Low Vitamin D And IBS | Is There A Powerful Connection?
Written By Kobi Nathan, Pharm.D., M.Ed., CDP, BCGP, AGSF
Sleep Disorders
July 28, 2023

Low Vitamin D and IBS

Research and clinical evidence suggest that there is a relationship between low vitamin D and IBS (irritable bowel syndrome).

Watch the video below from a physician who describes the relationship between low Vitamin D and IBS:

Vitamin D, sometimes known as calciferol, is an important type of vitamin involved in mineral metabolism and bone development.

It is present in foods such as fish, red meat, and eggs and is also available through supplementation.

Vitamin D is also synthesized in the skin when exposed to ultraviolet (UV) rays from the sunlight.

Vitamin D plays a role in calcium absorption and maintaining appropriate calcium and phosphate concentrations in the blood.

These levels are important to sustain as they contribute to bone growth and strength.

Certain conditions like osteoporosis and rickets involve underlying vitamin D deficiencies.

Vitamin D has many other roles within the body. Vitamin D affects inflammation, blood sugar regulation, nerve and muscle function, hormone secretion, and immune system activity.

The Translational Cancer Research website suggests low vitamin D levels may be a risk factor for non-small cell lung cancer.

Cell growth and death are also regulated by vitamin D.

This article will discuss the many advantages of vitamin D supplementation, particularly the benefits in mitigating symptoms of IBS.

Before we get into the relationship between Vitamin D and IBS, we must review what Vitamin D is and how it works in the body.

Let’s get into it…

What is vitamin D’s mechanism of action (How does it work)?

Vitamin D binds to a receptor inside human cells called the vitamin D receptor (VDR).

After binding vitamin D, the VDR attaches to another receptor called the retinoid-X receptor.

This forms an important complex that binds to DNA and makes protein.

What is the relationship between vitamin D and calcium?

Calcium plays a role in building and maintaining bone health.

Vitamin D regulates calcium levels by adjusting the absorption of calcium.

Those with low vitamin D levels do not produce sufficient amounts of calcitriol (the “active” form of vitamin D), leading to decreased calcium absorption from food.

The body will compensate by taking calcium from existing bone stores, thus weakening bones and preventing the formation of new, strong bones.

Because calcium and vitamin D work together, it is necessary to have a sufficient intake of both to sustain good bone and overall health.

How do you test for vitamin D levels?

Several reports and clinical trials have linked decreased vitamin D levels to cancer, heart disease, diabetes, and many other illnesses, causing many physicians to initiate routine testing of vitamin D levels in patients.

To determine this, providers will run a vitamin D blood test, also called a 25(OH)D level.

However, taking an appropriate daily dose of vitamin D will likely get one’s levels within the desired range.

Additionally, a review of 25 vitamin D studies concluded that knowing a healthy patient’s vitamin D level is not overly useful.

Therefore, the American Geriatrics Society (AGS) has stated that frequent blood tests are unnecessary in most cases.

However, regular testing may be useful for those with severe vitamin deficiency and specific conditions.

How do you take vitamin D?

The AGS suggests that older individuals take 1000 international units (IU) of vitamin D3 daily to prevent deficiencies and fractures.

It is important that individuals not take too much vitamin D, as this can pose its own risks.

One study demonstrated an increased incidence of falls and fractures in older adults on high doses of vitamin D (>500,000 IU per year).

Vitamin D is also closely linked to calcium, and too much vitamin D can increase calcium levels in the blood.

Therefore, the AGS recommends that doses not exceed 4,000 IU Vitamin D daily.

Some patients with severe deficiencies or certain diagnoses may require greater than 1,000 IU daily, and these patients should be prescribed supplementation and monitored by a doctor.

Why is it important to have sufficient vitamin D?

Though there are arguments against using vitamin D, there is evidence that vitamin D supplements can benefit older adults.

Each person’s vitamin D depends on various factors, including where one lives, lifestyle, time of day, season, or skin pigmentation.

For example, less sunlight might decrease vitamin D production during the colder months.

Additionally, as people age, they often do not get regular exposure to sunlight and have difficulty absorbing vitamin D into their skin.

For this reason, older adults are often deficient in vitamin D and require some supplementation.

Various advantages of adequate vitamin D intake may include:

  • Supporting bone health in those suffering from osteoporosis.
  • Maintenance of immune response.
  • Improving muscle health and function to decrease the risk of falls and fractures.
  • Alleviating the painful symptoms of inflammatory bowel disease.

The role of vitamin D is also being studied in other disease states.

Though evidence is inconclusive at this time, vitamin D could also have potential benefits in:

  • Improving poor cognition associated with vitamin D deficiency.
  • Reducing the risk of cancer.
  • Maintaining gut health.
  • Decreasing the risk of developing multiple sclerosis (MS).
  • Treating psoriasis through topical application.
  • Treating and preventing other bone disorders, such as osteomalacia (softening of the bones) and rickets.

What are the potential side effects associated with vitamin D?

When taken at an appropriate dose, vitamin D supplementation is considered safe.

However, if one were to exceed the recommended 4,000 IU of vitamin D Daily, they might experience more serious side effects such as:

  • Nausea and vomiting.
  • Constipation.
  • Poor appetite and weight loss.
  • Confusion and disorientation.
  • Weakness.
  • Heart rhythm problems.
  • Kidney stones and kidney damage.

What is Irritable Bowel Syndrome (IBS)?

IBS is a chronic gastrointestinal disorder characterized by digestive symptoms such as recurrent abdominal pain, stomach cramps, bloating, gas, changes in bowel habits, diarrhea, and constipation.

These symptoms can be caused by diet and medication.

IBS patients also often have underlying mental health issues, like anxiety and depression, that can adversely affect symptom severity.

IBS can be uncomfortable and painful and often interfere with a patient’s quality of life.

While several remedies are available, there is no cure for this chronic condition.

Each individual patient is unique, and relief may require various interventions.

One of these potential interventions includes vitamin D.

How can vitamin D treat IBS?

The underlying bodily mechanisms that cause IBS are not entirely known.

However, those with IBS have a different gut microbiome, immune function, intestinal permeability, brain-gut relationship, and mental status.

It has been demonstrated that vitamin D can regulate all of these potential mechanisms underlying IBS.

Experts now think that vitamin D can play an important role in controlling the severity of IBS symptoms.

It is important to note that there is a high prevalence of vitamin D deficiency in IBS patients compared to non-IBS patients.

A case-control study analyzed vitamin D concentrations in the blood of IBS patients.

The average vitamin D concentration in patients with IBS was 21±12 nmol/L, significantly lower than the 31±16 nmol/L level reported in the non-IBS group.

This suggests that low vitamin D status may be characteristic of the disease.

Deficient vitamin D is associated with an increased risk of developing colorectal cancer and has a potential role in irritable bowel disease.

Various studies have evaluated the high incidence of vitamin D deficiency amongst IBS sufferers and the potential for relief with vitamin D supplementation.

One recent study, in particular, evaluated patients’ self-reported symptom severity and quality of life (QOL) after receiving 50,000 IU of vitamin D weekly for six weeks.

Results were overwhelmingly positive, with the vitamin D group demonstrating significant improvements in the severity of symptoms and QOL when compared to those receiving placebo.

So, should we definitely treat IBS with vitamin D?

Other experts disagree with current evidence and state that there have not been enough controlled trials studying this phenomenon.

Liz Williams, a nutrition professor at the University of Sheffield, has researched this area.

She concludes that vitamin D supplementation did not affect IBS symptom severity.

When studying 135 patients with IBS, half received vitamin D3, and the other half received a placebo for three months.

The results demonstrated no significant difference in symptom resolution between the two groups.

Though Williams sees a potential benefit for those with deficiencies, she does not concede with evidence supporting its use in IBS.

The long‑term effects of vitamin D on IBS definitely require further evaluation, and disagreement exists amongst the medical community on the benefits of supplementation.

Another study conducted by Bernard Corfe and colleagues also suggests that vitamin D supplementation in people with IBS does not affect alleviating symptom severity or improving quality of life.

Regardless, there is evidence supporting vitamin D for IBS relief and improving general health, and with proper dosage, there is very little risk when taking vitamin D.

Therefore, providers and patients should consider treating with vitamin D for IBS and beyond.

One trustworthy, credible supplement seller I recommend is  PerformanceLab.

Their products are lab-tested, research-backed, and manufactured in FDA-approved and GMP-certified facilities.

The company sells a 2-1 Vitamin D and K2 combination supplement:

Vitamin D and K2 nutrition label

If you want to buy their Vitamin K2 and D3 combination supplement, you can do so through their official website link here.

Finally, if you are taking any medication, it is always advisable to consult your doctor before starting any new dietary supplements, including those containing Vitamin K2 MK7, just to be safe.

To read more about the potential health benefits of Vitamin K2, read my article here.


Vitamin D has many positive health effects, including supporting bone health and preventing falls and fractures.

Therefore, it is recommended that older adults incorporate vitamin D supplementation at a safe dose of 1,000 mg daily into their medication regimens.

Aside from its known benefits, vitamin D may improve the severity of gastrointestinal symptoms in the IBS population.

Though further research is needed to confirm further advantages and long-term health, patients with poor vitamin D status can’t go wrong with proper vitamin D supplementation.

This article has an affiliate link. I may earn a small commission from purchases made through the link at no additional cost to you.


  1. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
  2. https://betterhealthwhileaging.net/vitamin-d-healthy-aging-dose-faqs/
  3. https://journals.physiology.org/doi/full/10.1152/physrev.00014.2015
  4. https://www.endocrineweb.com/conditions/osteoporosis/role-calcium-vitamin-d-bone-health#:~:text=Calcium%20and%20vitamin%20D%20work,re%20deficient%20in%20vitamin%20D.
  5. https://www.webmd.com/ibs/news/20210805/vitamin-d-wont-help-ease-irritable-bowel-syndrome-study
  6. https://www.health.harvard.edu/blog/vitamin-d-testing-recommended-people-201411267547
  7. https://pubmed.ncbi.nlm.nih.gov/28758188/
  8. https://pubmed.ncbi.nlm.nih.gov/24350602/
  9. https://pubmed.ncbi.nlm.nih.gov/26747333/

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