Little Ice Age cooling in Europe may have raised the risk of rickets

Previous skeletal studies suggest that rickets became more common among Europeans during the 18th and 19th centuries. One culprit may have been the Industrial Revolution, when many Europeans lived in UV-poor polluted cities and often worked indoors. The unusually cold climate may have added “an extra layer of difficulty” to getting enough sunlight, says Ellen Kendall, a bioarcheologist at Durham University in England

The Little Ice Age was a period of global cooling from the 13th to 19th centuries caused by extreme solar cycles and a series of volcanic eruptions, which can cool the planet by ejecting aerosols into the atmosphere that block sunlight. In the last 200 years of the era, 18 major eruptions helped spur a temperature drop of 2 to 3 degrees Celsius over northern Europe.

Kendall and colleagues wondered how this cold climate affected health. They examined calcium deposition — how the essential mineral is incorporated into bones — in the remains of 21 people buried from 1711 to 1829 in the town of North Shields. Calcium often doesn’t fully mineralize in people with vitamin D delicacies, leaving voids in teeth as they grow.

The team found bands of failed calcium mineralization in the teeth, suggesting seasonal spates of vitamin D deficiencies. Some skeletons also showed signs of rickets. North Shields was a small rural town that hadn’t yet undergone industrialization, so these deficiencies probably weren’t due to bad air conditions.

The unusually cold weather may have changed people’s behavior during the winter, Kendall says. Residents may have kept their kids indoors or bundled them up so that little skin was exposed when they did go outside, preventing them from getting enough UV light, she says.

However, climate was still just one factor among many — including gender roles, diet and pollution — that shaped vitamin D deficiencies at the time, says Kendall. “Humans are very messy to study,” she says. “That’s one of the things that makes them so very fascinating.”

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