Prunes may be a problem for people with cancer or even at risk of cancer.  Before starting on a prune diet, read our follow up article posted at:

http://denvernaturopathic.com/prunesIGFcancer.htm

References:

J Am Coll Nutr. 2001 Oct;20(5 Suppl):398S-402S; discussion 417S-420S.  

    The role of phytoestrogens in the prevention and treatment of osteoporosis in ovarian hormone deficiency.

    Arjmandi BH.

    Department of Nutritional Sciences, Oklahoma State University, Stillwater 74078, USA. arjmand@okstate.edu

    Ovarian hormone deficiency is a major risk factor for osteoporosis in postmenopausal women. Hormone replacement therapy (HRT) is perhaps the most effective treatment, as it has been demonstrated to both reduce the rate of bone loss and risk of fracture, including hip fracture. However, not all women who may benefit from HRT are willing to initiate this treatment due to fear of cancer and contraindications. Other therapeutic agents currently available are also associated with certain adverse effects. As a result, postmenopausal women are more inclined to use natural remedies to alleviate postmenopausal symptoms and help reduce their risk for chronic diseases such as osteoporosis. Recent reports support the notion that certain bioactive constituents, e.g., phytoestrogens, in plants play a role in maintaining or improving skeletal health. The main consumable plant sources of phytoestrogens include isoflavones and lignans found mainly in soybeans and flaxseed, respectively. Although this paper primarily focuses on the effects of soy protein or its isoflavones on bone, additional statements regarding the role of flaxseed and dried plums, a rich source of polyphenols, with respect to bone will be made.

Crit Rev Food Sci Nutr. 2001 May;41(4):251-86.Links

    Chemical composition and potential health effects of prunes: a functional food?

    Stacewicz-Sapuntzakis M, Bowen PE, Hussain EA, Damayanti-Wood BI, Farnsworth NR.

    Department of Human Nutrition and Dietetics, University of Illinois at Chicago, USA.

    Prunes are dried plums, fruits of Prunus domestica L., cultivated and propagated since ancient times. Most dried prunes are produced from cultivar d'Agen, especially in California and France, where the cultivar originated. After harvest, prune-making plums are dehydrated in hot air at 85 to 90 degrees C for 18 h, then further processed into prune juice, puree, or other prune products. This extensive literature review summarizes the current knowledge of chemical composition of prunes and their biological effects on human health. Because of their sweet flavor and well-known mild laxative effect, prunes are considered to be an epitome of functional foods, but the understanding of their mode of action is still unclear. Dried prunes contain approximately 6.1 g of dietary fiber per 100 g, while prune juice is devoid of fiber due to filtration before bottling. The laxative action of both prune and prune juice could be explained by their high sorbitol content (14.7 and 6.1 g/100 g, respectively). Prunes are good source of energy in the form of simple sugars, but do not mediate a rapid rise in blood sugar concentration, possibly because of high fiber, fructose, and sorbitol content. Prunes contain large amounts of phenolic compounds (184 mg/100 g), mainly as neochlorogenic and chlorogenic acids, which may aid in the laxative action and delay glucose absorption. Phenolic compounds in prunes had been found to inhibit human LDL oxidation in vitro, and thus might serve as preventive agents against chronic diseases, such as heart disease and cancer. Additionally, high potassium content of prunes (745 mg/100 g) might be beneficial for cardiovascular health. Dried prunes are an important source of boron, which is postulated to play a role in prevention of osteoporosis. A serving of prunes (100 g) fulfills the daily requirement for boron (2 to 3 mg). More research is needed to assess the levels of carotenoids and other phytochemicals present in prunes to ensure correct labeling and accuracy of food composition tables in order to support dietary recommendations or health claims.

J Womens Health Gend Based Med. 2002 Jan-Feb;11(1):61-8.  

    Dried plums improve indices of bone formation in postmenopausal women.

    Arjmandi BH, Khalil DA, Lucas EA, Georgis A, Stoecker BJ, Hardin C, Payton ME, Wild RA.

    Department of Nutritional Sciences, Oklahoma State University, Stillwater, Oklahoma 74078-6141, USA.

    Menopause drastically increases the risk of osteoporosis. Aside from drug therapy, lifestyle and nutritional factors play an important role in the maintenance of skeletal health. Our recent findings suggest that dried plums, a rich source of phenolic and flavonoid compounds, are highly effective in modulating bone mass in an ovarian hormone-deficient rat model of osteoporosis. The objective of this study was to examine whether the addition of dried plums to the diets of postmenopausal women positively influences markers of bone turnover. Fifty-eight postmenopausal women not on hormone replacement therapy (HRT) were randomly assigned to consume either 100 g dried plums or 75 g dried apples daily for 3 months. Both dried fruit regimens provided similar amount of calories, fat, carbohydrate, and fiber. Serum and urinary biochemical markers of bone status were assessed before and after treatment. In comparison with corresponding baseline values, only dried plums significantly increased serum levels of insulin-like growth factor-I (IGF-I) and bone-specific alkaline phosphatase (BSAP) activity. Higher levels of both serum IGF-I and BSAP are associated with greater rates of bone formation. Serum and urinary markers of bone resorption, however, were not affected by either dietary regimen. The results of this study suggest that dried plums may exert positive effects on bone in postmenopausal women. Longer duration studies are needed to confirm the beneficial effects of dried plum on bone mineral density (BMD) and the skeletal health of postmenopausal women.

 

Menopause. 2005 Nov-Dec;12(6):755-62. Epub 2005 Nov 8.  

    Dried plum reverses bone loss in an osteopenic rat model of osteoporosis.

    Deyhim F, Stoecker BJ, Brusewitz GH, Devareddy L, Arjmandi BH.

    Department of Nutritional Sciences, 301 Human Environmental Sciences, Oklahoma State University, Stillwater, 74078-6141, USA.

    OBJECTIVE: We previously reported the efficacy of dried plum (Prunus domestica L.) in preventing ovariectomy-induced bone loss in a rat model of osteoporosis and improving bone biomarkers in postmenopausal women. The present study evaluated whether dried plum was able to restore bone mass in osteopenic ovariectomized rats. DESIGN: Ninety-day-old Sprague-Dawley rats were either sham-operated (Sham; one group) or ovariectomized (Ovx; five groups) and were fed a standard diet for 40 days to establish bone loss and subsequently experimental treatments were initiated. Sham, Ovx control, and Ovx + 17beta-estradiol (E2; 10 microg/kg body weight per day) animals continued to receive the standard diet, whereas the remaining three Ovx groups received the following dietary treatments: Ovx + 5% dried plum (low dose), Ovx + 15% dried plum (medium dose), and Ovx + 25% dried plum (high dose). After 60 days, blood and bone specimens were collected for analyses. RESULTS: Dried plum, as low as 5%, was effective in restoring femoral and tibial bone density. Dried plum increased lumbar bone density as well, with HD achieving a statistical significance. The increase in femoral bone density of dried plum-fed rats resulted in improved bone quality as indicated by 6.9% and 6.0% improvement in overall yield and ultimate force, respectively. Varying doses of dried plum were also able to significantly improve trabecular microarchitectural properties in comparison with ovariectomized controls. CONCLUSIONS: The improvement in biomechanical properties of long bones due to dried plum, in part, may be due to the favorable microstructural changes as evident by enhanced tibial bone volume and connectivity. Loss of bone volume accompanied by loss of trabecular connectivity is generally believed to be an irreversible process, but our observations suggest that dried plum improves trabecular microstructure of tibia after losses have already occurred.

 

Bone. 2006 Dec;39(6):1331-42. Epub 2006 Aug 4.  

    Dried plum prevents bone loss in a male osteoporosis model via IGF-I and the RANK pathway.

    Franklin M, Bu SY, Lerner MR, Lancaster EA, Bellmer D, Marlow D, Lightfoot SA, Arjmandi BH, Brackett DJ, Lucas EA, Smith BJ.

    Department of Nutritional Sciences, College of Human Environmental Science, Oklahoma State University, Stillwater, OK 74078, USA.

    Previously, dietary supplementation with dried plums, a rich source of polyphenolic compounds with antioxidant and anti-inflammatory properties, has been shown to improve bone density, microstructure and biomechanics in female animal models of osteopenia. We designed this study to determine the extent to which dried plum prevents skeletal deterioration in gonadal hormone deficient male animals and to begin to understand its mechanism of action. Sixty 6-month-old male Sprague-Dawley rats were either sham-operated (Sham = 1 group) or orchidectomized (ORX = 4 groups) and randomly assigned to dietary treatments: standard semi-purified diet (Control) with either LD = 5%, MD = 15%, or HD = 25% (w/w) dried plum for 90 days. At the end of the treatment period, both the MD and HD dried plum completely prevented the ORX-induced decrease in whole body, femur, and lumbar vertebra bone mineral density (BMD). Biomechanical testing indicated that the MD and HD of dried plum prevented the ORX-induced decrease in ultimate load of the cortical bone as well as the compressive force and stiffness of trabecular bone within the vertebrae. Analyses of trabecular microarchitecture of the distal femur metaphysis and vertebral body revealed that HD dried plum protected against the decrease in trabecular bone volume (BV/TV) induced by ORX. In the distal femur, all doses of dried plum improved trabecular number (TbN) and separation (TbSp) compared to the ORX-control group, while MD and HD dried plum prevented the ORX-induced changes in vertebral TbN and TbSp. At the end of the 90-day treatment, no remarkable changes in serum osteocalcin or alkaline phosphatase in any of the treatment groups were observed, while serum insulin-like growth factor (IGF)-I was increased by dried plum. The ORX-induced increase in urinary deoxypyridinoline (DPD) excretion was completely prevented by all doses of dried plum coinciding with down-regulation of gene expression for receptor activator of NFkappa-B ligand (RANKL) and osteoprotegerin (OPG) in the bone. We conclude that dried plum prevents osteopenia in androgen deficient male rats, and these beneficial effects may be attributed in part to a decrease in osteoclastogenesis via down-regulation of RANKL and stimulation of bone formation mediated by IGF-I.

Osteoporos Int. 2007 Jul;18(7):931-42. Epub 2007 Feb 15.  

    Comparison of dried plum supplementation and intermittent PTH in restoring bone in osteopenic orchidectomized rats.

    Bu SY, Lucas EA, Franklin M, Marlow D, Brackett DJ, Boldrin EA, Devareddy L, Arjmandi BH, Smith BJ.

    Department of Nutritional Sciences, College of Human Environmental Science, Oklahoma State University, Stillwater, OK 74078, USA.

    SUMMARY: Bone loss was confirmed after 90 days in 50 6-month-old male Sprague Dawley rats that were sham-operated or orchidectomized (ORX). In this study, we have shown that dried plum (DP) has potent effects on bone in terms of bone mass, microarchitecture, and strength in osteopenic male rats. Although these changes may be mediated through the suppression of bone resorption, the fact that the restoration in some of the bone structural and biomechanical parameter shares some similarities with parathyroid hormone (PTH) should not be overlooked. Further investigation is needed on a mechanistic level to clarify the influence of DP on bone metabolism. INTRODUCTION: This study was designed to investigate the extent to which DP reverses bone loss in osteopenic ORX rats and to compare its effects to PTH. MATERIALS AND METHODS: Fifty, 6-month-old male Sprague Dawley rats were sham-operated or ORX, and bone loss was confirmed after 90 days. The ORX groups were assigned to control (AIN-93M) diet, 25% DP diet, or PTH (80 microg/kg) for 90 days. RESULTS: DP induced an 11% increase in vertebral and femoral BMD compared to ORX-controls. BMD in the PTH-treated group was increased by 20.7% (vertebra) and 17.9% (femur). Vertebral trabecular bone volume (BV/TV) and number were increased by DP and trabecular separation was decreased compared to controls, which were similar to PTH. Alterations in trabecular bone of the femur were similar to those in the vertebra, but DP did not restore BV/TV to the same extent. Cortical thickness was improved by DP and further enhanced by PTH. DP tended to decrease urinary deoxypyridinoline and calcium, but did not alter alkaline phosphatase or osteocalcin. CONCLUSION: We conclude that though the degree of improvement was not equivalent to PTH with regard to all parameters, DP reverses bone loss due to ORX and the mechanisms should be further investigated.

 

J Nutr Biochem. 2008 May 19. [Epub ahead of print]  

    Dried plum polyphenols attenuate the detrimental effects of TNF-alpha on osteoblast function coincident with up-regulation of Runx2, Osterix and IGF-I.

    Bu SY, Hunt TS, Smith BJ.

    Department of Nutritional Sciences, College of Human Environmental Science, Oklahoma State University, Stillwater, OK 74078.

    Previous studies have demonstrated that dried plums which contain high amounts of polyphenols can restore bone mass and structure, and significantly increase indices of bone formation. The purpose of this study was to determine how dried plum polyphenols influence osteoblast activity and mineralized nodule formation under normal and inflammatory conditions. MC3T3-E1 cells were plated and pretreated with dried plum polyphenols (0, 2.5, 5, 10 and 20 mug/ml) and 24 h later stimulated with TNF-alpha (0 or 1.0 ng/ml). The 5, 10 and 20 mug/ml doses of polyphenols significantly increased intracellular ALP activity under normal conditions at 7 and 14 days, and restored the TNF-alpha-induced suppression of intracellular ALP activity by 14 days (P<.001). Polyphenols also increased mineralized nodule formation under normal and inflammatory conditions. In the absence of TNF-alpha, 5 mug/ml of polyphenols significantly up-regulated the growth factor, IGF-I, compared to controls, and the 5 and 10 mug/ml doses increased the expression of lysyl oxidase involved in collagen crosslinking. TNF-alpha decreased the expression of Runx2, Osterix and IGF-I, and polyphenols restored their mRNA levels to that of the controls. Although TNF-alpha failed to alter lysyl oxidase at 18 h, the polyphenols up-regulated its expression (P<.05) in the presence of TNF-alpha. As expected, TNF-alpha up-regulated RANKL mRNA and polyphenols suppressed RANKL expression without altering OPG. Based on these findings, we conclude that dried plum polyphenols enhance osteoblast activity and function by up-regulating Runx2, Osterix and IGF-I and increasing lysyl oxidase expression, and at the same time attenuate osteoclastogenesis signaling.

Calcif Tissue Int. 2008 May 29. [Epub ahead of print]  

    Dried Plum Polyphenols Inhibit Osteoclastogenesis by Downregulating NFATc1 and Inflammatory Mediators.

    Bu SY, Lerner M, Stoecker BJ, Boldrin E, Brackett DJ, Lucas EA, Smith BJ.

    Department of Nutritional Sciences, College of Human Environmental Sciences, Oklahoma State University, Stillwater, OK, 74078, USA.

    Dried plums and their polyphenols have been shown to suppress bone resorption by downregulating receptor activator NF-kappaB ligand (RANKL). Due to the anti-inflammatory and antioxidant properties of these compounds, this study was designed to investigate whether dried plum polyphenols exert additional, more direct effects on osteoclasts and their precursors. RAW 264.7 macrophages were used as a model to study osteoclast precursors and osteoclast differentiation and activity. Under inflammatory conditions induced by lipopolysaccharide (LPS), polyphenols extracted from dried plum (10, 20, and 30 mug/mL) downregulated osteoclast precursor cyclooxygenase expression and nitric oxide (NO) by inhibiting inducible NO synthase. NO and tumor necrosis factor (TNF)-alpha were also suppressed in the presence of RANKL during osteoclastogenesis by the polyphenols. Increased TNF-alpha production in response to oxidative stress, but not LPS, was decreased over time. As expected, LPS and H(2)O(2 )significantly increased the number of tartrate-resistant acid phosphatase-positive cells by 127% and 30%, respectively. Dried plum polyphenols decreased osteoclast differentiation under normal as well as inflammatory and oxidative stress conditions, coincident with the suppression of the transcription factor, nuclear factor for activated T cells (NFATc1). These inhibitory effects on osteoclastogenesis were confirmed in primary bone marrow cultures. Resorption pit formation was decreased to a similar extent as osteoclast differentiation, suggesting that dried plum polyphenols primarily affect osteoclast differentiation as opposed to activity. Our data demonstrate that dried plum polyphenols directly inhibit osteoclastogenesis, leading to a decrease in osteoclast activity, by downregulating NFATc1 and inflammatory mediators.