As few as four prunes a day can protect you against age-related bone loss, and reduce the risk of fractures, new research has found.

Further, those weird and sticky treats – a popular go-to for stool softening – may also protect bone structure and strength.

This will be a surprise for people who think calcium, especially from dairy foods, is the key to preserving bone health.

But calcium deficiency is just one part of the story about how bones become weaker and more prone to fracture.

The curse of inflammation

Oxidative stress and inflammation – which tend to increase with age – also contribute to bone loss. This is especially the case in post-menopausal women.

This is because estrogen, critical for bone health, declines during menopause. The loss of the hormone hastens bone density. And as bone strength or density decreases, people are much more likely to develop osteoporosis or have fractures.

Mary Jane De Souza is distinguished professor of kinesiology and physiology at Penn State. She’s also the corresponding author of the new paper.

In a statement, she said there is medication available to treat osteoporosis. But many women don’t take it.

“Prunes offer a promising alternative,” De Souza said.

It’s thought that plums blunt the inflammatory pathways that lead to bone loss. Because they contain bioactive compounds such as polyphenols – which have anti-inflammatory properties.

It’s also thought that prunes might work against bone loss because they contain high levels of vitamin K, which supports bone health.

Low intake of vitamin K can increase the risk of lower bone density and fracture.

“In our study we saw that daily prune consumption impacted factors related to fracture risk. That’s clinically invaluable,” she said.

The new study

According to a statement from Penn State: The research team conducted a 12-month randomised controlled trial with 235 post-menopausal women. Participants were assigned to one of three groups:

• Those who ate no prunes
• Those who ate 50 grams, or four to six, prunes daily
• Or 100 grams, or 10 to 12, prunes daily.

Every six months, the women were assessed using a peripheral quantitative computed tomography. This is a scan that allows for cross-sectional imaging.

The researchers were able to measure 3D bone mass density, bone geometry and bone strength.

The results

Over the course of one year, the researchers found:

• Measures of bone mass density and bone strength at the tibia, or shin bone, all decreased in women in the control group. (Those who ate no prunes)
• In contrast, those who ate at least four to six prunes every day maintained bone density and bone strength and preserved bone structure, particularly in cortical bone.

Although women in both prune groups saw benefit, four to six prunes a day “may be the more feasible dose”.

Women in the 100-gram group dropped out of the study at a higher rate. This was because they got bored from having so many prunes in their daily diet.

“It’s pretty exciting data for a 12-month study,” De Souza said.

“We were able to maintain and preserve bone at the weight-bearing, cortical bone of the tibia and the maintenance of cortical bone and bone strength is key to avoiding fracture.”

Other benefits

Prunes can help control appetite and reduce overall caloric consumption.

Being rich in Vitamin A, they also protect your eyes against macular degeneration.

They may help lower your blood sugar. Because they don’t have the candied quality of other dried fruit.

They are a good source of iron, which helps stop your hair falling out.

And they’re packed with more antioxidants than blueberries.

Oh, and like bananas they’re a great source of potassium, which helps maintain a steady heartbeat and lowers blood pressure.