Researchers from McMaster University in Hamilton have come up with a new method of peering into the lives of people who lived hundreds of years ago -by analyzing their teeth.
A team led by Lori D’Ortenzio of McMaster’s Department of Anthropology compared the teeth of contemporary control subjects to teeth from skeletal remains of people buried in rural Quebec and France in the 1700s and 1800s and were able to determine clear evidence of vitamin D deficiency.
Obtained through exposure to sunlight and via foods such as fatty fish, egg yolks and products like fortified milk and orange juice, vitamin D is essential for the absorption of calcium and thus is crucial to the development of healthy bones and teeth. Vitamin D deficiency has been associated with mood disorders (depression) and cognitive impairment, cancer, cardiovascular disease, aches and pain and tiredness, while severe vitamin D deficiency leads to rickets, a condition that produces softening and deformation of the bones.
The common approach to detecting vitamin D deficiency in ancient skeletal remains has been to examine the bones themselves, looking for typical bowing or deformation, but the method has proved unreliable, as bones are remodeled over the course of a person’s life and thus sometimes hide details connected to prior injury or illness. Plus, bones break down in soil.
But teeth contain dentin, which does preserve a record of health and illness over the course of a person’s life and, luckily, dentin is protected by a tooth’s dental enamel. Much harder than bone, enamel keeps the interior dentin intact well after death, making teeth the perfect source for a person’s medical history long after they have passed away.
“They’re essentially fossils in your mouth,” says author Bonnie Kahlon, a Lab Co-Ordinator in McMaster’s Department of Anthropology. Using scanning electron microscopy, researchers were able to examine thin sections of teeth to show anomalies in the dentin layers which tell the tale of vitamin D deficiency -in one Quebec man who died at age 24, the team was able to pinpoint that he had suffered four separate bouts of rickets before he had turned 13. And, importantly, the team’s method was confirmed by experts analyzing the actual bones of the deceased who concluded that the subjects did, in fact, suffer from rickets.
“The layers store what happens as teeth grow,” says D’Ortenzio. “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.”
Canada’s northerly climate makes it difficult for most people to get enough vitamin D from exposure to sunlight alone (and the small amounts in foods are not enough to suffice). Osteoporosis Canada recommends routine vitamin D supplementation for everybody from breastfeeding infants to children and adults. A recent study found that one-third of Canadians had vitamin D levels in their blood lower than the minimum level sufficient to maintain healthy bones, with 40 per cent found to be below the cut-off level in winter and 25 per cent in summer.