Share on Pinterest
Getty Images

If you live with Crohn’s disease or ulcerative colitis, you’re likely well acquainted with the gastrointestinal (GI) symptoms that inflammatory bowel disease (IBD) can cause.

Besides GI symptoms, people with IBD commonly experience nutritional deficiencies, with the three most common being iron deficiency, vitamin D deficiency, and vitamin B12 deficiency.

I’ve been living with Crohn’s disease for about 6 years now, so I understand firsthand what it’s like to live with nutritional deficiencies. It can certainly be hard to get these levels up to the ideal range.

It was not until I went to medical school that I really understood why these deficiencies occur and what to do about them.

The frequent bathroom visits, loss of appetite, and inflammation common in IBD can all contribute to malnutrition and decreased nutrient absorption.

Some people with these vitamin and mineral deficiencies have no symptoms, while others may experience some — like fatigue and cognitive issues — and report a decreased quality of life.

There can also be some dangers with ongoing nutritional deficiencies, which is why it’s important to identify which deficiencies you might have and appropriately treat them.

The body uses iron to make a protein called hemoglobin, which allows red blood cells to carry oxygen from the lungs to the rest of the body. The upper parts of the small intestine absorb iron.

The best sources of iron are in meat — especially red meat. There’s also iron in plants, such as leafy greens, but this form of iron is much more difficult for the body to absorb. This is why vegetarians are at higher risk of iron deficiency.

Anemia, or low hemoglobin levels, happens when the body cannot make enough healthy red blood cells. Iron deficiency anemia is very common in those with IBD, with an estimated two-thirds experiencing some form of anemia due to their disease.

It is possible to have iron deficiency without anemia.

Iron deficiency can happen with:

  • blood loss (commonly GI or menstrual)
  • decreased absorption (often due to inflammation in the small bowel)
  • decreased dietary intake of iron (vegetarian/vegan diets)

You could have chronic blood loss without even realizing it. Sometimes, you cannot see the blood in your stool without using a microscope.

Signs and symptoms of iron deficiency anemia include:

  • weakness
  • fatigue
  • shortness of breath
  • difficulty concentrating
  • restless legs
  • pale skin
  • fast heartbeat
  • pica, a condition in which individuals crave items that are not food, like ice or dirt

My sister always notices when I’m anemic, as my face has no color and my lips become especially pale. I also notice that I become much more exhausted climbing stairs, and I do not have the stamina or endurance to exercise like I normally can.

Treatment includes replenishing iron stores either orally or intravenously. Some people with IBD tolerate oral iron supplements well, and others experience exacerbated GI symptoms with oral iron, necessitating the use of intravenous iron.

However, if anemia is severe enough, a blood transfusion may be necessary to increase hemoglobin levels back to a healthy range.

Throughout the years, iron infusions, in addition to eating plenty of iron-rich foods, have helped maintain my iron levels and improve anemia.

Vitamin D is a steroid hormone our bodies produce from sunlight on our skin. It’s also found in some foods.

It can be difficult to obtain enough vitamin D from the sun alone, which is why many people require vitamin D supplements in addition to consuming vitamin D-rich foods.

Some of the best dietary sources of vitamin D include:

  • cod liver oil
  • salmon
  • tuna
  • dairy products
  • eggs

People with IBD have a higher chance of developing vitamin D deficiency due to malnutrition and malabsorption.

Low vitamin D levels are associated with an increased risk of hospitalizations and surgeries in people with IBD. On the other hand, higher vitamin D levels are associated with a decreased risk of Clostridioides difficile (C. diff) infection, which those of us with IBD are also at an increased risk for.

Most people with vitamin D deficiency have no symptoms.

Longer-term vitamin D and calcium deficiencies increase the chances of developing osteoporosis or decreased bone mineral density. This increases chances of fracturing bones.

Vitamin D deficiencies have also been associated with some cancers and autoimmune diseases. A deficiency is typically treated with oral vitamin D supplements.

My vitamin D levels are almost always low, so I try to be consistent about taking vitamin D supplements and getting out in the sun. This is hard now that I’m a resident physician and not a lifeguard anymore!

I can’t say I notice any symptoms from this deficiency, but I know that it is important for both my Crohn’s disease and health in general to maintain adequate vitamin D levels.

About 20 percent of people with Crohn’s disease have a vitamin B12 deficiency.

Vitamin B12 is a vitamin that’s essential for healthy red blood cell production, DNA synthesis, and for healthy functioning of the central nervous system.

This vitamin is found naturally in animal products, such as meat, fish, poultry, eggs, and dairy products. It’s also fortified into many breads and cereals.

People who follow vegan or vegetarian diets may not consume enough vitamin B12 through diet alone and may require supplementation.

Vitamin B12 is absorbed in the terminal ileum, which is the end of the small intestine right before it connects to the colon. This area is also the most common location for Crohn’s inflammation to exist.

With active inflammation in this area, it’s much more difficult to absorb vitamin B12 from food. If you’ve had surgery to this part of your intestines, you may also have difficulty absorbing vitamin B12.

Other causes of vitamin B12 deficiency in those with IBD include gastritis (inflammation of the stomach) and bacterial overgrowth in the small intestine.

A vitamin B12 deficiency can be quite serious and, over time, cause:

  • anemia
  • cognitive slowing
  • numbness
  • difficulty walking
  • peripheral neuropathy (more in the legs than the arms)

Treatment for vitamin B12 deficiency includes oral, sublingual, or intramuscular replacement. Intramuscular B12 shots may be required with active Crohn’s disease (terminal ileitis) or after surgery if the terminal ileum was removed.

My vitamin B12 levels run on the lower end, but I cannot say I have any symptoms from it. I do know my terminal ileum is affected by my Crohn’s disease, so I take oral vitamin B12 supplements to help maintain my levels, as I do not absorb enough from food alone.

Nutritional deficiencies are extremely common in those with Crohn’s disease and ulcerative colitis. These deficiencies can cause troublesome symptoms, affect quality of life, and even have potentially dangerous complications if left untreated.

I personally feel the best when my vitamin levels — especially iron — are in a healthy range.

Be sure to talk with a healthcare professional about your particular chances of developing nutritional deficiencies and make sure they’re appropriately treated.


Jamie Horrigan, MD, is a passionate Crohn’s disease advocate who truly believes in the power of nutrition and lifestyle. When she isn’t taking care of patients at the hospital, you can find her in the kitchen. For some awesome, gluten-free, paleo, AIP, and SCD recipes, lifestyle tips, and to keep up with her journey, be sure to follow along on her blog, Instagram, Pinterest, Facebook, and Twitter.