Vitamin D deficiency: cause of autoimmune diseases, such as diabetes? 🌞

As countries in the northern hemisphere prepare for the low vitamin D season, those months during which sunlight is too weak to stimulate the production of this vitamin in the skin, a study explains why a vitamin D deficiency early in life is associated with greater vulnerability to autoimmune diseases.


During childhood, the thymus helps immune cells differentiate between body tissues and dangerous intruders. A research team has discovered that at this stage of life, a deficiency in vitamin D leads to the premature aging of the thymus.

"An aging thymus causes 'leaks' in the immune system," explains John White, principal author of the study and chair of the Department of Physiology at McGill University, where he teaches. "The thymus then loses its effectiveness in filtering out immune cells that might mistakenly attack healthy tissues, increasing the vulnerability to autoimmune diseases, such as type 1 diabetes."

Scientists have known for years that vitamin D aids calcium absorption, which strengthens bones, and recent research has revealed this vitamin's critical role in regulating the immune system, says Dr. White.

"Our study clarifies this role and may lead to new strategies for preventing autoimmune diseases."

Although the research was conducted on mice, the findings are still relevant for humans, as the thymus functions similarly in both species, he adds.

The importance of supplementation

Published in Science Advances, the study highlights the importance of adequate vitamin D intake, particularly in children.

"In cities like Montreal, where sunlight-driven vitamin D production stops from late fall to early spring, supplementation is crucial," stresses Dr. White. "If you have a young child, it is important to consult a healthcare professional to ensure they are getting enough."

This breakthrough builds on a 2001 Finnish study, which followed over 10,000 children and found that those who received vitamin D supplements early in life were up to five times less likely to develop type 1 diabetes later in life.

Finland, where natural vitamin D production is halted for long periods, was an ideal location to study the multiple roles of this nutrient, notes John White.

In the McGill study, scientists tested mice incapable of producing vitamin D to examine the effects of this deficiency on the thymus: using cellular analyses and gene sequencing, they observed the repercussions on the immune system.

In future studies, Dr. White plans to investigate the effects of vitamin D on the human thymus—an area that has yet to be explored, he points out.

The study was funded by the Canadian Institutes of Health Research and Genome Canada.