IBD and Vitamin D Levels

Crohn's disease or ulcerative colitis is a risk for a deficiency

A man wearing a baseball cap and glasses with his eyes closed, enjoying sunlight on his face.

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Having inflammatory bowel disease (IBD) puts one at risk of certain vitamin deficiencies. Which vitamins, the extent of the deficiency, and how to improve the vitamin levels are all going to be different for each patient.

Many people with IBD have their vitamin levels monitored on a regular basis but others do not, and therefore may not know of vitamin deficiencies. Having Crohn's disease, ulcerative colitis, or indeterminate colitis increases the risk of not having enough vitamin D.

About Vitamin D

Vitamin D can be gotten through eating some foods. However, it is also known as the "sunshine vitamin." This is because it is synthesized (created) by the body when the skin is exposed to sunlight. For people who don't have sun exposure because of where they live or because they don't spend much time outside in the sun, vitamin D levels may be lower.

Vitamin D plays an important role in bone growth. Calcium is also important in maintaining the health of bones. Vitamin D is the helper vitamin for calcium. A lack of vitamin D leads to a reduction in the amount of calcium that can be used by the body.

People with IBD are also at increased risk of having bone disease such as osteoporosis. This ultimately all puts people with IBD more likely to have bone fractures.

Why People With IBD May Lack Vitamin D

There are several reasons why people who live with IBD may have a lack of vitamin D.

Fat Absorption

In order for vitamin D to be absorbed and used effectively by the body, there must be some dietary fat. Fat is absorbed in the small intestine. Some forms of Crohn's disease cause inflammation in the small intestine.

Having this active small intestine inflammation may decrease the absorption of fat. Because fat is needed to absorb vitamin D, this can cause less vitamin D to be absorbed.

Lack of Sunlight

For some people with IBD, especially during a flare-up, time outside in the sun may be limited. After all, being outdoors and away from a bathroom can be challenging at times for those who are having symptoms like diarrhea.

For those who live in northern climates, there is a shorter part of the year where it's easy to get sunlight outdoors. Additionally, people with IBD are known to have an increased risk of skin cancer. That may also keep some people with IBD out of the sunlight which can help increase vitamin D levels.

Surgery

People with IBD, and Crohn's disease in particular, often have surgery on their bowels. When the surgery is done on the last part of the small intestine (the terminal ileum), it can affect the absorption of vitamin D. Resections in the large bowel have not shown the same risk of low vitamin D.

Disease Activity

Having active disease could lead to lower levels of vitamin D. Especially with ulcerative colitis, patients with lower vitamin D levels had more active disease. People with active Crohn's disease didn't show the same link to having low vitamin D levels.

The authors of one study note that this could be helpful for monitoring disease activity in ulcerative colitis. It could be that lower vitamin D levels are a signal that the ulcerative colitis is becoming more active.

Corticosteroids

Medications called corticosteroids (which include prednisone) are often used to treat IBD. The goal is to use these drugs sparingly and for the shortest amount of time possible.

However, some people receive these drugs for long periods of time or on and off to cope with flare-ups. However, the use of these drugs is also connected to lower vitamin D levels in people with IBD.

Darker Skin

People with darker skin (such as those of African descent) are known to be at greater risk of vitamin D deficiencies. This is because for dark skin, more sun exposure is needed to create vitamin D.

One study included 237 patients, 43% of whom were Black. The authors found that Black patients were more likely to have vitamin D deficiency. Doctors who treat IBD patients with darker skin will want to make sure levels are being tested regularly.

Which Came First: IBD or Vitamin D Deficiency?

It's known that vitamin D deficiency is common in people who live with IBD. That has led to the question as to whether the lack of vitamin D actually contributes to the development of IBD. There are some studies that show that the lack of vitamin D could increase the risk of having IBD.

It could be that this is a relationship that one researcher calls "bidirectional." In other words, IBD causes people to have low levels of vitamin D. Then the low levels of vitamin D might increase the risk of an immune response. The immune response can lead to either a flare-up of IBD or in developing a form of IBD in the first place.

Health Maintenance in IBD

For people with IBD, there are regular "health maintenance" items that need to be completed every so often. Most people with IBD know that this includes tests like colonoscopy to check inflammation. However, regular testing should also be done to assess vitamin levels.

Vitamin D is one of the vitamins that should be checked every so often. In most cases, this means checking vitamin D levels at least yearly. When levels are found to be low and there's a need to add a supplement, it may be necessary to check them again after several weeks. 

Vitamin D Supplementation

Supplementing with vitamin D should be done with the help of a physician. If vitamin D levels are not found to be low, supplements aren't usually recommended. When vitamin D is supplemented, it may also be necessary to supplement with calcium as well.

There is a lack of evidence about how much vitamin D IBD patients should receive. This is because most studies and recommendations about vitamin D are done on healthy people who don't live with bowel disease. However, one study showed that a dose between 1800 IU and 10,000 IU daily might be needed.

In many cases it might not be possible to increase vitamin D levels or maintain them through diet. However, vitamin D can be found in these food sources:

  • Butter and fortified margarines
  • Eggs
  • Fish liver oils
  • Fortified milk and milk powder
  • Liver
  • Some fortified cereals

A Word From Verywell

People in the IBD community often talk about how having this disease is like having a full-time job. Vitamin D levels are one more item that people who live with IBD need to watch. And because vitamin D doesn't do its work alone, calcium is also a priority for people who have IBD.

It can be frustrating to add one more thing to the list of labs and blood work that must be done. However, vitamin D levels are something that need to be taken care of over the long term. It takes time for vitamin D levels to be raised up once they get low. This is especially true for those that have problems absorbing vitamin D in the first place.

Living in an area that doesn't receive sunlight all year round makes it more challenging to get enough vitamin D. Taking a supplement might be necessary.

A gastroenterologist or other physician such as a primary care physician should be ordering a blood test to check vitamin D levels at regular intervals (likely yearly). If needed, a doctor should also be making a recommendation about vitamin D supplements.

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