Published June 2 2014
When most medical doctors test the vitamin D levels of their patients, their main concern is that a deficiency of this vitamin can affect bone health. This of course is true, as vitamin D is important for the absorption of calcium, which in turn is important for optimal health of the bones. However, vitamin D is also important for optimal immune system health, and there are plenty of research studies which confirm this. In addition, there is speculation that a vitamin D deficiency might actually be a trigger for developing an autoimmune condition, such as Graves’ Disease or Hashimoto’s Thyroiditis.
I just mentioned how most medical doctors who test the vitamin D levels of their patients do so out of concern that a deficiency will cause problems with bone health, and thus lead to a condition such as osteoporosis. And when you look at the lab reference ranges, the lower end of these ranges account for bone health. In most labs the reference range is somewhere between 30 and 100 ng/mL. Some labs will have the lower value as 25 ng/mL, while others will have the higher value at 80 ng/mL. But with regards to immune system health there is more and more evidence that the ideal range probably should be somewhere between 50 and 80 ng/mL.
Can Low Vitamin D Levels Cause Autoimmunity?
As for whether a vitamin D deficiency can cause autoimmunity, numerous studies show a correlation between low vitamin D levels and autoimmunity (1) (2). However, a lot of people who have low vitamin D levels don’t have an autoimmune condition. And I’m sure many of these people have a genetic predisposition for an autoimmune condition. Assuming this is true, then one can probably conclude that having a vitamin D deficiency alone won’t directly cause an autoimmune thyroid condition such as Graves’ Disease or Hashimoto’s Thyroiditis.
With that being said, if someone has a vitamin D deficiency, this will have a negative effect on their immune system health, and thus can make someone more susceptible to a trigger which in turn can cause an autoimmune response. So for example, one potential trigger of autoimmunity is exposure to a pathogen, such as H. Pylori. Many people with a genetic predisposition for an autoimmune condition are exposed to H. Pylori and other pathogens. But not everyone who becomes exposed to these pathogens develops an autoimmune condition. And a big factor behind this is the health of the person’s immune system. In fact, recent evidence shows that the vitamin D receptor plays an important role in gastric mucosa homeostasis and protection from an H. Pylori infection (3).
So when I work with someone who has deficient vitamin D levels, the vitamin D deficiency probably didn’t directly trigger an autoimmune response. But it very well could have been a big factor in making the person more susceptible to the trigger which did in fact cause their autoimmune condition. If this is true, then you can understand why it would be important to have EVERYONE routinely get their vitamin D levels tested. In my opinion this should be tested at least on an annual basis.
Of course there are other factors which are important for optimal immune system health. And so I’m not suggesting that if everyone maintained their vitamin D levels above 50 ng/mL that this would prevent all cases of autoimmunity. But when you consider the number of people who have autoimmune conditions, even if correcting vitamin D deficiencies led to a 5 to 10% decrease in autoimmune conditions it would be well worth looking into this. And so if you have children I would recommend getting their vitamin D levels tested. This is especially true in this day and age, as when I was a child I was playing outside frequently, and thus had a lot more sun exposure than most children of today. These days many children spend way too much time indoors watching television and playing video games, and therefore don’t get sufficient sun exposure.
How a Vitamin D Deficiency Affects The Immune-Gut Connection
Many reading this realize that an increase in intestinal permeability (also known as a leaky gut) can lead to the development of an autoimmune condition such as Graves’ Disease and Hashimoto’s Thyroiditis. Well, there is evidence that a vitamin D deficiency can lead to an increase in intestinal permeability. A study from 2008 showed that the vitamin D receptor plays a critical role in mucosal barrier homeostasis by preserving the integrity of the intestinal mucosal barrier (4). More recent studies have confirmed this, as a journal article from 2011 showed that the vitamin D pathway might play an important role in gut homeostasis and in signaling between the microbiota and the host (5). A couple of other studies from 2013 looked at the role of the vitamin D receptor in colitis, and showed that gut epithelial vitamin D receptor signaling inhibits colitis by protecting the mucosal epithelial barrier (6) (7). As a result, anyone who wants to have a healthy gut needs to have normal levels of vitamin D, and preferably levels well above the commonly used reference ranges.
Is Vitamin D Supplementation Necessary?
Most people reading this know that regular sun exposure is important for healthy vitamin D levels. As a result, if someone has a vitamin D deficiency, it’s normal to wonder whether getting sun exposure on a daily basis will be sufficient to raise the vitamin D levels. If a patient of mine has low or depressed levels of vitamin D I will almost always have them supplement with vitamin D3. And there are a few reasons for this:
1) Most people simply don’t get enough sun exposure. I’m guilty of this as well, as during the week I don’t get enough sun exposure, and as a result I supplement with vitamin D3 on a daily basis. But what you need to understand is that while you don’t need to tan your skin in order to synthesize vitamin D, if most of your skin isn’t exposed then this will affect the amount of vitamin D produced. In other words, the more skin that is exposed, the more vitamin D is produced (8). The reason I bring this up is because many people will take a walk outside for 30 minutes or longer each day and as a result feel as if they’re vitamin D levels are adequate. But if most of their body is covered during this time then they won’t get sufficient sun exposure.
2) Sometimes getting sufficient sun exposure won’t raise the vitamin D levels. Just getting older will have an impact, as the older you get, the less vitamin D your body produces. Latitude and season affect the synthesis of vitamin D3 (9). Air pollution can also be a factor, as while one can’t escape toxins, if you live in an area where there is a high amount of air pollution then this can affect the production of vitamin D (10) (11). So even if you are sunbathing on a daily basis there is a chance that you don’t have healthy levels of vitamin D due to other factors you can’t control. Of course the only way to confirm this is through proper testing.
3) The goal should be to raise the vitamin D levels as quick as possible. Even if someone can get their vitamin D levels to 50 ng/mL through sun exposure, it can take awhile to accomplish this. And so while I think it’s important to get daily sun exposure if possible, in many cases the quickest way to increase one’s vitamin D levels is by supplementing with vitamin D3. Of course there are circumstances when it can be dangerous to take high doses of vitamin D3, such as if someone has hypercalcemia. Since vitamin D3 increases the absorption of calcium, if someone has elevated serum calcium levels then it probably isn’t a good idea to supplement with high doses of vitamin D3.
Keep in mind that I’m not suggesting that everyone needs to supplement with vitamin D. Most children and young adults can maintain healthy vitamin D levels by getting 15 to 20 minutes of sun exposure a few days per week. On the other hand, if someone with an autoimmune thyroid condition has a vitamin D deficiency then in my opinion it is best to correct this deficiency through vitamin D supplementation. Then perhaps once this has been corrected they can maintain healthy levels through regular sun exposure.
In summary, although a vitamin D deficiency is a concern for medical doctors due to its role in bone health, most doctors don’t realize the importance of vitamin D in immune system health. There is a correlation between vitamin D levels and autoimmunity, and while a vitamin D deficiency itself might not cause an autoimmune condition, a deficiency in this important vitamin very well might make someone more susceptible to developing an autoimmune thyroid disorder such as Graves’ Disease or Hashimoto’s Thyroiditis. Although getting regular sun exposure can help to increase and maintaining healthy vitamin D levels, the quickest way to correct a deficiency is through supplementation.