How Vitamin D Deficiency Can Lead to Autoimmune Diseases

As Canadians prepare 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 in early life is associated with a higher risk of autoimmune diseases.

During childhood, the thymus helps immune cells distinguish between the body’s own tissues and harmful invaders. Vitamin D deficiency at this stage of life causes the thymus to age more quickly, researchers found.

The study is published in the journal Scientific advances.

“An aging thymus causes the immune system to ‘leak,'” said lead author John White, professor and chair of the Department of Physiology at McGill. “This means the thymus becomes less effective at filtering immune cells that might mistakenly attack healthy tissue, increasing the risk of autoimmune diseases like type 1 diabetes.”

He noted that researchers have known for years that vitamin D helps the body absorb calcium for strong bones, and more recent research has discovered its crucial role in regulating the immune system.

“Our findings provide new clarity to this link and could lead to new strategies for preventing autoimmune diseases,” he said.

Although the research was conducted on mice, the findings are relevant to human health because the thymus functions similarly in both species, White added.

The importance of a substitute for sunlight

The findings highlight the importance of adequate vitamin D intake, particularly for children.

“In places like Montreal, where we stop producing the sun’s vitamins between late fall and early spring, supplementation is essential,” White said. “If you have a young child, it’s important to check with your health care provider to make sure they’re getting enough.”

This advance is based on a Finnish study from 2001, which followed more than 10,000 children. It found that children who received a vitamin D supplement from a young age had up to a five-fold lower risk of developing type 1 diabetes later in life.

Finland, with its long winter periods of vitamin D, makes an ideal case study for learning more about the many roles of this nutrient, White said.

In the McGill study, researchers used mice unable to produce vitamin D to examine how the deficiency affected the thymus, using cellular analysis and gene sequencing to see how this affects the immune system.

In future studies, White hopes to explore how vitamin D affects the human thymus, which he says has never been done before.