If you’re living with celiac disease and following a gluten-free diet, you’ve already taken the most important step toward supporting your health. But here’s something that often gets overlooked: the gluten-free diet alone may not address all the nutritional gaps that celiac disease can create.
Supplements play a supporting role in any wellness plan. They’re meant to plug holes and fill deficiencies—to reinforce what you’re already doing with diet and lifestyle. And when it comes to celiac disease, vitamin D stands out as one of the most important nutrients to monitor.
Why? Because vitamin D deficiency is remarkably common in celiac disease, affecting anywhere from 25% to over 60% of people with the condition, depending on the study. And this deficiency may influence two of the key challenges people with celiac disease face: gut barrier integrity and immune system regulation.
Let’s explore what the research tells us about vitamin D and why it deserves a closer look if you’re managing celiac disease.
What Makes Vitamin D Different from Other Vitamins?
Most vitamins come from outside sources like food. Vitamin D is different—our bodies actually produce it.
What’s even more interesting is that vitamin D isn’t really a “vitamin” in the traditional sense. It’s actually a secosteroid, a hormonal precursor similar to steroids like cortisol, testosterone, and cholesterol.
Here’s how it works: When UVB light from the sun hits your skin, it interacts with a form of cholesterol called 7-dehydrocholesterol, and vitamin D3 (cholecalciferol) is created. But the process doesn’t stop there. Vitamin D3 still has to travel through your liver and kidneys to become the activated form your body can use, called calcitriol.
Once activated, calcitriol can bind to vitamin D receptors (VDRs) located in virtually every tissue in the body. Research indicates that vitamin D is involved in regulating more than 900 genes—affecting everything from brain function and cardiovascular health to immune support and bone mineralization.
This broad influence helps explain why vitamin D status matters so much for overall health. Its roles include:
- Supporting calcium absorption and bone health
- Modulating immune system function
- Playing a role in cell proliferation and differentiation
- Influencing gene expression across multiple body systems
Why Vitamin D Status Matters for People with Celiac Disease
Research consistently shows that vitamin D deficiency is common in people with celiac disease and occurs in both autoimmune conditions and inflammatory bowel conditions.
A 2021 case-control study in the Journal of Pediatrics found that children with celiac disease at diagnosis had significantly lower vitamin D levels compared to healthy controls (25.3 ng/mL vs. 31.6 ng/mL). The percentage with vitamin D deficiency (<20 ng/mL) was nearly three times higher in the celiac group: 31% versus 12%.
A 2024 systematic review and meta-analysis confirmed these findings, showing that vitamin D deficiency is more prevalent in pediatric celiac patients compared to healthy controls, with an odds ratio of 2.20.
In adults, a study of 530 celiac disease patients found that 25% had vitamin D deficiency, with another 34% having insufficient levels. That means nearly 60% of the celiac patients in this study had suboptimal vitamin D status.
This is particularly important if you’ve been prescribed corticosteroids like Prednisone. Research suggests these medications may interfere with vitamin D utilization, which can affect bone health over time.
Vitamin D and Gut Barrier Function
One of the most fascinating areas of vitamin D research relates to intestinal barrier integrity—what’s commonly called “leaky gut.”
The tight junctions in your small intestine contain adhesion junctions that help regulate what gets absorbed and what stays out. Dr. Tom O’Bryan has described these like a “rubber band” wrapped around the tight junctions—when they’re healthy, they snap back into place. When they’re compromised, they can lose their elasticity.
Research suggests that the vitamin D receptor (VDR) plays an important role in maintaining intestinal barrier function. The VDR is a transcription factor that regulates genes for several tight junction proteins, including claudin-2, claudin-5, claudin-12, and claudin-15.
A 2014 study in The Journal of Infectious Diseases found that vitamin D deficiency was associated with increased intestinal permeability and more severe colonic injury in an animal model. The researchers concluded that vitamin D is an important mediator of intestinal epithelial defenses.
Another study published in the American Journal of Physiology demonstrated that mice lacking the vitamin D receptor were much more susceptible to mucosal injury. In cell cultures, active vitamin D enhanced tight junction formation and increased the expression of junction proteins like ZO-1 and claudin-1.
For those with celiac disease, where supporting gut barrier function is a key consideration, these findings are particularly relevant.
Vitamin D and Immune System Regulation
The immune system relies on vitamin D for proper regulation. When you’re deficient, the body’s inflammatory response may be less effectively modulated.
Research published in the Journal of Investigative Medicine explains that vitamin D has extensive effects on immune cells:
- It suppresses T cell proliferation
- It promotes a shift from a Th1 (pro-inflammatory) to Th2 (anti-inflammatory) response
- It affects T cell maturation, promoting regulatory T cells while dampening the Th17 inflammatory phenotype
- It inhibits B cell proliferation and immunoglobulin secretion
A 2016 randomized controlled trial found that vitamin D supplementation modulated T cell-mediated immunity in humans, with changes observed in peripheral blood mononuclear cell gene expression.
Additional research indicates that the active form of vitamin D (1,25D) reduces the secretion of Th1-type inflammatory cytokines like IL-2, IFN-γ, and TNF-α, while promoting Th2-type anti-inflammatory cytokines like IL-4, IL-5, and IL-10.
For people with celiac disease—an autoimmune condition involving the gut and immune system—these immunomodulatory properties are worth understanding.
Vitamin D and Bone Health in Celiac Disease
One of the most well-established concerns for people with celiac disease is bone health. The malabsorption that occurs with intestinal damage can affect calcium and vitamin D absorption, potentially impacting bone mineral density over time.
The statistics here are significant:
- A review in Nutrición Hospitalaria found that low bone mineral density affects up to 75% of celiac patients
- A 2023 Danish nationwide cohort study found that celiac disease patients had a hazard ratio of 5.39 for developing osteoporosis compared to matched controls
- Research suggests that 18-35% of celiac patients have osteoporosis, with bone abnormalities being quite common
- A North American study found osteoporosis present in 34% of celiac patients at the lumbar spine, 27% at the femoral neck, and 36% at the radius
The direct effect on bones in celiac disease appears to be secondary to reduced absorption of calcium and vitamin D, which can lead to secondary hyperparathyroidism and subsequent effects on bone density.
This is why bone mineral density testing is often recommended at celiac disease diagnosis, particularly in adults, with follow-up testing based on initial results and gluten-free diet adherence.
How to Check Your Vitamin D Status
The first step to understanding your vitamin D needs is to check your current levels. This is done through a vitamin D, 25 Hydroxy blood test that measures serum levels. It’s a common test that most doctors can order.
Different health authorities have varying recommendations for optimal serum levels:
- The Vitamin D Council recommends serum levels between 40-80 ng/mL
- Chris Kresser has recommended serum levels between 35-50 ng/mL
- Mark Sisson has recommended serum levels between 50-60 ng/mL
- The Endocrine Society suggests levels above 30 ng/mL to avoid deficiency
If your levels are low, working with your healthcare provider to develop a supplementation strategy makes sense.
Getting Vitamin D: Sun Exposure and Supplementation
The Sun: Nature’s Vitamin D Source
The most natural way to get vitamin D is from the sun. Depending on factors like your location, skin tone, and the time of year, about 20-30 minutes of midday sun exposure with significant skin exposed may help support vitamin D production.
However, many factors can limit sun-derived vitamin D:
- Living at northern latitudes
- Having darker skin pigmentation
- Spending most time indoors
- Using sunscreen (which is still important for skin health)
- The season (winter months provide less UVB)
For many people, especially those with celiac disease who may have absorption challenges, supplementation becomes an important consideration.
Vitamin D Supplementation Considerations
The amount of vitamin D each person needs is highly individual. It depends on current serum levels, sun exposure, absorption capacity, body weight, and other factors.
Various recommendations exist:
- The Vitamin D Council has suggested a minimum of 1,000 IU per 25 pounds of body weight, with adults and adolescents taking at least 5,000 IUs a day in the absence of adequate sun exposure
- Chris Kresser has recommended between 2,000-5,000 IUs daily to maintain serum levels in his suggested range
- Mark Sisson has recommended 4,000 IUs daily to maintain serum levels in his suggested range
For people with significant deficiency, some research has explored higher short-term doses. A study on celiac disease patients with acute vitamin D deficiency found that supplementation with 50,000 IUs 1-3 times per week (under medical supervision) was used until gut health improved and proper vitamin D levels were restored.
Important: Higher-dose supplementation should only be done under the guidance of a healthcare provider who can monitor your serum levels. Vitamin D is fat-soluble and can accumulate in the body.
No matter how much you decide to supplement, it’s important to keep getting your serum blood levels tested regularly to fine-tune the amount you’re taking. Your needs will change based on the time of year, what you’re eating, stress levels, and how well you’re absorbing nutrients.
Supporting Your Overall Gut Health
Vitamin D is one piece of a larger puzzle. For people with celiac disease, a comprehensive approach includes:
- Strict adherence to a gluten-free diet — This remains the foundation of celiac disease management
- Addressing nutrient deficiencies — Beyond vitamin D, people with celiac disease may benefit from monitoring iron, B12, folate, calcium, and other nutrients that can be affected by malabsorption
- Supporting gut barrier function — Some people choose to support their gut health with nutrients like L-glutamine, which research suggests may help support intestinal tissue health
- Working with healthcare providers — Regular monitoring, including follow-up antibody testing and potentially repeat biopsies or bone density scans, helps track progress
- Digestive support — Some individuals find that digestive enzymes help support nutrient breakdown and absorption during the healing process
The goal is to create an environment where your gut can function optimally and your body has the nutritional support it needs.
Frequently Asked Questions
Why is vitamin D deficiency so common in celiac disease?
Several factors contribute. The intestinal damage in celiac disease can impair absorption of fat-soluble vitamins like vitamin D. Additionally, inflammation may affect vitamin D metabolism, and many people with celiac disease may not yet be eating a diet that optimally supports their nutritional needs.
How often should I test my vitamin D levels?
Most practitioners recommend testing at diagnosis, then again after 3-6 months of supplementation to assess response. Once levels are stable and in the optimal range, annual testing may be sufficient. Your healthcare provider can recommend a schedule based on your individual situation.
Can I get enough vitamin D from food alone?
For most people, especially those with celiac disease, food sources alone are unlikely to provide optimal vitamin D levels. While fatty fish, egg yolks, and fortified foods contain some vitamin D, the amounts are relatively small compared to what the body can produce from sun exposure or obtain through supplementation.
Should I take vitamin D with food?
Vitamin D is fat-soluble, so taking it with a meal containing some fat may help with absorption. This is particularly relevant for people with celiac disease who may have compromised fat absorption.
What form of vitamin D should I take?
Vitamin D3 (cholecalciferol) is generally considered more effective at raising and maintaining serum vitamin D levels than vitamin D2 (ergocalciferol). Most supplements use D3, which is the same form your body produces from sun exposure.
Can vitamin D levels improve after going gluten-free?
Research suggests that vitamin D status can improve after following a strict gluten-free diet, likely because intestinal healing improves absorption. A longitudinal study found that vitamin D deficiency prevalence decreased from 68% at baseline to 8% after 5 years on a gluten-free diet. However, supplementation may still be helpful, especially in the early stages of healing.
Key Takeaways
- Vitamin D deficiency is common in celiac disease, with studies showing 25-60%+ of patients have low or insufficient levels
- Vitamin D supports gut barrier function by helping regulate tight junction proteins in the intestinal lining
- The vitamin D receptor influences immune function, helping modulate inflammatory responses and T cell activity
- Bone health is a significant concern in celiac disease, with up to 75% of patients showing low bone mineral density
- Testing is essential — a 25-Hydroxy vitamin D blood test reveals your current status and helps guide supplementation
- Individualized supplementation under healthcare provider guidance can help achieve and maintain optimal levels
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