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Prunes and Evidence Based Medicine

March 26, 2011

DNC News

Our dog Poppy was named after a poppy seed filled hamantashen. Up until she was about twelve weeks old, we had been calling her ‘puppy’. It was Purim, the Jewish holiday that celebrates how Queen Esther saved the Jewish people and as part of the celebration we make pastries filled with either poppy seeds or prunes.

How far back this culinary tradition goes is unclear. The holiday has been celebrated for nearly two millennium. As both opium cultivation and the drying of plums to make prunes both originated in the general area in which the Purim story occurred, one could assume the custom of eating hamantashen in association with the holiday goes back a very long time.

Poppy seeds, even those used to bake with, share a characteristic common to all poppy plant derivatives including opium and heroine. They cause constipation. Luckily the calculated consumption of prune filled hamantashen solves the problem of eating an excess of poppy seed versions. Prunes, as we are all well aware, have a laxative action. With ease, one can achieve a balance between the poppy and the prunes’ therapeutic actions.

Back to the story of our dog’s name. Six years ago, during the feast of Purim, as we sat around the dinner table consuming a last plate of home made hamantashen, my dear wife lifted the last fragment of poppy seed filled hamantashen into the air and declared, “I love poppy.” Our young dog, up to then who had only been referred to as ‘puppy’, assumed Rena was talking about her and came bounding over.

This memory came back to me as I was reading a soon to be published study about prunes. We may all know what eating too many prunes will do but, in truth, this is only anecdotal evidence and until recently an unproven fact. We live in the age of what is called Evidence Based Medicine (EBM) and according to the rules we had no way to know whether the laxative effect attributed to prunes was real or merely a placebo effect. That worry is over.

A paper written by researchers from the University of Iowa College of Medicine will be published next month, April 2011, which will tell us that prunes really do help constipation.

The researchers fed 40 constipated test subjects either prunes or psyllium powder daily for 3 weeks in amounts that supplied 6 grams per day of fiber. After three weeks the subjects took a week off and then switched therapies. During the course of the experiment, the subjects kept careful diaries tracking all sorts of details about bowel habits that we don’t really need to discuss here. Suffice to say that when the data were collated and analyzed it was abundantly clear that prunes had a significant effect, doing what we all know they do.

This was not a perfect study by any means. It was only a single blinded placebo controlled trial, not the hallmark double-blinded trial that modern medicine considers the gold standard. There were only 40 subjects, 37 of whom were female. One might still argue that this study is insufficient evidence to base clinical decisions upon. Still it may be the first study that clearly demonstrates that prunes do what everyone has known they do since the Book of Esther was written in the second century.

This seems to point out the weakness of our current reliance on Evidence Based Medicine (EBM). If we adhere faithfully to the tenets of EBM, we would be obligated to suggest sodium docusate to relieve constipation, a substance that the drug manufacturers have proven works. Or if we insist on a more natural approach, we might consider psyllium, a fiber that research suggests may work better than sodium docusate. Up until now, prunes were not evidence based medicine; they were just food. Now we can say they work better than either of the other two therapies, at least in women.

When we are dealing with serious pharmaceutical agents it is nice to have evidence that they are beneficial. That’s because they often come with unwanted side effects. It’s nice to know that they will do what they promise. Perhaps we don’t need to require the same degree of caution with simple food therapies such as prunes. And especially with things that have so obvious and well-acknowledged action, we may not need double blinded placebo controlled randomized trials.

Advocates of evidence based medicine may certainly argue that our use of this example of prunes is inappropriate. An even more blatant example suggesting that EBM doesn't do well when faced with the obvious was published in the British Medical Journal in 2003. With tongues fully positioned in their cheeks, Gordon Smith and Jill Pell conducted a literature review seeking clinical trials, which evaluated whether parachutes were useful at gravity induced injury prevention, and found none.

Joking aside, there are few advocates of EBM that expect us to guide all clinical decisions based solely on published evidence and refrain from using common sense. Writing in 1996, Sackett et al, defined EBM as,

“… conscientious, explicit and judicious use of current best evidence in making decisions about care of individual patients…. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. By individual clinical expertise we mean the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice.”

EBM means integrating the science with clinical experience. While eating too many prunes has provided ‘clinical experience’ to many, it is reassuring that the evidence is finally catching up.

Related articles:

Prunes and Osteoporosis Link

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Attaluri A, Donahoe R, Valestin J, Brown K, Rao SS. Randomised clinical trial: dried plums (prunes) vs. psyllium for constipation. Aliment Pharmacol Ther. 2011 Apr;33(7):822-8.

McRorie JW, Daggy BP, Morel JG, Diersing PS, Miner PB, Robinson M. Psyllium is superior to docusate sodium for treatment of chronic constipation. Aliment Pharmacol Ther. 1998 May;12(5):491-7.

Smith GC, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials BMJ 327 : 1459 (18 December 2003)

Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn't. BMJ. 1996;312 (7023):71–2.