Eating Prunes Can Reduce Inflammation and Improve Bone Health

In the 1970s the California Prune Advisory Board promoted its product as the “FUNNY FRUIT.” These days, prunes are advertised as dried plums. Researchers at Penn State investigated how eating prunes might bolster bone health after menopause (American Physiological Society (APS) annual meeting at Experimental Biology 2022). The idea that food could improve bone mineral density will likely surprise many health professionals.

Why Bone Health Is So Important!

Researchers point out (Contemporary Clinical Trials Communications, Aug. 2022):

“By 2030, the prevalence of osteoporosis for women 50 years and older is projected to reach 13.6 million and the prevalence of low bone mass is expected to reach 57.8 million. These estimates underscore the urgency for continued development and improvement of preventative strategies. Pharmacological therapies, such as estrogen therapy and bisphosphonates, are effective in the treatment of bone loss and osteoporosis, but have been declining in popularity due to undesirable side effects. Alternatively, consumer interest in non-pharmacological options for preventing and treating bone loss, particularly with dietary whole food supplementation, is on the rise.”

How Did Scientists Study the Benefits of Eating Prunes?

Researchers writing in the American Journal of Clinical Nutrition (Oct. 6, 2022) describe their “Prune Study” in postmenopausal women. This year-long study randomized 235 women to one of three groups.

The researchers discouraged women in the control group from eating prunes. The 50 gram group ate 50 grams of prunes daily, if the volunteers followed the protocol. That amounts to 4 to 6 prunes. The high-dose group consumed 100 grams of prunes daily. That was equal to 10 to 12 prunes.

The 50 gram dose of prunes increased bone mineral density within six months. To the researchers’ disappointment, the 100 gram dose of prunes led to a higher-than-expected dropout rate. As a result, the scientists could not compare the effectiveness of the high-dose prune regimen to controls or the 50 gram dose.

A Word About 100 Grams of Prunes Daily!

I don’t know about you, but I would find eating 10 to 12 prunes daily challenging! The protocol was:

“4 prunes after breakfast, 4 prunes after lunch and 4 prunes after dinner”

Here is how the scientists describe the drop-out rate:

“In the Control group, the dropout rate was 10% and the primary reason for dropout was time commitment. In the 50g Prune group, the dropout rate was 15% with the primary reasons for drop-out being poor tolerance to prunes and time commitment. In the 100g Prune group, the drop-out rate was 41% and significantly greater than the Control and 50g Prune groups (p<0.001), with the primary reasons for dropout was poor tolerance consuming the prunes, time commitment, or lost to follow up.”

The authors did not report why the high-dose prune eaters were more likely to drop out, but we suspect it might have had something to do with the digestive tract, ie, bloating, cramping, gas and/or diarrhea. Just a guess mind you, but a dozen prunes a day for a year might be a tad challenging for lots of people.

Why Would Eating Prunes Be Good for Bones?

The authors of the latest research provide some interesting background information.

“Prunes (i.e., dried plums) represent an attractive strategy since the phenolic compounds in prunes may mitigate postmenopausal bone loss mechanistically by exerting favorable effects on bone metabolism, and by targeting inflammatory signaling pathways that may modulate bone loss. Dietary supplementation with prunes has been shown to decrease bone resorption, and prevent or preserve bone.”

They conclude:

“The results of this investigation provide compelling evidence of the long-term efficacy of daily prune consumption. Given the high compliance and retention at the 50g dosage over 12 months, a moderate dosage of daily prune consumption represents a valuable non-pharmacological treatment strategy that can be used to preserve bone mass at the hip in postmenopausal females and possibly reduce the risk of hip fracture which is the primary goal for treatment of low BMD [bone mineral density]. This RCT [randomized controlled trial] represents the largest trial demonstrating the positive impact of a dietary phenolic-rich food that can be utilized to improve bone health in postmenopausal females.”

Do Prunes Offer a Double Benefit?

Q. I’ve read that a recent study shows eating prunes can build bones. One hypothesis is that the vitamin K plus potassium and magnesium may help with bone remineralization. The suggested “dose” is 4-6 prunes/day (ideally 6) spread out over the day.

What can you tell us about this approach, other than likely cautions about easing into this consumption? (Given Americans’ issues with constipation and common reliance on laxatives, prunes would seem to offer a double benefit.)

A. You have apparently read about the Prune Study. In this randomized trial, 235 postmenopausal women were randomly assigned to eat no prunes, 50 g or prunes or 100 g daily. Over a year, bone mineral density of the hip decreased in the women on their regular no-prune diet, but those consuming prunes maintained their bone mineral density (BMD).

The drop-out rate was 40 percent among women who were supposed to be eating 100 g of prunes daily. We suspect the intestinal effect of so many prunes could be overwhelming. A previous study suggested that 50 g of prunes a day was as helpful for bone density as 100 g (Osteoporosis International, July 2016).  Other dried fruits such as black currants may also help preserve bones (Nutrients, Nov. 23, 2022).

Is There a Problem with Too Many Prunes?

Q. I have read that prunes have health benefits. For one thing, they keep you regular. They are also supposed to strengthen bones.

I am confused about the “dose.” How many prunes do you need to eat to get health benefits? Too many give me diarrhea.

A. The Prune Study (American Journal of Clinical Nutrition, Oct. 6, 2022) reported that people who ate four to six prunes daily improved bone density over six months.

Investigators asked the “high-dose” experimental group to eat twice as many prunes. The researchers acknowledged that the drop-out rate among these women was 41 percent, due in part to “poor tolerance consuming the prunes.” We suspect that eight to twelve prunes would cause many people diarrhea.

Some readers have pointed out that prunes are sweet. They worry that consuming half a dozen prunes a day might raise blood sugar, especially for people with diabetes. With their high fiber content, however, prunes have a low glycemic index. As a result, a serving of four to six unsweetened prunes should not raise blood sugar too much.

Previous Research on Prunes and Bone Health:

The best-recognized health benefit of eating prunes is regularity. However, a previous study suggested that people who eat dried plums may have less bone loss (Journal of Medicinal Food, Oct. 2019). An earlier study found that women eating prunes every day for a year had better bone mineral density five years later (Nutrients, May 14, 2017). A review suggested that prunes might alter the balance of bone remodeling cells (Nutrients, April 19, 2017).

There is evidence that prunes have both anti-inflammatory and antioxidant activity (Advances in Nutrition, Jan. 3, 2022). There is also some suggestion that prunes may help lower blood pressure and cholesterol (Pharmaceutical Biology, Dec. 2017; JAMC, Jan-March, 2010).

None of these studies reported adverse effects. Given the known impact of eating prunes on bowel habits, though, people might want to start at a low dose and increase gradually. Perhaps it’s time to stop calling prunes the “funny fruit” and start calling them “Power Prunes.”

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