Toronto: Researchers have found that vitamin D deficiency caused majorly by lack of exposure to sun may reside in the teeth of every human being and remain viable for hundreds of years or more. The findings showed that the teeth can act as an essential fossil and help anthropologists to sneak into the lives and challenges of people who lived hundreds of years ago and whose only record is their skeletal remains. When the body is deprived of vitamin D, permanent microscopic abnormalities form in the layers of dentin -- the tooth structure under the enamel can create an ongoing record that can later be read like the rings of a tree. "The layers store what happens as teeth grow. We all know the importance of vitamin D, but until now we did not have such a clear way of measuring exactly what happened to people, and when," said Lori D'Ortenzio, doctoral candidate at McMaster University in Ontario, Canada. "They're essentially fossils in your mouth," added Bonnie Kahlon, Lab Technician. Until now, scientists trying to understand historical patterns in vitamin D deficiency have had to use bones, which are problematic sources of such information. However, dentin is not remodelled, and dental enamel -- much harder than bone -- protects the dentin long after death, making teeth a rich and accurate source of archaeological information. "If we can properly understand past changes in deficiency levels, we can evaluate where we currently are and move forward," added Megan Brickley, Professor at McMaster University. Vitamin D deficiency can also cause rickets -- a softening and weakening of bones in children, usually due to inadequate vitamin D. It is a serious public health issue affecting some one billion people worldwide, the researchers said. Most cases of rickets are caused by a lack of sun exposure, with effects that can include pain, bone deformities and failure to achieve or maintain adequate bone levels. For the study, published online in the Journal of Archaeological Science, the team compared the teeth of modern-day control subjects to teeth extracted from bodies buried in rural Quebec, Canada and France in the 1700s and 1800s. Their analysis showed that one Quebec man had suffered four bouts of rickets in his 24 years of life -- all before he turned 13. Examining thin sections of the teeth under a microscope and using technology at the McMaster-based Canadian Centre for Electron Microscopy, the researchers were able to show that anomalies formed in the dentin layers during years when victims failed to get enough Vitamin D to fully mineralize the structures that form dentin and bone.