Crohn’s Disease and Ulcerative Colitis Nutrition Issues

Medically Reviewed by Minesh Khatri, MD on November 14, 2022
4 min read

If you have Crohn’s disease or ulcerative colitis (UC), getting enough nutrients from your diet often can be a challenge. That’s because these inflammatory conditions can affect everything from your appetite to bathroom habits to how well your body takes in vitamins and minerals.

The prefix “mal” means bad. Malnutrition happens when you lack, or are deficient, in essential nutrients. With Crohn’s or UC, that usually happens either because your body doesn’t absorb vitamins and minerals well or flushes them out (malabsorption).

People with Crohn’s disease often become malnourished over time. But ulcerative colitis tends to cause serious nutrition problems only during a severe flare-up or when you need to go to the hospital. That’s partly because UC affects only your colon (large intestine) and rectum. Absorption of most nutrients happens in the small intestine.

Crohn’s disease and UC are both types of inflammatory bowel disease (IBD). People with IBD often don’t get enough:

  • Calcium
  • Iron
  • Selenium
  • Zinc
  • Magnesium
  • Vitamins that dissolve in water, especially B12 and folate
  • Vitamins that dissolve in fat, like A, D, and K

The reasons that these two conditions can lead to malnutrition include:

Ulcers. These sores can make you bleed from your bottom. Your body may lose too much iron in the red blood cells. This may happen with both Crohn’s disease and UC.

Damaged small intestine. Inflammation makes it hard to break down food and to extract nutrients from what you eat and drink. So might surgery to remove a part of your small intestine. You especially might have trouble absorbing vitamins A, B12, D, E, or K well.

Diarrhea. This may leave you dehydrated and low on important electrolytes like sodium, potassium, magnesium, phosphorus, and zinc. Diarrhea can happen if your small intestine can’t hang on to bile acids or bile salts you need to digest fats. Or from inflammation in your colon. That can deplete your levels of vitamins K, A, and D.

Loss of appetite. Pain and nausea from your Crohn’s disease or UC may leave you in no mood to eat. Or you may avoid certain foods because they trigger your symptoms or eat a limited diet.

Medications. Drugs such as sulfasalazine and methotrexate can make it hard for your body to absorb folate, which your cells need to work right. This is more likely to happen with Crohn’s disease than with UC. Steroid medications can make it harder for your body to get phosphorus, zinc, and calcium.

Folate deficiency happens more often with Crohn’s disease, but can also develop if you have ulcerative colitis. You risk for colorectal cancer, anemia, and possibly cardiovascular disease is higher if this happens.

You can develop anemia because of this, which means you need more healthy red blood cells. Another reason for an iron deficiency is because your body isn’t absorbing nutrients like vitamin B12 and folate well. Medication can cause it too.

There are many clues when your body isn’t getting the right nutrients it needs to stay healthy.

Signs of malnutrition:

  • Losing weight unexpectedly
  • Feeling tired, weak, or lacking energy
  • Loss of muscle
  • Not eating a lot of food or eating only a few foods

Symptoms of malabsorption can include:


Weaker bones. Your bones need calcium and vitamin D to stay strong. Less physical activity, inflammation, and medicines like corticosteroids for a long time can weaken them and raise your chances for bone fractures. You also may get osteoporosis from pooping out a lot of fat and not getting enough fat-soluble vitamins.

Kidney stones. These mineral deposits can form if your body doesn’t absorb fat right.

Stricture. This is when your intestines get too narrow and block food from passing through. Repeated cycles of inflammation and scar tissue can lead to serious complications, including a blocked bowel.

Ask your doctor if vitamin and mineral supplements might help. Or your doctor could give you a special beverage to drink instead. These treatments are enteral nutrition. You can get all your nutrients from these liquids, or they can supplement what you eat.

If you can’t absorb any nutrients from food and liquids, you can get them through an IV. That is parenteral nutrition. You usually need this only for short periods. Most people do well with oral supplements.

For more serious cases, your doctor may recommend a feeding tube to replenish your nutrients. These types are common:

Nasogastric tube (NG tube). This goes through a nostril into your stomach.

Nasoduodenal tube (ND tube) or nasojejunal tube (NJ tube). It runs from a nostril to your small intestine.

Gastrostomy tube (G-tube) or jejunostomy tube (J-tube). It connects directly to your stomach or intestine through a hole in your skin.

These tips may help you avoid malnutrition:

  • Stay hydrated.
  • Avoid foods that make your symptoms worse. If you don’t know what those are, keep track of your diet in a journal and write down symptoms that come up.
  • Ask your doctor or nutritionist which foods are your best options for a balanced diet.
  • Get tested to check your vitamin and mineral levels and for any symptoms of malnutrition.