Treatment with friendly bacteria widely used in probiotic supplements can strengthen bones, as research has shown.
Healthy mice fed with Lactobacillyus rhamnosus GG (LGG) shoots experienced an immune response that stimulated bone density growth.
The effect was related to the production of butyrate or butyric acid – a type of fatty acid produced by intestinal bacteria.
This, in turn, activated regulatory T cells, part of the immune system.
Researchers hope that the discovery will lead to new treatments for bone osteoporosis.
A condition, a serious threat to postmenopausal women, can lead to exclusion of bone fractures and an increased risk of death.
Earlier animal studies have suggested that probiotics may help prevent bone loss associated with the disease, but the researchers were not sure exactly why.
Professor Roberto Pacifici, from Emory University in the USA, who conducted new research, said: "Because their mechanism of action in the bone is unknown, they are treated as a kind of alternative, esoteric, untested treatment.
"Our goal was to identify the biological mechanism of action of probiotics, a mechanism that makes sense for traditional scientists, hoping that thanks to this probiotics will become the main treatment".
The team found that four weeks of LGG supplementation accelerate bone formation in female mice by stimulating the growth of buttermilk-producing intestinal bacteria.
LGG had no effect on bone mass when the mice were cultured in a germ-free environment, indicating that this was effective in combination with other intestinal insects.
Both LGG and butyrate induced the expansion of regulatory T cells in the bone marrow.
The T cells, in turn, secrete a protein called Wnt10b, which is known to be critical to bone development, the researchers described in the journal Immunity.
Professor Pacifici said: "We were surprised by the potential of the intestinal microbiome (bacterial population) in regulating bone and the complexity of the mechanism of action of probiotics.
"In general, there is a strong interest in the concept that intestinal bacteria regulate the function of distant organs." As it happens, it is largely unknown.
'We described a detailed mechanism by which changes in the composition of the intestinal microbiome induced by probiotics affect a distant system such as the skeleton.'
Lactobacillus rhamnosus GG is widely marketed as a non-prescription probiotic. It is said that it balances the immune system, protects against allergies and IBS and helps prevent infection. There are also claims that it has anticancer properties.
The team is now planning to expand the study and investigate whether butyrate supplementation can overcome osteoporosis.
Professor Pacifici added: "Our findings will have to be validated in human studies.
"If successful, this research can justify the use of butyrate or probiotics as a novel, safe and inexpensive treatment to optimize skeletal development in young people and prevent osteoporosis in the elderly."
– Press Association