There’s a lot to consider when it comes to vitamin D | 9 min read
Our Founder, Luca, enjoying the sun with Ziggy.
Key takeaways from this post
Sources of vitamin D include diet, supplements, and exposure to ultraviolet-B (UVB) rays from the sun.
Vitamin D is a key contributor to healthy immune responses, such as intestinal innate immunity.
Innate immunity is affected by Crohn’s disease and low vitamin D levels, suggesting a possible link between these factors.
Several studies have evaluated the role of vitamin D in diagnosis, disease activity, and quality of life in Crohn’s disease patients.
Experts suggest a link between vitamin D and COVID-19 - see how Crohn’s disease fits into this.
How can one vitamin have such an impact on so many bodily processes, including gastrointestinal issues? Well, for starters, vitamin D technically isn’t even in a vitamin in the way that others are, like vitamin A or B12. The term “vitamin” refers to a molecule and essential nutrient needed in small amounts for biological functions and that our bodies can’t produce on their own. Vitamin D is a bit different because along with getting it from supplements or in small amounts from some foods such as milk, it can be made when UVB rays come in contact with the skin. It’s quite a complicated, but important, process.
To understand the value of vitamin D and why it matters so much for people with Crohn’s disease, let’s first discuss some basic biology.
How can sunlight possibly make a vitamin?
In some regions of the world, particularly at higher latitudes, UVB radiation is captured before it reaches the earth, so our bodies tend to lack adequate sun exposure. This is known as “vitamin D winter”, when vitamin D may not be produced enough because of limited UVB contact with the skin. Without getting it from diet or supplements, many people become deficient in vitamin D during these periods.
When UVB rays from the sun hit the skin, a compound called 7-dehydrocholesterol is created and then processed into vitamin D3. From here, vitamin D3 from the skin is met in the circulation by vitamin D3 coming from the diet and absorbed in the intestinal tract. It is further processed by the liver and kidneys to produce 1α,25-dihydroxyvitamin D3, the active form of vitamin D, but scientists prefer to just call it 1,25D. It may be a short nickname, but this important molecule has a large array of functions throughout the body!
What makes vitamin D so important?
From bone health to fighting COVID-19, vitamin D is very popular. Its role in the immune system is varied and complex, but to put a few examples simply, it can inhibit inflammation and help regulate immune responses. To illustrate this point, evidence suggests that vitamin D helps protect the intestinal lining, which is the thin, but vital, layer that separates the gut microbiome from the rest of the body. Vitamin D is part of the process of regulating this intestinal barrier, allowing it to function optimally. When the intestinal barrier is compromised, immune reactions and inflammation are likely to occur because bacteria, fungi, and whatever else can travel into (or out of) the intestines and trigger a response.
Let’s discuss another major role that vitamin D plays in immune activity. Innate immunity, which is the automatic response of immune cells against threats to the body such as infections, requires signals from 1,25D to optimally detect and respond to foreign invaders in the body. In the past, it was thought that vitamin D deficiency occurred because of Crohn’s disease. The idea was that patients aren’t absorbing the vitamin properly in the intestines from dietary sources or don’t get enough UVB exposure, linking active Crohn’s disease to people living in regions that receive less UVB rays. This relates to vitamin D winter, which many experience in these areas, affecting their vitamin D levels. Now, however, there’s a growing body of research pointing to vitamin D deficiency as a trigger for Crohn’s disease as well as the role of vitamin D supplements in improving innate immune responses, preventing inflammation and symptoms.
The innate immune system is also related to the microbiome. Vitamin D helps prevent intestinal inflammation because it has a role in mediating innate immunity, which regulates microbial activity. When paired with the notion that Crohn’s disease is defined by problems with intestinal innate immune responses, there’s a lot to discuss.
A healthy microbiome also depends on different types of proteins in order to function optimally. Proteins are very important structures made of amino acids that perform a wide variety of functions throughout the body. For a healthy microbiome, proteins with antimicrobial properties are an important part of the equation. However, research has shown that vitamin D deficiency affects levels of these proteins, leading to variability in gut bacteria. A lack of balance in the gut microbiome, known as dysbiosis, is characteristic of Crohn’s disease development and generally considered problematic for gut, physical, and mental health. Some examples of genes that promote antibacterial activity with the support of vitamin D are NOD2, DEFB4/HBD2, and angiogenin-4. Genetic mutations (glitches that affect how someone’s genes work) in the NOD2 gene have long been linked to Crohn’s disease. Scientists suggest that 1,25D can help prevent Crohn’s because it influences how much NOD2 is released. Overall, vitamin D has an impact on the composition, diversity, and function of intestinal bacteria (1,2,3).
To better understand this complex interaction, let’s dive deeper into the relationship between vitamin D and Crohn’s disease by investigating some clinical studies.
A 22-year study of 72,719 women assessed the risk of developing Crohn’s disease based on levels of 25D, which is an earlier version of 1,25D before it has been processed into the active form of vitamin D. They found that higher predicted levels of 25D before diagnosis led to a significantly lower risk of developing Crohn’s disease later. Predicted levels of vitamin D were determined using information such as intake of vitamin D through dietary sources and supplementation, sun exposure, race, body mass index, and regional intensity of UVB radiation (4).
Another study of 403 Crohn’s patients found a pattern of vitamin D deficiency, which was independently linked to both worse health-related quality of life and more disease activity. For instance, patients deficient in vitamin D had significantly lower scores on the Short Inflammatory Bowel Disease Questionnaire, which helps evaluate quality of life (5).
Furthermore, among children with inflammatory bowel diseases including Crohn’s disease, a strong relationship was found between vitamin D supplement intake, blood levels of 25D, and a lack of disease activity. Throughout the study of 505 pediatric patients followed between 2007 and 2010, 17% of patients achieved clinical remission. This was done in part with proper use and monitoring of vitamin D supplementation (6).
In yet another study, the consequences of low vitamin D levels were studied. Among over 1500 patients with Crohn’s disease, those with low 25D levels were more likely to have surgery and be hospitalized due to their disease, compared to those who had higher amounts of 25D in their bodies. Interestingly, taking vitamin D supplements to counteract the low levels among these patients better helped to prevent surgery than those who did not supplement to improve their vitamin D levels (7).
Lastly, a recent report has shown that seven weeks of high-dose vitamin D treatment helped patients in two ways: it limited the need for escalating doses of infliximab, a common drug for Crohn’s disease patients, and it had an anti-inflammatory effect. However, more research must be done to figure out healthy doses for each patient. Links to genetic factors and the gut microbiome should be studied further as well (8).
Overall, there’s lots of research to suggest that vitamin D deficiency is bad news for Crohn’s disease patients and that healthier levels of the vitamin promote better health outcomes. When it comes to COVID-19, this role cannot be understated.
Vitamin D and COVID-19
We’ve already discussed the role of vitamin D in the immune system. When it comes to the novel coronavirus, the immune system certainly needs to be in fighting form. Emerging research suggests that vitamin D may be linked to a lower likelihood of coming down with COVID. With staggering figures of vitamin D deficiency such as 1 billion people around the world, 35% of American adults, and upwards of 80% of adults in Pakistan, Bangladesh, and India, the link between vitamin D and COVID-19 could be an important one (9,10).
SARS-CoV2 affects the innate immune system, which, if we recall from earlier, is already dysfunctional in people with Crohn’s disease. Putting all the pieces together, it’s by no means a stretch to suggest that people with Crohn’s disease may be at higher risk of developing SARS-CoV2 and having a more severe case of it, even solely based on low vitamin D levels exhibited among many Crohn’s patients and their defective intestinal immune activity.
What does all this mean for Crohn’s patients?
Considering vitamin D regulates the gut’s immune response and Crohn’s partially arises from defective intestinal immunity, it makes sense why scientists are exploring the connection. This is encouraging for Crohn’s disease patients, their loved ones, and advocates because we could have more definitive answers to our questions about how vitamin D is related to Crohn’s and other inflammatory bowel diseases.
For now, the current evidence that sufficient vitamin D levels are beneficial to Crohn’s patients is good news because vitamin D is an inexpensive supplement with few side effects. This means that if it can help someone with Crohn’s, there’s nothing really standing in their way from taking supplements, or even getting some extra sunlight and eating vitamin D-rich foods such as fatty fish.
It’s important to speak to a doctor about supplementing with vitamin D to do it optimally and safely. If you have Crohn’s disease or believe you may be genetically predisposed to developing it, it’s worth consulting healthcare professionals and requesting a test to determine the levels of vitamin D in your blood.
If you’re going to be supplementing with or increasing your dietary intake of vitamin D, you’ll have one more reason to use the Phyla app. On the app, you can track your supplement usage and diet, and see how it affects your gut health over time. Armed with this data, you’ll know first-hand what’s working for you and what isn’t . This is just one way the Phyla app helps empower you to make decisions about what’s right for you.