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The Forgotten Superfruit

November 10, 2009 Written by JP       [Font too small?]

It’s interesting how certain aspects of the past are glamorized while others are considered “dated”. We can easily find examples in the worlds of architecture, fashion, slang/speech and transportation. The same is true of the history of nutrition. Particular foods and beverages, such as a midday tea or a bowl of stewed prunes, are generally associated with a period that’s time has long passed.

A scientific review from 2001 attempted to re-popularize a food that had become associated almost exclusively with constipation in the elderly. The term “dried plum” was used to replace the antiquated word “prune”. We can debate whether or not a shift in public perception has occurred over the past 8 years. But what’s no longer controversial are the facts laid out in that summary produced in the Department of Human Nutrition and Dietetics at the University of Illinois, Chicago. The authors of that paper discuss the most obvious use of dried plums – a natural laxative. However, they go on to point out that these dehydrated fruits are also abundant sources of antioxidants, nutrients and phytochemicals that may assist in the management of cancer, diabetes, heart disease and osteoporosis. (1)

The issue of dried plums and bone health has received the most attention over the last decade or so. A scientific analysis from April 2009 evaluated the current status of that research. Scientists from Florida State University describe prunes as “the most effective fruit in both preventing and reversing bone loss”. They point out that dried plum extracts have been clinically proven in multiple animal studies and even a preliminary human trial. Here’s some of the evidence that they used to come to this conclusion: (2)

  • 58 postmenopausal women, who were not undergoing hormone replacement therapy, were given a daily dose of either 100 grams of dried plums or 75 grams of dried apples over the course of 3 months. Blood tests were taken prior to the intervention period and directly afterward. The results indicate that those receiving the prunes showed “significantly increased serum levels of insulin-like growth factor-I (IGF-I) and bone-specific alkaline phosphatase (BSAP)”. The authors go on to say that higher levels of IGF-I and BSAP are connected with “greater rates of bone formation”. (3)
  • A variety of animal experiments provide a strong rationale for using dried plums in the management of bone loss. Several explanations have emerged as to how prunes appear to assist the skeletal system: a) by providing an anti-inflammatory effect that decreases the number of cells (osteoclasts) that contribute to the destruction of bone; b) by enhancing the activity and function of cells that build bone (osteoblasts); c) by counteracting bone loss resulting from age-related hormonal changes in male and female (test animals); d) by providing a rich source of the trace mineral boron and Vitamin K, both of which are considered essential in promoting skeletal integrity. (4,5,6,7,8,9,10,11)

Many fruits aren’t appropriate for those with serious blood sugar disorders or individuals who are on carbohydrate restricted diets. One of the more interesting aspects of prunes is that they may have a positive impact on blood sugar levels and serum insulin concentrations. A Japanese study from 2005 found that diabetic rats fed plum juice actually showed improvements in blood sugar and insulin levels. The researchers also noted increased adiponectin concentrations in the fatty tissue of the rats. Adiponectin is a hormone that positively affects blood glucose and lipid levels and may thereby reduce the risk of cardiovascular disease and diabetes. It’s also important to note that the carbohydrates in prunes are largely comprised of a sugar alcohol (sorbitol) which tends to have a milder impact on blood sugar. This unique carbohydrate composition is reflected in the low glycemic index and glycemic load of prunes. For instance, prunes are classified as having a glycemic index or 29 and glycemic load of 10. Another similar dried fruit, raisins, have a glycemic index of 64 and a glycemic load of 28. For those who wish to avoid the carbohydrates altogether, there are select nutritional supplements that provide sugar-free plum extracts. (12,13,14,15)

Apart from helping to manage blood sugar, dried plums may also benefit the cardiovascular system in an even more direct manner. A recent study in the British Journal of Nutrition tested the effects of prunes in a group of mice that were genetically prone to heart disease. The test animals were divided into three sections: a) received a high cholesterol diet; b) the same diet + 4.75% dried plum; c) diet + 9.5% dried plum for 5 months. An additional group was fed a cholesterol-free diet as a further means of comparison (a “negative control”). Blood tests and internal examinations (of arteries) were conducted pre and post trial. Lower levels of inflammation, oxidative stress, triglycerides and fewer “artherosclerotic lesion areas” (arterial plaque) were found in the mice receiving the plum supplemented diets. Previous studies in both animals and humans have demonstrated that diets supplemented with prunes and prune fiber are capable of lowering cholesterol levels. (16,17,18)

There’s even encouraging news on the cancer front. A test tube study from 2006 established a prune extract as a viable tool in promoting the death of colon cancer cells and suppressing the spread of existing malignant cells. A 2005 investigation from the Department of Food Science and Nutrition at the University of Minnesota, St. Paul examined the potential of prunes in the prevention of colon cancer in an animal model. The results of that experiment indicate that prunes “greatly increased” antioxidant activity in the test rats and may effectively reduce the risk of certain colon cancer risk factors. (19,20)

Source: USDA Human Nutrition Research Center on Aging (link)

Although most of the research about dried plums is encouraging, there’s still much that needs to learned. In the May 2009 edition of the journal Nutrition, a study compared the effects of a dried plum extract vs. plum juice in a group of older rats with memory problems. The rats that received the juice but not the dried extract exhibited improvements in “working memory”. The authors of the study postulated that differences in the amount of specific antioxidants (phenolics) may be responsible for this unexpected outcome. These findings were surprising because previous data suggests that dried plums tend to have higher levels of phenolics than fresh plums. However, like all other natural foods, plums contain other antioxidants and phytochemicals that could be involved in this reported outcome. (21,22,23,24,25)

The future of prune research also appears to be rather promising. Food scientists are currently looking into the possibility of adding small amounts (3%) of dried plums into meat products such as pork sausage in order to extend shelf life and improve nutritional content. Combinations of foods such as dried plum + soy + fructooligosaccharides (prebiotics) are also being tested to determine whether they have a synergistic effect in combating bone loss. Thus far, one study suggests that adding all three of these foods together may be more effective than applying them individually. I’m certainly interested in seeing what comes next for this decidedly un-glamorous fruit. It doesn’t much matter what it’s called, dried plum or prune. What’s important is that we don’t relegate this valuable food to staying a relic of the past. (26,27)

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

Be well!

JP

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Posted in Bone and Joint Health, Food and Drink, Women's Health

17 Comments & Updates to “The Forgotten Superfruit”

  1. Nina K. Says:

    Wow, prunes are good against bone loss? i eat them often as a little snack, but not more than 2 of them and to of dried apricots. more is not good for bowel ;-)

    i try to keep my carb intake low and thought it wouldn’t be good to eat dried fruits because of the sugar. but i have the impression that sugar from fruits maybe is not that bad like starch from cereals etc…

    greetings
    Nina K.

  2. JP Says:

    Nina,

    It’s true! :)

    In the case of prunes, I think your sugar observation is correct. The reason for this is not likely just the carbohydrate composition. It also appears that certain phytochemicals in this dried fruit may moderate the digestion of the natural sugars present. Add to that the high fiber content and it appears that these fruits may be more appropriate for those with blood sugar issues than most. There’s also that “self limiting” laxative aspect of prune eating that tends to prevent overconsumption. ;)

    Be well!

    JP

  3. anne h Says:

    Like a binge on nuts, “self-limiting” is the key word!!

  4. JP Says:

    Anne,

    True but prunes are more willing to remind you if you go overboard! ;)

    Be well!

    JP

  5. Angie Says:

    Plum in my sausage is fine by me!

  6. JP Says:

    Me too, Angie! :)

    Be well!

    JP

  7. Steve Knobler, LAc Says:

    True – plums are great for building body fluids and treating liver diseases and diabetes. One caution though…according to “Healing With Whole Foods”, an excellent resource by Paul Pitchford, “plums are not good for people with delicate digestion or gastrointestinal ulcers or inflammation. Rich in oxalic acid, plums can deplete calcium in the body”

    Steve Knobler, Licensed Acupuncturist
    North Seattle Community Acupuncture
    http://www.northseaforme.com

  8. JP Says:

    Thanks for adding that information, Steve. :)

    To the best of my knowledge, oxalates don’t chelate or deplete calcium. They can however decrease calcium absorption if consumed at the same time as calcium-rich foods and/or supplements. This effect is generally not considered a significant enough factor to have a major impact on calcium status however.

    I do agree that prunes may not agree with some people with sensitive digestive systems. There’s also a theoretical concern that oxalates, contained in foods such as prunes, may not be appropriate for those with certain types of kidney and gallstones. Under those specific circumstances, caution may be warranted.

    Be well!

    JP

  9. Jo Says:

    Very interesting! I tend to love dried figs, cranberries and apricots best. I will, however, make an effort to throw some prunes in the mix after reading this.

  10. JP Says:

    Thanks, Jo! :)

    I hope you enjoy them and that they serve you well!

    Be well!

    JP

  11. hoberthz Says:

    If somebody just can make me a definition on this please. I think I( got the idea but stiil I little confusued, since there are more than 40.000 of variaty of plums family. So in our territorial lenguage wich are the really ones more directly associated with the new study, Me and My Wife both we have osteoproblems. Sorry for the lack of knowleage.

  12. JP Says:

    Hoberthz,

    The variety of dried plum in question is Prunus domestica L.

    Be well!

    JP

  13. JP Says:

    An update from the scientific literature:

    http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9281940&fileId=S0007114514000671

    Br J Nutr. 2014 Jul;112(1):55-60. doi: 10.1017/S0007114514000671. Epub 2014 Apr 29.

    The effect of dried plum on serum levels of receptor activator of NF-κB ligand, osteoprotegerin and sclerostin in osteopenic postmenopausal women: a randomised controlled trial.

    Hooshmand S1, Brisco JR1, Arjmandi BH2.

    Although several studies have confirmed the bone-protective properties of dried plum, its exact mechanisms of action remain unclear. Recent research has shown that osteocytes may control bone formation via the production of sclerostin and bone resorption via the receptor activator of NF-κB ligand (RANKL) and its inhibitor osteoprotegerin (OPG). To investigate the mechanism of action of dried plum in reversing bone loss, we measured serum levels of RANKL, OPG and sclerostin in osteopenic postmenopausal women (n 160). Participants were randomly assigned to the treatment group of either 100 g dried plum/d or 75 g dried apple/d (comparative control) for 1 year. All participants received 500 mg Ca plus 400 IU (10 μg) vitamin D daily. Bone mineral densities (BMD) of the lumbar spine, forearm, hip and whole body were assessed at baseline and at the end of the study using dual-energy X-ray absorptiometry. Blood samples were collected at baseline and after 12 months to assess bone biomarkers. Dried plum significantly increased the BMD of the ulna and spine in comparison with the control group. In comparison with corresponding baseline values, dried plum increased the RANKL levels by only +1·99 v. +18·33 % and increased the OPG levels by +4·87 v. – 2·15 % in the control group. Serum sclerostin levels were reduced by – 1·12 % in the dried plum group v. +3·78 % in the control group. Although percentage changes did not reach statistical significance (P≤ 0·05), these preliminary data may indicate that the positive effects of dried plum on bone are in part due to the suppression of RANKL production, the promotion of OPG and the inhibition of sclerostin.

    Be well!

    JP

  14. JP Says:

    Updated 04/18/16:

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750446/

    Sci Rep. 2016 Feb 11;6:21343.

    Dried plum diet protects from bone loss caused by ionizing radiation.

    Bone loss caused by ionizing radiation is a potential health concern for radiotherapy patients, radiation workers and astronauts. In animal studies, exposure to ionizing radiation increases oxidative damage in skeletal tissues, and results in an imbalance in bone remodeling initiated by increased bone-resorbing osteoclasts. Therefore, we evaluated various candidate interventions with antioxidant or anti-inflammatory activities (antioxidant cocktail, dihydrolipoic acid, ibuprofen, dried plum) both for their ability to blunt the expression of resorption-related genes in marrow cells after irradiation with either gamma rays (photons, 2 Gy) or simulated space radiation (protons and heavy ions, 1 Gy) and to prevent bone loss. Dried plum was most effective in reducing the expression of genes related to bone resorption (Nfe2l2, Rankl, Mcp1, Opg, TNF-α) and also preventing later cancellous bone decrements caused by irradiation with either photons or heavy ions. Thus, dietary supplementation with DP may prevent the skeletal effects of radiation exposures either in space or on Earth.

    Be well!

    JP

  15. JP Says:

    Updated 04/18/16:

    http://link.springer.com/article/10.1007%2Fs00198-016-3524-8

    Osteoporos Int. 2016 Feb 22.

    The effect of two doses of dried plum on bone density and bone biomarkers in osteopenic postmenopausal women: a randomized, controlled trial.

    Daily consumption of 50 g of dried plum (equivalent to 5-6 dried plums) for 6 months may be as effective as 100 g of dried plum in preventing bone loss in older, osteopenic postmenopausal women. To some extent, these results may be attributed to the inhibition of bone resorption with the concurrent maintenance of bone formation.

    INTRODUCTION: The objective of our current study was to examine the possible dose-dependent effects of dried plum in preventing bone loss in older osteopenic postmenopausal women.

    METHODS: Forty-eight osteopenic women (65-79 years old) were randomly assigned into one of three treatment groups for 6 months: (1) 50 g of dried plum; (2) 100 g of dried plum; and (3) control. Total body, hip, and lumbar bone mineral density (BMD) were evaluated at baseline and 6 months using dual-energy X-ray absorptiometry. Blood biomarkers including bone-specific alkaline phosphatase (BAP), tartrate-resistant acid phosphatase (TRAP-5b), high-sensitivity C-reactive protein (hs-CRP), insulin-like growth factor-1 (IGF-1), and sclerostin were measured at baseline, 3 months, and 6 months. Osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), calcium, phosphorous, and vitamin D were measured at baseline and 6 months.

    RESULTS: Both doses of dried plum were able to prevent the loss of total body BMD compared with that of the control group (P < 0.05). TRAP-5b, a marker of bone resorption, decreased at 3 months and this was sustained at 6 months in both 50 and 100 g dried plum groups (P < 0.01 and P < 0.04, respectively). Although there were no significant changes in BAP for either of the dried plum groups, the BAP/TRAP-5b ratio was significantly (P < 0.05) greater at 6 months in both dried plum groups whereas there were no changes in the control group.

    CONCLUSIONS: These results confirm the ability of dried plum to prevent the loss of total body BMD in older osteopenic postmenopausal women and 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.

    Be well!

    JP

  16. JP Says:

    Updated 04/18/16:

    http://onlinelibrary.wiley.com/doi/10.1002/ptr.5581/abstract

    Phytother Res. 2016 Mar 16.

    A Systematic Review on the Health Effects of Plums (Prunus domestica and Prunus salicina).

    In recent times, plums have been described as foods with health-promoting properties. Research on the health effects of plum continue to show promising results on its antiinflammatory, antioxidant and memory-improving characteristics. The increased interest in plum research has been attributed to its high phenolic content, mostly the anthocyanins, which are known to be natural antioxidants. A systematic review of literature was carried out to summarize the available evidence on the impact of plums (Prunus species; domestica and salicina) on disease risk factors and health outcomes. A number of databases were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for relevant studies on plum health effects in vitro, animal studies and clinical trials. A total of 73 relevant peer-reviewed journal articles were included in this review. The level of evidence remains low. Of the 25 human studies, 6 were confirmatory studies of moderate quality, while 19 were exploratory. Plums have been shown to possess antioxidant and antiallergic properties, and consumption is associated with improved cognitive function, bone health parameters and cardiovascular risk factors. Most of the human trials used the dried version of plums rather than fresh fruit, thus limiting translation to dietary messages of the positioning of plums in a healthy diet. Evidence on the health effect of plums has not been extensively studied, and the available evidence needs further confirmation.

    Be well!

    JP

  17. JP Says:

    Updated 1/31/18:

    http://www.mdpi.com/2072-6643/9/4/401/htm

    Nutrients. 2017 Apr 19;9(4).

    Dried Plums, Prunes and Bone Health: A Comprehensive Review.

    The 2015-2020 Dietary Guidelines for Americans advocate for increasing fruit intake and replacing energy-dense foods with those that are nutrient-dense. Nutrition across the lifespan is pivotal for the healthy development and maintenance of bone. The National Osteoporosis Foundation estimates that over half of Americans age 50+ have either osteoporosis or low bone mass. Dried plums, also commonly referred to as prunes, have a unique nutrient and dietary bioactive profile and are suggested to exert beneficial effects on bone. To further elucidate and summarize the potential mechanisms and effects of dried plums on bone health, a comprehensive review of the scientific literature was conducted. The PubMed database was searched through 24 January 2017 for all cell, animal, population and clinical studies that examined the effects of dried plums and/or extracts of the former on markers of bone health. Twenty-four studies were included in the review and summarized in table form. The beneficial effects of dried plums on bone health may be in part due to the variety of phenolics present in the fruit. Animal and cell studies suggest that dried plums and/or their extracts enhance bone formation and inhibit bone resorption through their actions on cell signaling pathways that influence osteoblast and osteoclast differentiation. These studies are consistent with clinical studies that show that dried plums may exert beneficial effects on bone mineral density (BMD). Long-term prospective cohort studies using fractures and BMD as primary endpoints are needed to confirm the effects of smaller clinical, animal and mechanistic studies. Clinical and prospective cohort studies in men are also needed, since they represent roughly 29% of fractures, and likewise, diverse race and ethnic groups. No adverse effects were noted among any of the studies included in this comprehensive review. While the data are not completely consistent, this review suggests that postmenopausal women may safely consume dried plums as part of their fruit intake recommendations given their potential to have protective effects on bone loss.

    Be well!

    JP

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