As Canadians brace for "vitamin D winter" - months when the sun's angle is too low to produce the vitamin in the skin - a McGill University study explains why vitamin D deficiency early in life is associated with a higher risk of autoimmune diseases.
During childhood, the thymus helps train immune cells to distinguish between the body's own tissues and harmful invaders. A vitamin D deficiency at that stage of life causes the thymus to age more quickly, the researchers discovered.
"An aging thymus leads to a leaky' immune system," said lead author John White, a Professor in and Chair of McGill's Department of Physiology. "This means the thymus becomes less effective at filtering out immune cells that could mistakenly attack healthy tissues, increasing the risk of autoimmune diseases like Type 1 diabetes."
He noted that researchers have known for years vitamin D helps the body absorb calcium for strong bones and that more recent research has discovered its crucial role in regulating the immune system.
"Our findings bring new clarity to this connection and could lead to new strategies for preventing autoimmune diseases," he said.
Although the research was conducted with mice, the findings are relevant to human health because the thymus functions similarly in both species, White added.
The importance of a sunlight substitute
The findings, published in Science Advances, highlight the importance of adequate Vitamin D intake, especially for children.
"In places like Montreal, where we stop making the vitamin from sunlight between late fall and early spring, supplementation is key," said White. "If you have a young child, it's important to consult with your health-care provider to ensure they're getting enough."
The breakthrough builds on a 2001 Finnish study, which followed more than 10,000 children. It found that children who were supplemented early in life with vitamin D had up to a five-fold-lower risk of developing Type 1 diabetes later in life.
Finland, with its long periods of vitamin D winter, served as an ideal case study to learn more about the nutrient's many roles, said White.
In the McGill study, researchers used mice that couldn't produce Vitamin D to examine how the deficiency affected the thymus, employing cell analysis and gene sequencing to see how it impacts the immune system.
In future studies, White hopes to explore how vitamin D affects the human thymus, something he notes has not been done before.
The study was funded by The Canadian Institutes of Health Research and Canada's Genome Enterprise.
