Old Teeth Tell New Stories About People Who Didn’t Get Enough Sun

http://www.nytimes.com/2016/07/20/science/teeth-vitamin-d-deficiency-archaeology.html

Version 0 of 1.

You don’t just have teeth in your mouth: You have around 32 fossils that tell a microscopic history of your health. And scientists have found that even the old, discarded, not-so-pearly whites of people that lived hundreds of years ago tell a story about them, too.

According to a paper published Monday in The Journal of Archaeological Science, the researchers discovered a permanent record of vitamin D deficiency in the microscopic structure of old teeth and shed new light on the daily challenges faced by people of the past.

When the body doesn’t get enough vitamin D from the sun or food, they found, teeth develop gaps or bubbles in dentin, the layer under enamel that makes up about 85 percent of a tooth’s structure. These abnormalities reveal stories not just about past environmental conditions or food availability, but about culture and society as well.

Throughout history and across the world, there have been epidemics of children with rickets, a disease characterized by bowed legs and deformed hips, caused in part by a lack of sunlight. Anthropologists have identified rickets outbreaks by examining skeletal remains in places at high latitudes with limited access to sunlight, like some in England, Canada or France. But the vast majority of children who had rickets will outgrow it. That makes the dental record of the condition important because abnormalities within teeth don’t disappear with age, as evidence of bowed legs, for example, can, in adult bones. Understanding rickets outbreaks in the past can help in the study of children’s health today.

The researchers, led by Megan Brickley, an anthropologist at McMaster University in Hamilton, Ontario, examined the skeletal remains of six individuals who had been buried in the 18th and 19th centuries in cemeteries known to contain cases of rickets and individuals who had survived childhood vitamin D deficiencies. The team determined who likely had rickets from their bones and then analyzed their teeth, cutting each tooth into several transparent slices, thinner than a sheet of tissue paper, and examining them under microscopes.

They found that a 24-year-old man who had been buried in Quebec between 1771 and 1860 had suffered four bouts of rickets in his short life: twice before the age of 2, once again around the age of 6, and again, in a somewhat severe episode, around the age of 12. Evidence of this final episode in his third molar correlated with an abnormal curvature in his tailbone that only could have developed around the same time.

“We were able to see inside that tooth, what was housed in there, years ago,” said Dr. Brickley.

They reached this precision because teeth develop at different rates and leave behind concentric circles like tree rings over time. The researchers could look at the abnormalities within those layers to estimate occurrence and severity.

“You can’t get that info from a skeleton,” said Lori D’Ortenzio, a paleopathologist who worked on the study.

Lynne Schepartz, an anthropologist at the University of the Witwatersrand in South Africa who specializes in prehistoric health and was not involved in the study found the results exciting. Studying vitamin D deficiencies in teeth, she said, could reveal information about limited access to sunlight among certain populations as a result of labor roles, culture or social status.

But the insights aren’t limited to the past. It’s estimated that more than a billion people worldwide don’t get enough vitamin D, and around the world rickets still can affect up to 9 percent of the childhood population in some places. Knowing about the past and lifestyle factors that led to rickets in particular communities worldwide may help put what’s happening today into historical context.

In Britain, for example, rickets is on the rise. The fact that vitamin D deficiency could be recorded in teeth, “was certainly news to me,” John Middleton, president of Britain’s Faculty of Public Health, wrote in an email.

“We are concerned about dietary deficiency, lack of dairy, fish and meat, and particularly lack of sunlight for children who spend all their time indoors watching TV or playing video games,” he said.

This may not be so abnormal — in the past, Victorian smog, poor nutrition, working indoors, and clothing that covered most of the body contributed to rickets. Now with records from teeth, it’s possible to find even more cases in adults that were previously missed.

The opportunity to access never-before-told stories trapped within molars that started growing when a fetus was still inside the womb also may contribute to conversations around an idea called the Barker Hypothesis, which says that conditions in the womb contribute to development of diseases later in life.

The World Health Organization currently warns mothers about vitamin D deficiency, which is common during pregnancy and linked to poor health outcomes for both mother and child. Dr. Brickley said archaeological evidence from the molars of those no longer living could provide new links between prenatal vitamin D deficiency and early death or chronic disease.