Is Fish Oil Good for Ulcerative Colitis?

Medically Reviewed by Sabrina Felson, MD on June 06, 2024
4 min read

Ulcerative colitis (UC) causes inflammation and sores (called ulcers) in the innermost lining of your colon. This can cause symptoms like diarrhea or belly cramps. Inflammation and ulceration of the absorptive cells lining the colon can affect your body’s ability to absorb important vitamins and minerals. Some medications and surgery can cause this, too.

Some studies have found that fish oil, which contains a type of fat called omega-3 fatty acids, has anti-inflammatory properties that may reduce or prevent inflammation in the colon. But can it really help? Here’s a look at what research has to say about the benefits of fish oil for ulcerative colitis.

Fish oil is a type of food that often contains omega-3 fatty acids. Your body needs omega-3s for a lot of functions like cell growth, fighting diseases, energy production, and muscle activity. But your body can’t make them naturally, so you have to get them through foods or supplements.

There are three types of omega-3s:

  • ALA (alpha-linolenic acid)
  • DHA (docosahexaenoic acid)
  • EPA (eicosapentaenoic acid)

Fish oil can be a good source of omega-3s and contains DHA and EPA. The fatty acid is known for its anti-inflammatory effects on your body, especially against specific conditions like heart disease, high blood pressure, cholesterol, and rheumatoid arthritis.

While there’s no cure for UC, growing research suggests that fish oil may help reduce or prevent inflammation in your colon. Not only this, but some studies claim omega-3s can also reduce the need to take anti-inflammatory drugs and promote healthy weight gain in people with UC.

How does it work? UC leads to an increase in leukotriene B4 levels in the innermost layers of the colon. It’s a type of chemical agent that triggers inflammation. High levels of it are associated with a more serious case of UC. Studies claim omega-3 fatty acids found in fish oil can reduce or prevent the rise in leukotriene B4, which lowers the inflammation in your gut.

A small study with 11 men with mild to moderate UC tested this. They were split into two groups. One group got fish oil for 3 months while the other got olive oil for 3 months. Then the groups switched treatments. The study found that those who got fish oil saw their UC symptoms improve by 56%. Moreover, eight men who were taking fish oil could reduce or stop taking anti-inflammatory drugs. However, the fish oil didn’t reduce leukotriene B4 levels in the colon.

Another small study saw similar results. In this study, several participants were able to cut down on their daily dose of prednisone, a steroid anti-inflammatory drug that can cause side effects, by up to 66%. Some experts believe that the EPA found in omega-3 fatty acids stops leukotriene B4 from causing a spike in inflammation levels, which then causes UC symptoms to improve.

But more research needs to be done to better understand if omega-3 fatty acids benefit UC and how much you might need to take for it to work.

Omega-3 fatty acids are naturally found in high levels in fatty fish. This includes:

  • Herring
  • Wild salmon
  • Bluefin tuna
  • Mackerel
  • Sardines
  • Anchovies
  • Lake trout
  • Striped bass

Fatty fish mostly contain DHA and EPA, and it’s the best way to get omega-3s into your body. To get the most out of your fish, you can either bake or broil it. But don’t fry it. You can also eat canned tuna, but watch out for high levels of mercury. Canned light tuna has less mercury than albacore, white, or yellowfin tuna. If you’re pregnant or nursing, avoid high-mercury fish such as swordfish, tilefish, and sharks.

Besides fish, there are other foods that contain omega-3s. If you’re vegan, vegetarian, or allergic to seafood, you can opt for plant-based sources, such as:

  • Flaxseed oil
  • Canola oil
  • Chia seeds
  • Walnuts
  • Soy foods
  • Pumpkin seeds

Plant-based omega-3s contain ALA. Your body has to convert this into DHA and EPA. Since this process isn’t the best way to get omega-3 fatty acids, you might have to eat more of it or supplement your diet with fish oil to meet the daily recommended amount.

It’s best to get your omega-3s directly from food for UC. If you’re unable to, taking fish oil supplements can boost your overall intake. But dosages can vary, and it does cause a few side effects. Before you start taking it, ask your doctor if fish oil supplements are right for you.

The U.S. Department of Agriculture recommends at least 8 or more ounces of oily fish per week, which is about 250 milligrams of omega-3 fatty acids. This looks like two servings of fish per week to meet the minimum requirement.

If you take the recommended amount of omega-3 fatty acids, it’s generally considered safe and beneficial for your overall health. But supplements may cause mild side effects, such as:

  • A fishy aftertaste
  • Bad breath
  • Heartburn
  • Nausea
  • Diarrhea
  • Rash

Taking very high doses of omega-3s can increase the risk of bleeding and stroke. Omega-3s can also interact with some medications and foods, changing their overall effect.

These include:

  • Anticoagulant (blood clotting) drugs or supplements
  • Blood pressure medicine, herbs, or supplements
  • Birth control drugs, which can interfere with fish oil effects
  • Orlistat (Xenical, Alli), a type of weight loss drug, which can lower fish oil absorption
  • Vitamin E levels, which may dip when you take fish oil

If you have UC and you’re planning to include fish oil in your diet, check with your doctor if it’s right for you. If you’re allergic to seafood, experts aren’t sure if fish oil is safe for you. If you do take it, monitor for side effects and if you have an allergic reaction, get immediate medical help.

Note that the FDA regulates supplements under a different set of regulations than it does drugs or food.