Unless you have been living under a rock, you have likely heard that the gut’s bacterial microbiome is now known to impact a myriad of crucial physiological processes in humans, including those occurring far from the intestines themselves. From proper serotonin signaling in the brain to staving off autoimmune diseases, the presence of certain strains of bacteria appears essential to maintaining a healthy body.  

Adding to that list, a new study published in the Journal of Internal Medicine suggests that the species Lactobacillus reuteri can help slow the progressive bone loss that occurs in older women with osteoporosis, thus reducing the risk of debilitating fractures.

The authors, a team of Swedish medical researchers, sought to evaluate a particular strain of Lactobacillus native to the human gastrointestinal tract – L. reuteri ATCCPTA 6475 – in the context of osteoporosis after past investigations in animals revealed the bacterium’s potent anti-inflammatory properties. Though the mechanism behind bone density loss in post-menopausal women remains unclear, it has been shown that inflammation stimulates the activity of a type of specialized cell, called an osteoclast, that breaks down the mineral lattice in bone.  

To test the microbe’s effects on a human skeleton, lead author Dr Anna Nilsson and her colleagues enrolled 70 women aged 75 to 80 years old with low bone mineral density (BMD) and randomly assigned each to take a daily oral dose of 10¹⁰ colony?forming units of L. reuteri 6475 (freeze-dried in a powder that can be mixed in a beverage) or placebo (maltodextrin powder) for one year.

At the end of the study, the women who took L. reuteri 6475 showed half as much bone mineral density loss as those on placebo, as measured by BMD of their shin bones. Moreover, the supplement was well-tolerated; women taking the placebo reported the same number of treatment reactions.

Proving or disproving the benefit of dietary supplements (or vitamins) is often difficult because many studies are retrospective; a design that can only identify correlation, not causation. The current study, on the other hand, may be small in sample size, but it is a randomized, placebo-controlled, double-blind (meaning no one, not even the authors, knew which intervention the subjects were receiving at the time) trial – the gold standard of scientific evidence.

Though preliminary, the results indicate that “[p]robiotic supplementation could be a new and promising concept for prevention of bone loss and osteoporosis,” the authors concluded.   

But of course, a lot more research awaits.

“This is the first study in humans,” Dr Nilsson told The New York Times. “We need confirmatory studies. And we’ve only studied one strain of L. reuteri, the type used in animal studies.”

Currently, a class of drugs called bisphosphonates is the primary treatment for osteoclast-driven bone loss. Though they get the job done, the side effects can be pretty terrifying.