A study published in last September’s British Journal of Nutrition has moved the “Prune Diet” from something we thought might work into the category of something that looks like it does work.
Hooshmand et al describe the results of a clinical trial began in 2007 by Bharam Arjmandi. A group of 160 postmenopausal women were split into two groups. One groups ate dried plums each day while a second group ate dried apples each day and acted as the control. All the women took calcium (500 mg/day) and vitamin D (400 IU/day).
Bone mineral density was measured at the start of the study and at 3, 6 and 12 months.
Thos women who ate dried plums had significantly increased bone mineral density of ulna and spine in comparison with those who ate dried apples. Those eating the dried plums also had significantly decreased serum levels of bone turnover markers including bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase-5b (this is a good thing to see). 
The idea that prunes could be used to treat osteoporosis isn’t new. This study just confirms what earlier studies had already been telling us,
that consumption of dried plums improved bone mineral density (BMD) by suppressing rate of bone turnover. Daily consumption of prunes should now be considered a valid strategy for prevention and treatment of osteoporosis.
Many women we see are quite hesitant to take the bisphosphonate drugs prescribed for osteoporosis. There are good reasons that they do. The big story is the growing evidence that links these drugs with osteonecrosis of the jaw, what is commonly called ‘dead jaw syndrome.’ Then there are the more recent indications that long term use actually increases risk of femur fractures.
[NOTE: Dried plums are the same thing as prunes. The dried plum term might be considered a euphemism employed to rebrand this long time staple food in order to increase sales. The official name change happened in 2000, so now under Food and Drug Administration (FDA) rules prunes are officially ‘dried plums.’]
Bahram Arjmandi who is listed as a coauthor on the September’s paper, has been investigating dried plums for over a decade; his first paper was published in 2001. 
In fact the current report is almost identical to a pilot study Arjmandi published in 2002. Arjmandi had previously shown that dried plums were, “ … highly effective in modulating bone mass in an ovarian hormone-deficient rat model of osteoporosis…..” So, Arjmandi conducted a 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 were randomly assigned to eat either 100 grams of dried plums or 75 grams of dried apples every day. 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. The drugs typically used to treat osteoporosis focus on the other side of the equation; they slow bone resorption.
Since then Arjmandi has written a string of papers using animal models of osteoporosis in order to better understand the action dried plums have on bone. In a 2005 paper using ovariectomized rats, he reported that, “Dried plum, ….[restored] femoral and tibial bone density…. increased lumbar bone density as well, ….. improved bone quality …. [and] improve[d] trabecular microarchitectural properties in comparison with ovariectomized controls.”
Arjmandi pointed out the unique action dried plums had on bone:
“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.” 
Similar benefits were obtained using castrated male rats and reported in 2006: “…. dried plum completely prevented the … [castration induced] decrease in whole body, femur, and lumbar vertebra bone mineral density (BMD).” The bone resorption biomarker deoxypyridinoline (DPD) rose by 36% in the castrated rats but dropped 57% in those rats consuming dried plums. 
In 2007, another rat study found that while dried plums were effective, parathyroid hormone was even more effective at restoring bone mass. 
Arjjmandi began this clinical trial under review when he moved Florida State University in 2007.
Several additional papers of interest have been published while this trial was underway. A 2008 paper explained that, “Dried plum polyphenols inhibit osteoclastogenesis by downregulating NFATc1 and inflammatory mediators.” 
A 2009 publication tells us that the polyphenols in dried plums “…..attenuate the detrimental effects of TNF-alpha on osteoblast function…” 
Of particular interest is a 2010 paper reporting that a combining dried plum and fructo-oligo-saccharide (FOS) supplements increased both of their bone restoring effects. In fact this combination had a greater effect at increasing bone density than any other functional foods yet tested.  Also of note, there is an additional mouse study published in 2010, showing that dried plum supplements could restore lost bone mass in aged mice. 
Although this current study leaves little doubt that eating dried plums preserves bone, the question then is whether patients can actually be eat enough of these things? The daily dose of dried plums used in this experiment was 100 grams, that’s equivalent to about a dozen prunes. For a lot of people that many prunes will have a laxative effect. Knowing what to do and doing it may prove to be two different matters. One way to approach this is to simply take prunes, “to bowel tolerance.” That means eat as many as you can comfortably. Over time you can increase the dose as your body learns to tolerate move over time.
Another option is to combine the prunes with other things or foods that have the opposite effect on bowel transit times (BTT), things that tend to be constipating. Calcium certainly does this to many people. So do ground poppy seeds and carob powder. It is perhaps noteworthy that both ground poppy seed and prune paste have been traditionally consumed in close proximity in certain cultures. Keep this in mind if your prune tolerance is low.
Fortuitously, a fair percentage of patients who are in the age that they may benefit from “prune therapy” also have relatively slow BTT (that’s the fancy way to say they are constipated) and this prune prescription may provide relief.
1. Hooshmand S, Chai SC, Saadat RL, Payton ME, Brummel-Smith K, Arjmandi BH. Comparative effects of dried plum and dried apple on bone in postmenopausal women. Br J Nutr. 2011 Sep;106(6):923-30.
2. Sharma V, Nagaraj S, Choksey U, Hegde A, Samant R, Balakrishnan C. Bisphosphonate-induced osteonecrosis of the jaw. J Assoc Physicians India. 2011 Aug;59:516-7.
3. Arjmandi BH. The role of phytoestrogens in the prevention and treatment of osteoporosis in ovarian hormone deficiency. J Am Coll Nutr. 2001 Oct;20(5 Suppl):398S-402S; discussion 417S-420S.
4. Deyhim F, Stoecker BJ, Brusewitz GH, Devareddy L, Arjmandi BH. Dried plum reverses bone loss in an osteopenic rat model of osteoporosis. Menopause. 2005 Nov-Dec;12(6):755-62.
5. Franklin M, Bu SY, Lerner MR, Lancaster EA, Bellmer D, Marlow D, et al. Dried plum prevents bone loss in a male osteoporosis model via IGF-I and the RANK pathway. Bone. 2006 Dec;39(6):1331-42.
6. Bu SY, Lucas EA, Franklin M, Marlow D, Brackett DJ, Boldrin EA, et al. Comparison of dried plum supplementation and intermittent PTH in restoring bone in osteopenic orchidectomized rats. Osteoporos Int. 2007 Jul;18(7):931-42
7. Bu SY, Lerner M, Stoecker BJ, Boldrin E, Brackett DJ, Lucas EA, et al. Dried plum polyphenols inhibit osteoclastogenesis by downregulating NFATc1 and inflammatory mediators. Calcif Tissue Int. 2008 Jun;82(6):475-88.
8. Bu SY, Hunt TS, Smith BJ. Dried plum polyphenols attenuate the detrimental effects of TNF-alpha on osteoblast function coincident with up-regulation of Runx2, Osterix and IGF-I. J Nutr Biochem. 2009 Jan;20(1):35-44.
9. Arjmandi BH, Johnson CD, Campbell SC, Hooshmand S, Chai SC, Akhter MP. Combining fructooligosaccharide and dried plum has the greatest effect on restoring bone mineral density among select functional foods and bioactive compounds. J Med Food. 2010 Apr;13(2):312-9.
10. Halloran BP, Wronski TJ, VonHerzen DC, Chu V, Xia X, Pingel JE, et al. Dietary dried plum increases bone mass in adult and aged male mice. J Nutr. 2010 Oct;140(10):1781-7.