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Vitamin D’s Role In The Immune System

November 19, 2020

We’ve always been told that we get vitamin D from sun exposure. Perhaps you’ve heard the common rule that everyone needs 15 minutes of sunlight per day in order to maintain healthy levels of vitamin D. But have you ever wondered why it’s such an important nutrient?

Our bodies make vitamin D in the skin through a sunlight-activated biological pathway. UVB rays penetrate the outer layers of skin and help produce vitamin D3, which is then converted to its active form, 25-hydroxyvitamin D, in the liver. Overall vitamin D levels are usually measured by the amount of 25-hydroxyvitamin D in the blood. [Chambers]

Vitamin D has a well established role in bone health as a vital part of the calcium-absorption process. When there are low amounts of calcium in the bloodstream due to a lack of absorption capacity, the body sources calcium from the skeleton, causing weak bones and joints. Vitamin D deficiency is therefore a very common cause of musculoskeletal pain and is associated with arthritis and frequent fractures. [Vasquez]

Vitamin D’s importance for bone health may be close to common knowledge, but it’s similarly vital role in regulating the immune system is less known. Vitamin D is essential for immunomodulation, which is the process of adjusting the immune response to the desired level.

Immunomodulation is especially important for patients suffering from autoimmune diseases, where one’s immune system attacks their own body and causes a myriad of health issues. Some common autoimmune diseases include type 1 diabetes, lupus, Crohn’s, multiple sclerosis, and Hashimoto’s. Autoimmune diseases are the third leading cause of death in the United States, only surpassed by cancer and heart disease. [Vasquez]

Our immune systems are run by T cells, which you can read more about in this blog post. The thymus (T) produces T cells, which can then be converted into one of 3 different specific types. Effector T cells help to expel pathogens, but they can also be responsible for overactive immune responses by attacking self-antigens. Antigens are usually foreign substances that dendritic cells process and present to T cells and initiate the immune response. When a normal body cell is interpreted as an antigen (self-antigen), effector T cells attack. This is considered an autoimmune reaction.

T-regulatory cells (T-regs), a second type of T cell, are responsible for policing effector T cells and halting an autoimmune attack. Therefore, promoting T-reg synthesis is of utmost importance for those with autoimmune diseases. For example, Immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX syndrome) is a fatal autoimmune disease characterized by a mutation in the gene FoxP3 that promotes T-reg synthesis. In other words, the inability to create a sufficient amount of T-reg cells can be deadly. [Chambers]

So we’ve established that T-regulatory cells are vitally important for modulating (regulating) the immune system. The amount of basic T cells that are converted to T-reg cells is determined by gene expression. Our genes are encoded in our DNA and are the blueprints for all bodily cells, functions, and responses. Though it is a common understanding that our DNA is unchangeable, the emerging field of epigenetics tells us otherwise.

Epigenetics is the study of how environmental factors inside and outside of the body can affect gene expression. Simply put, even though the FoxP3 gene may be present, the extent to which it is employed for the production of T-reg cells is very dependent upon environmental factors. Stress and toxins, for example, inhibit the production of T-regs (Cortisol). Vitamin D, however, does the opposite. Vitamin D supplementation has been shown to significantly increase the percentage of T-reg cells, even in healthy individuals [Prietl et. al.]. It is an important nutrient for promoting T cells’ conversion to T-regs as opposed to the other possible T cell types, such as effector.

Vitamin D is also vital for the process of wound healing and is especially important for maintaining the integrity of mucosal barriers in the intestinal tract [Kong]. Vitamin D deficiency can lead to something called “leaky gut” which also can cause inflammation in the body. Inflammation is one of the most common root causes of disease.

When the intracellular junctions in the intestinal lining are compromised from vitamin D insufficiency, microbes and food antigens leak into the bloodstream and can cause an immune response in the form of inflammation, allergy, or autoimmunity [Vasquez]. With one third of all US adults having insufficient vitamin D levels [CDC], it’s not surprising how prominent leaky gut syndrome is. It’s been linked to a wide range of conditions that may outwardly seem unrelated, but upon further investigation can be traced to leaky gut. These conditions can include bloating, abdominal pain, food sensitivities, ADD, brain fog, memory loss, joint pain, psoriasis, eczema, and autoimmune disease, just to name a few.

Vitamin D is an anti-inflammatory phytonutrient; it inhibits proinflammatory processes by suppressing the overactivity of immune cells through promotion of T-regs [Vasquez]. Along with vitamin D, diet is one of the most important factors in preventing inflammation. The average American diet is full of inflammatory foods. Since chronic inflammation is a disease-causing agent, physicians recommend an anti-inflammatory diet called the Five-Part Supplemented Paleo-Meditteranean Diet. One of the core principles of this diet is supplementation with vitamin D3 at 2,000- 4,000 IU/day [Vasquez]. However, vitamin D should be dosed depending on the patient’s needs and may require higher levels than 4,000IU/d. Vitamin D is critical and is so termed a “goldilocks nutrient”, which means if it is too high or low, it will promote problems for the immune system.

Its role in bone health, immunomodulation, and preventing leaky gut syndrome make vitamin D an absolutely essential nutrient, especially in autoimmune cases. However, even generally healthy individuals can benefit from supplementation. It’s no wonder, then, that Dr. Alex Vasquez states in his book Functional Immunology and Nutritional Immunomodulation, “Routine measurement and/or empiric treatment with vitamin D3 needs to become a routine component of patient care.” The benefits of vitamin D supplementation are very well established and critical to anyone with an autoimmune condition.

Ian Hollaman, DC, MSc, IFMCP

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