Can Prunes Reverse Bone Loss?

Eleanor writes:

“Can you comment on the benefits of prunes to stimulate bone growth? There are a lot of sites promoting prunes as a scientifically proven way to ward off osteoporosis. I’d love it if you would give these claims a critical look.”

There has been quite a bit of research done on dried plums (aka prunes) and their effects on bone health. Some of the results have been quite impressive. One study, for example, found that subjects who had already experienced substantial bone loss were able to completely reverse these losses by eating prunes every day! Others show that eating prunes can help prevent the bone loss from occurring in the first place.

The only problem is that these studies were all done in mice and involved eating prunes as 25% of the entire diet.  I’ll just give you a moment to contemplate the potential impact of that.

Can Prunes Prevent Bone Loss in Humans?

There have also been a few trials involving actual humans. One compared the effects of eating 100 grams of prunes with 75 grams of dried apples on bone mass in women who were post menopausal. The study went on for one year, during which both groups also took calcium and vitamin D supplements. Both groups experienced similar increases in the bone density of their hips and thigh bones; the group eating the prunes had slightly better results in their spines and forearms. While the difference at those two sites was statistically significant, I’m not sure it was all that meaningful.  

Unfortunately, the study did not include a group that just took calcium and vitamin D without eating any dried fruit. That makes it hard to say whether either the prunes or the dried apples offered any substantial benefit above and beyond the supplements.

A hundred grams of prunes, by the way is about 12 prunes, which amounts to about 240 calories. The women in this study did not experience any significant weight gain over the course of the year.  Still, if that sounds like more prunes than you care to eat every day, a subsequent study found that eating half that many prunes each day works just about as well as eating a full 100 grams. Again, however, the positive effect—while statistically significant—was modest.

The most recent human study asked whether eating prunes would enhance the positive effect of resistance or weight training on bone mineral density. It didn’t.

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What’s in Prunes that Helps Bones?

Prunes contain several nutrients known to have a positive influence on bone health, including vitamin K, boron, potassium, and various antioxidants. You can get all of these nutrients from other sources, of course.  For example, 1/4 cup of broccoli gives you as much vitamin K as you’d get from the same amount of prunes.  A quarter of an avocado or six dried apricots has the same amount of boron as a 3-4 prunes. And an ounce of almonds or a half cup of kidney beans will give you at least as much potassium as a serving of prunes.

That said, prunes do have at least one unique benefit: they can be a very effective treatment for constipation.  If you appreciate that benefit—or you just enjoy prunes (I think they are delicious!), there’s no reason not to include them in your diet. But I think it's still too soon to conclude that prunes offer a unique and/or significant advantage in terms of preventing or reversing bone loss. At this point, the evidence remains limited and preliminary.

How to Maintain Healthy Bones

Whether or not you decide to make prunes a daily habit, here are my other best tips for maintaining strong bones:

• Be sure you are also eating a good variety or vegetables, nuts, and legumes, all of which provide the same sorts of bone-building nutrients as you get from prunes.
• Don’t skimp on protein. Your body needs protein in order to build and maintain strong, healthy bones.
• Consider taking a vitamin D supplement . Vitamin D is critical for both calcium absorption and bone formation and it is very difficult to get enough vitamin D from diet alone.
• Calcium supplements are needed only if you cannot get enough calcium from diet, and then I suggest taking only as much as you need to fill the gap between your diet and the recommendations. In most cases, this will be 250 to 500 mg per day.
• Exercise regularly and as vigorously as you safely can. Low-to-moderate impact, weight-bearing exercises such as walking, running, jumping rope, dancing, and tennis help build strong bones. Weight training or other resistance exercises such as elastic bands or tubes is also important. Finally, activities that increase balance and flexibility—such as yoga or pilates—are especially important as you get older.

Is there a study or trend that you’d like me to look into? Feel free to send me an email or post it on the Nutrition Diva Facebook page. You can also check the archives to see if I’ve already written about it. Just type your query into the box at the top of the page.