Friday, January 27, 2017

New Data on the Benefits of Prunes

This is an update of a column I wrote in 2015, with some new data on the osteoporosis benefits of prunes. Prunes are now called dried plums by some nutritionists and prune makers, because of their negative image as a medicinal food for the elderly.  Don’t be put off – read on!

Osteoporosis – Studies form Florida State University, published in the British Journal of Nutrition, showed that in rats subjected to treatments that produced osteoporosis, prunes in the diet were able to reverse bone loss.  In a human study, a group of post-menopausal women was given 100 grams of prunes per day (about 10 prunes) and a comparison group was told to consume 100 grams of dried apples.  After 12 months, the group eating the prunes had significantly higher bone mineral density in the ulna (an arm bone) and spine.  Authors of the study said that prunes are able to suppress bone breakdown, which tends to exceed new bone growth as people age.  This effect may be due to good levels of the mineral boron in prunes.  Other foods high in boron are plums, grapes, avocados, almonds and peanuts.  

A recent study from the Texas A&M Research center showed that prunes protect against the bone loss caused by ionizing radiation.  UC Irvine and UC San Francisco also participated in this research. The study, done in mice, showed that consuming prunes can protect from ionizing radiation that increases oxidative damage in skeletal tissues and results in an imbalance in bone remodeling. "Bone loss caused by ionizing radiation is a potential health concern for those in occupations or in situations that expose them to radiation," the study said. "This is relevant to not only astronauts in space, but also cancer patients, those undergoing radiotherapy, radiation workers and victims of nuclear accidents."

The team investigated interventions they thought might prevent bone damage and oxidative stress-related factors leading to cancellous bone loss, also known as "spongy bone," from exposure to both low linear energy transfer and high linear energy transfer radiation. They evaluated different interventions with antioxidant or anti-inflammatory properties, including an antioxidant cocktail, dihydrolipoic acid, ibuprofen and prunes, to determine their ability to prevent bone loss and to blunt the expression of genes in marrow cells that lead to the breakdown of bone. They found that prunes "contain biologically active components that may provide effective interventions for loss of structural integrity caused by radiotherapy or unavoidable exposure to space radiation incurred over long-duration spaceflight.” They noted that prunes contain various bioactive compounds, including polyphenols that are known for their high antioxidant and anti-inflammatory properties.

Laxative Effect – Prunes are well known for their ability to help with constipation.  They are a safe laxative for most people. This is due to their fiber and high sorbitol content, which retains fluid in the intestines.  Sorbitol is a natural sugar found in many fruits.  It is metabolized relatively slowly, so that prunes do not cause a rapid rise in blood sugar.  Many people with diabetes can eat them in moderation (but check with your health care provider). 

Colon Cancer – Research from Texas A&M University and the University of North Carolina has shown that prunes can positively affect gut bacteria (the microbiome) and help to reduce the risk of colon cancer. There are trillions of bacteria in the intestinal tract – more than 400 individual species have been identified.  Disruptions to the microbiome are involved in intestinal inflammation, which can promote the development of colon cancer. Prunes contain antioxidant compounds that can neutralize free radicals that damage DNA.  In a rat study on colon cancer antecedents, rats fed with prunes (and their regular chow) showed significantly reduced numbers of precancerous changes in the intestinal walls compared to a control group.

Weight Loss – Research by the University of Liverpool found that eating prunes as part of a weight loss diet helped in weight control.  100 overweight or obese men and women were tested for 12 weeks.  Half the subjects were given about 14 prunes per day along with their diet, and the other half got advice on healthy snacks.  The group that ate prunes lost 4.4 pounds and an inch from their waist.  The control group lost 3.5 pounds and .7 inches from the waist.  Also, the group eating prunes experienced greater feelings of fullness during the weight loss diet.  The diets were matched for calories.

Some people don’t like the taste of prunes, and may need to disguise them in shakes and stir-fries. If you have colon cancer in your family; if your diet is high in red or processed meat; if you have osteoporosis in your family, if you have low bone density yourself, or if you are a budding astronaut, you may want to give prunes a chance. 
           Sadja Greenwood, MD  Back issues at


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