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Discover more about autoimmune diseases and why your vitamin D levels are an important link to these conditions.

Protection and our immune system go hand in hand. With three lines of defence, the immune system has various mechanisms that help guard against infection and disease. But what happens when the immune system malfunctions and can no longer distinguish between what is harmful and what is not? Read on to discover more about autoimmune diseases and why your vitamin D levels
are an important link to these conditions.


The immune system is a complex set of organs, cells, and protective proteins (antibodies) that safeguard the body from damaging pathogens and substances such as viruses, bacteria, and toxins. Imagine your immune system as a fortress, always trying to defend against attacks from foreign intruders that are not welcome. However, when the fortress crumbles, its securities deteriorate, and trespassers can invade. The same holds for the immune system. Abnormalities in the immune system can negatively impact its protective measures, leading to autoimmunity. In autoimmunity, the immune system produces “autoantibodies” that mistakenly attack the body’s healthy organs, tissues, and cells.

Autoimmunity can lead to autoimmune diseases, but this is not always true. Research has identified specific triggers that can cause some individuals with harmless autoimmunity to develop harmful autoimmune diseases, including, but not limited to: 

  • Genetics 
  • Poor diet and lifestyle choices
  • Hormonal changes
  • Smoking
  • Exposure to pollutants
  • Infections
  • Increased stress levels
  • Shift work
  • Dysbiosis (gut microbiota imbalance)

Approximately 100 auto-immune diseases have been identified, impacting one or more body parts and triggering symptoms such as fatigue, hair loss, skin rashes, joint pain, and digestive issues. The suffering faced by individuals with autoimmune diseases is undeniable as they continuously deal with challenges to their quality of life, along with potential financial burdens.


As a nutrient and hormone, vitamin Dis widely known to influence bone and overall health. Research has shown that vitamin D status is also linked to cardiovascular disease, type 2 diabetes, and infections. Among the different triggers of autoimmune diseases, vitamin D deficiency has also been highlighted as a cause. 

With its ability to regulate immune function and inhibit inflammation, it’s unsurprising that vitamin D resistance and low vitamin D levels are associated with autoimmunity and increased autoimmune disease risk and severity. Specifically, vitamin D, along with the vitamin D receptor, can influence innate and adaptive immunity by regulating different immune cells, such as T cells, B cells, monocytes, and macrophages. Interestingly, autoimmune diseases such as type 1 diabetes, inflammatory bowel disease (IBD), and celiac disease are more prevalent in northern latitudes with limited sun exposure and vitamin D deficiency.


Mounting evidence suggests that vitamin D supplementation can reduce the incidence of autoimmune diseases and improve treatment. In a nationwide, randomized, double-blind, placebo-controlled trial (the VITAL study) that included 25,871 participants, researchers discovered that vitamin D3 supplementation (50 mcg [2000 IU] daily for five years) with or without omega-3 fatty acids significantly reduced confirmed autoimmune diseases by 22%. In addition, omega-3 fatty acid supplementation with or without vitamin D reduced autoimmune diseases by 15% (not statistically significant). Interestingly, both vitamin D and omega-3 fatty acid supplementation decreased autoimmune diseases by about 30% compared to the placebo. Although we can get vitamin D through sun exposure and dietary sources such as oily fish, eggs, and mushrooms, vitamin D3 supplements provide a reliable approach to preventing and treating deficiency. 


Maintaining vitamin D levels throughout life is vital, yet research shows that 37% of the Canadian and 24% of the U.S. populations have insufficient levels of vitamin D. Despite the numerous causes of low vitamin D, it is well-known that supplemental vitamin D is connected with higher vitamin D status. But how much do you need daily? Vitamin D recommendations vary across different countries, with dosages ranging from 10 mcg to 62.5 mcg (400–2500 IU) daily. An important indicator of vitamin D levels in the body is 25-hydroxyvitamin D (25(OH)D), which can be easily tested to determine vitamin D status and daily requirements. Check out the following chart to learn the meaning of 25-(OH)D measures.

Vitamin D (25-(OH)D) Vitamin D Status
Less than 30 nmol/L (12 ng/mL) Vitamin D deficiency (severe)
30–50 nmol/L (12–20 ng/mL) Insufficient vitamin D levels for bone and overall health
Greater than 50 nmol/L (greater than 20 ng/mL) Sufficient vitamin D levels for bone and overall health
Greater than 125 nmol/L (greater than 50 ng/mL) High vitamin D levels linked to possible adverse effects

At present, the optimal vitamin D status for immune function is not clear; however, research points to the value of high dosages of vitamin D for autoimmune disease and other benefits beyond those for bone health. If you are concerned about autoimmunity and autoimmune diseases, discuss the importance of knowing your 25(OH)D status with your health care practitioner. With this information, you can develop a personalized vitamin D supplementation plan to support your immune system and quality of life.