July 11, 2013
Lack Of Vitamin D Causes Bone Aging
Brett Smith for redOrbit.com - Your Universe Online
Parents who yell at their kids to "go out and play" this summer may want to follow their own advice. A new study from US Department of Energy's Lawrence Berkeley National Laboratory has found bone aging can be accelerated from a lack of vitamin D.
Synthesized when the skin is exposed to the sun's rays, vitamin D conveys numerous other health benefits including lowering the risks of multiple sclerosis and rheumatoid arthritis in women. Conversely, vitamin D deficiency has been linked to a higher risk of bone fracture and lower bone quality.
"The assumption has been that the main problem with vitamin D deficiency is reduced mineralization for the creation of new bone mass, but we've shown that low levels of vitamin D also induces premature aging of existing bone," said Robert Ritchie, a material scientist at the Berkeley Lab.
When the body's vitamin D levels become deficient, it reacts by removing calcium from bones to maintain necessary calcium blood levels. This robbing of bone calcium disrupts the mineralization process needed to create new bone mass.
In adults, prolonged vitamin D deficiency can cause painful osteomalacia (rickets), a condition marked by a softening of the bones, muscle weakness, and a greater risk of bone deformation and fracture. Vitamin D treatments and calcium supplements have only been shown to be partially effective in treating the condition, indicating other factors also play a role.
According to the Berkeley team and their international collaborators' report in the journal Science Translational Medicine, the scientists began their study by gathering samples of pelvic bone cores from 30 participants. Half of the volunteers were diagnosed as vitamin D deficient and showed early signs of osteomalacia.
The bone samples were sent from Germany where they were collected to the Berkeley Lab for analysis using Fourier Transform Infrared (FTIR) spectroscopy and X-ray computed micro-tomography.
After performing a chemical and structural analysis, the team "measured the resistance to crack growth and by following crack growth in real-time were able to observe how cracks and structure interact," Ritchie said.
"This enabled us to relate mechanical properties to specific structural changes," he added.
The team found their vitamin D-deficient subjects had less overall mineralization on the bone surface, yet more heavily mineralized and older looking bone below the surface.
"These islands of mineralized bone were surrounded by a collagenous boundary that prevented them from being properly remodeled," said co-author Bjorn Busse, of the Department of Osteology and Biomechanics at the University Medical Center in Hamburg, Germany. "Cut off from a supply of osteoclasts, the cells that normally remodel the bone, these isolated sections of mineralized bone begin to age, even as overall bone mineralization decreases from a lack of calcium."
"Fracture mechanics measurements and CT-scanning of the crack path indicated that vitamin D deficiency increases both the initiation and propagation of cracks by 22- to 31-percent," Ritchie said.
The study authors recommended that vitamin D levels be regularly monitored and maintained at healthy levels to prevent defective mineralization that can lead to premature aging and a higher risk of fractures.