Vitamin B12

Reviewed by: HU Medical Review Board | Last reviewed: August 2023

Inflammatory bowel disease (IBD) is a condition in which chronic inflammation in the digestive tract can cause a range of different symptoms and complications, depending on where in the digestive tract the inflammation is located. The two main forms of IBD are Crohn’s disease (CD) and ulcerative colitis (UC). UC can affect the colon (large intestine) and rectum, and CD can cause inflammation and damage anywhere along the digestive tract from the mouth to the anus.

The primary role of the digestive system is to absorb nutrients from the food that a person eats, so that the nutrients can be transformed into energy that fuels all of the other important processes in the body. The digestive process mainly occurs in the small intestine. While either form of IBD can affect how a person’s digestive system absorbs important nutrients from food, this is particularly a concern for people with CD. For this reason, people with CD are monitored by healthcare providers to make sure that their bodies have enough of these essential nutrients, including one called vitamin B12.1

What is vitamin B12?

Vitamin B12 is an essential part of what is called the B-vitamin complex. This complex includes eight vitamins, which are nutrients that play an important part in the body’s ability to convert food into energy. Vitamin B12 is “water soluble.” This means that it disintegrates in water, causing any excess amount of the vitamin to be expelled through the urine. Vitamin B12 is found in common foods such as fish, meat, eggs and dairy products.2

How is vitamin B12 related to inflammatory bowel disease?

Vitamins are absorbed from food during the digestion process. Vitamin B12, specifically, is absorbed by the lower part of the small intestine (called the ileum). For people with CD that affects the ileum, also referred to as ileitis, their small intestines may not be able to absorb enough vitamin B12, which is called a “vitamin B12 deficiency.” Patients who have undergone small bowel surgery may be more likely to develop a vitamin B12 deficiency. People with CD will usually undergo routine blood tests to make sure they have not developed any vitamin deficiencies.1,2

What are some signs of vitamin B12 deficiency?

Having vitamin B12 deficiency can cause a range of different kinds of symptoms in different people. Some possible symptoms that are related to the digestive tract include:3

  • Tongue soreness
  • Loss of appetite
  • Constipation

Vitamin B12 deficiency can also cause symptoms that are not related to the digestive tract. These may include:3

  • Memory loss
  • Feeling disoriented
  • Numbness or tingling of hands and feet
  • Fatigue
  • Paranoia

What are vitamin B12 supplements?

If blood tests indicate that a person has vitamin B12 deficiency, a healthcare provider may recommend taking a vitamin B12 supplement. Vitamin B12 is found in most animal food products, where it is bound to proteins. When this type of food is digested, bacteria in the intestine work to release the vitamin from the protein, which is then absorbed by the small intestine.2,3

If a person’s small intestine is not absorbing enough food-bound vitamin B12, causing a deficiency, there are ways to supplement B12 intake. Over-the-counter oral forms of vitamin B12 are available at most drug stores and health food stores. They can be bought as a single-nutrient B12 supplement or as a complete B-complex supplement. While this is a good option for some people, oral supplementation of B12 may not work well enough for some patients with CD. For those patients, a healthcare provider may advise them to take vitamin B12 as an injection or nasal spray, which are only available with a prescription. In some cases, an IV (intravenous) preparation may be necessary, which would be administered by a healthcare professional.2,3

Vitamin B12 supplementation has shown to be very safe even at high doses with little to no side effects. However, some drugs taken at the same time as vitamin B12 supplements will reduce the body’s ability to absorb enough of the vitamin B12. As with any supplementation, it is always important to talk with your doctor about potential interactions with other drugs.2,3

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