Crohn’s disease may cause a deficiency of essential nutrients due to malabsorption, limited diet, and symptoms such as diarrhea. A person with Crohn’s disease may lack essential nutrients, including iron, calcium, and vitamin D.

According to the Crohn’s & Colitis Foundation (CCF), malnutrition is common in inflammatory bowel disease (IBD), especially in Crohn’s disease, with studies indicating that it affects 20–85% of people with IBD.

The CCF also notes that approximately 60% of people with IBD feel that nutrition plays an important role in managing their condition. However, few discuss diet with a doctor.

This article explains which vitamins, minerals, and other nutrients a person with Crohn’s disease may lack. It also outlines the signs and symptoms related to deficiencies in these nutrients.

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Crohn’s disease causes inflammation in the gastrointestinal (GI) tract, commonly affecting the small intestine and the beginning of the large intestine.

However, inflammation can be present in any part of the GI tract and through the entire thickness of the intestinal wall.

Inflammation can cause difficulty digesting and absorbing nutrients. Doctors refer to this as malabsorption.

Malabsorption can lead to deficiencies in essential vitamins, minerals, and other nutrients, resulting in further health complications.

Additionally, some symptoms of Crohn’s disease can lead to malnutrition:

Can a person’s diet lead to Crohn’s disease?

The CCF notes that although a person’s diet can aggravate Crohn’s disease, it does not cause the condition.

Crohn’s disease can occur due to genetic and environmental factors.

General signs of malnutrition include:

People with Crohn’s disease can experience weight loss. A 2014 study reports that 57% of people may lose a significant amount of weight before a doctor diagnoses the condition.

Weight loss can also continue throughout the disease. Another study indicates that this affects 65–75% of people with the condition.

People with Crohn’s disease may have difficulty consuming enough calories or macronutrients from food. Macronutrients include protein, fats, and carbohydrates.

This can be the result of diarrhea and eating less food in an effort to avoid aggravating symptoms.

When a person does not consume enough calories, protein, and other essential nutrients, protein-energy malnutrition can occur.

Protein-energy malnutrition causes changes in body composition. For example, people with Crohn’s disease may develop malnutrition over a long period, resulting in sarcopenia, which is a loss of muscle mass and strength.

A person with Crohn’s disease may develop a deficiency in the following vitamins and minerals:


Rectal bleeding that results from stomach ulcers and insufficient iron consumption can lead to iron deficiency.

Signs that a person may have iron deficiency include:

Doctors can diagnose iron deficiency with a simple blood test.


According to a 2017 article, calcium deficiency in people with Crohn’s disease can result from insufficient consumption of dietary calcium or decreased intestinal or renal absorption.

People with Crohn’s disease may also have low levels of vitamin D, which may render the body unable to absorb calcium.

Calcium deficiency can lead to osteoporosis, or decreased bone density.

The National Institutes of Health state that the signs of calcium deficiency are not obvious. However, severe calcium deficiency can manifest with tingling and numbness in the fingers.

Vitamin D

People with Crohn’s disease may have vitamin D deficiency due to malabsorption and inadequate intake.

Vitamin D is essential for normal bone metabolism and the functioning of the immune system. Without enough vitamin D, a person can develop osteomalacia, which is when existing bones become weak.

Signs of severe vitamin D deficiency include bone pain and muscle weakness.


A person with Crohn’s disease can develop a zinc deficiency due to a limited diet, diarrhea, or malabsorption.

Symptoms of zinc deficiency include:


Malabsorption and chronic diarrhea can result in a magnesium deficiency in those with Crohn’s disease. Magnesium helps regulate nerve and muscle function, blood pressure, and blood sugar levels.

Signs of magnesium deficiency are not immediately obvious. However, symptoms can include:

  • loss of appetite
  • nausea
  • vomiting
  • weakness
  • fatigue

A severe deficiency can cause:

  • numbness
  • muscle cramps
  • tingling
  • seizures
  • changes in personality
  • abnormal heart rhythm

B vitamins

There are eight B vitamins that help the body make energy from the food a person eats and form red blood cells.

A deficiency in B vitamins can develop in people with Crohn’s disease due to malabsorption and reduced intake. Vitamin B12 deficiency can also occur in those who have undergone an ileal resection.

Signs of vitamin B deficiency vary depending on which vitamin B is insufficient in a person’s body.

Learn more about the symptoms of vitamin B deficiency here.

Vitamin A

A person may experience vitamin A deficiency due to malabsorption and low intake.

Vitamin A is an important antioxidant nutrient for the immune system and supports the cells in the gut lining.

Poor wound healing and night blindness can be symptoms of vitamin A deficiency.

Vitamin K

A deficiency in vitamin K may arise due to malabsorption, a limited diet, or the use of antibiotics.

Vitamin K is a nutrient that is important for bone health, blood clotting, and other bodily functions.

If a person develops severe vitamin K deficiency, they can experience problems with bleeding and bruising. It can also reduce bone strength.

Severe diarrhea can cause dehydration and depletion of electrolytes, such as sodium and potassium.

Sodium plays a role in the functioning of muscles and nerves. It also helps maintain the balance of fluids in the body.

Potassium helps nerve and muscle function as well. It also supports regular heartbeat.

If a person’s potassium level is too low, they may experience:

Therefore, if a person has chronic or severe diarrhea, they should consult a doctor, who may prescribe medications or supplements to address electrolyte imbalances.

The CCF recommends people ask a doctor for tests for nutrient deficiencies even if they are not showing any symptoms of malnutrition.

Furthermore, people should avoid foods that worsen their symptoms, and work with a doctor to identify a list of nutritious foods they can eat.

Certain foods may be easier for people with Crohn’s disease to digest. These include:

A doctor may advise a person to avoid certain foods when they are experiencing a flare or if they have a stricture, which is a narrowing of the intestine due to inflammation or surgery.

People should work with a doctor to clarify what foods are right for them according to their symptoms and whether they are experiencing a flare.

Learn more:

Vitamin and mineral supplements can help prevent a deficiency and avoid further health issues.

A doctor or dietitian can advise a person with Crohn’s disease about what supplements to take.

Some supplements can cause GI symptoms, and people should check the ingredients for sugar alcohols, lactose, and artificial coloring. Furthermore, it may be best to avoid taking supplements on an empty stomach.

Supplements are available as tablets, liquid supplements, and oral nutrition products. A healthcare professional can advise a person which one is most suitable for them.

Further resources

For more in-depth resources about vitamins, minerals, and supplements, visit our dedicated hub.

Was this helpful?

People with Crohn’s disease are likely to experience malnutrition and weight loss. They can also develop deficiencies in essential vitamins, minerals, and macronutrients, leading to further health issues.

It is advisable for people with Crohn’s disease to work with a healthcare professional to identify which foods they can eat for adequate nutrition.

Doctors or dietitians can also help determine whether a person with the condition needs supplements and which are best for the person’s needs.

People with Crohn’s disease should get tests for nutritional deficiencies regularly, even if they are not presenting with any symptoms.