Avoid These 9 Supplements if You Have Ulcerative Colitis
Digestive HealthUlcerative Colitis

9 Supplements to Be Careful With if You Have Ulcerative Colitis

9 Supplements to Be Careful With if You Have Ulcerative Colitis
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Published on August 31, 2026
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It’s wise to be choosy when it comes to supplements. That’s especially true when you have ulcerative colitis (UC), because some can negatively impact your condition.

“I hear the ‘It’s natural, so what’s the harm?’ argument quite a bit,” says Andrew Dam, DO, a gastroenterologist with Pomona Valley Hospital Medical Center in Pomona, California. But certain supplements "can cause [gastrointestinal] symptoms and interact with medications, and many haven’t been studied very well in UC,” Dr. Dam says.

That’s especially true for the following herbs, vitamins, minerals, and other supplements. While not everyone with UC may need to steer clear, you should check with your gastroenterologist before taking them to decide if they’re right for you.

1. Laxative Herbs

Up to half of people with UC experience constipation symptoms.

 Laxative herbs like senna, cascara sagrada, and aloe latex can help you have a bowel movement — but they can also potentially cause forceful diarrhea, urgency, bloody stools, and abdominal pain and cramping.

“They can make an already irritated colon feel worse,” Dr. Dam says. Aloe latex is particularly risky because use of it is linked to liver problems.

Oral laxatives might also impact how your body absorbs medications, potentially making your UC meds less effective. They can also reduce absorption of nutrients from food, making it even harder to stay nourished when you have UC.

If you’re struggling to have regular bowel movements, let your gastroenterologist know before taking an herbal laxative. “If someone with UC is constipated regularly, I’d rather figure out why and then choose [a treatment that’s] more predictable,” Dam says.

2. Magnesium

Magnesium is another dietary supplement that can irritate your GI tract and potentially worsen symptoms that you might already be dealing with, like loose stools or diarrhea.

 Forms like magnesium carbonate, chloride, glyconate, and oxide tend to be more irritating, while magnesium glycinate is often gentler.

Aside from making you uncomfortable, supplements like magnesium that exacerbate your symptoms can make it harder for you and your doctor to have a clear sense of what’s happening with your UC. “It’s going to obscure the whole picture. Is your diarrhea from your UC or from a supplement?” says Supriya Rao, MD, a gastroenterologist with Tufts Medicine in Lowell, Massachusetts.

Keep in mind that the mineral can show up in many different supplement products where magnesium isn’t the main selling point, such as electrolyte powders, sleep aids, and antacids. Check labels to make sure you’re not getting an unexpected dose of magnesium from a product.

3. High-Dose Vitamin C

Some people turn to vitamin C during the winter months to give their immune system a boost. While research hasn’t shown that supplementing with vitamin C can actually help ward off a cold, the data is clear on one thing: Taking megadoses of vitamin C (more than 2,000 milligrams [mg] daily) can make UC symptoms like loose stools or cramping worse.

Neither vitamin C or magnesium have to be totally off-limits when you have UC. But you should talk with your gastroenterologist before taking them to come up with a plan. “If there’s a reason to take magnesium or vitamin C, I’d stick with a reasonable dose and back off if it starts causing [gastrointestinal] symptoms,” Dam says.

4. Oral Iron Supplements

It’s not uncommon for people with UC to be iron deficient (anemia), which can be caused by inflammation, rectal bleeding, or dietary restrictions.

 But if you suspect that you’re low, you should have your levels confirmed with a blood test and talk with your doctor about the best way to bring your iron back up, says Dr. Rao.
Your provider may recommend IV iron infusions over pills taken by mouth. Infusions can raise iron faster, and they’re less likely to cause side effects like nausea, diarrhea, constipation, or abdominal pain, which can be common with oral iron.

5. Fiber Supplements

Fiber-rich diets can be helpful for UC when you’re in remission, because they can support better gut health.

 But experts generally agree that it’s better to try to meet your fiber needs through foods like fruits and vegetables, whole grains, and beans or other legumes.

“[Fiber supplements] can cause bloating, gas, and cramping, especially if you add too much too quickly,” Dam says.

If you need an extra boost to get the recommended 25 to 34 grams (g) of fiber per day, it may make sense to ask your gastroenterologist about supplementing. “Psyllium is the best-studied option and it tends to be the best tolerated,” Rao says.

6. Probiotics

Foods that are naturally rich in probiotics (like yogurt and sauerkraut) can be part of a healthy diet for people with UC. But experts don’t recommend using probiotic supplements as part of your UC management plan, except for certain complications like pouchitis.

“The problem is that probiotics aren’t all the same, and we don’t have strong evidence to routinely recommend them for UC,” says Dam.

And though there’s limited evidence on the efficacy of probiotics, some studies suggest that people with inflammatory bowel diseases (IBDs) like UC may be more prone to probiotic side effects.

7. Immune-Boosting Herbs

Products containing echinacea, astragalus, Asian ginseng, ashwagandha, mushroom blends, or others that claim to bolster your immune system deserve extra scrutiny when you have UC.

There’s limited evidence showing how immune-boosting herbs impact people with inflammatory gastrointestinal conditions, and it’s possible that they could interact with your UC medications, Dam says. “If there isn’t a clear benefit, I don’t see much reason to take that chance,” he adds.

8. Supplements That May Increase Bleeding

Garlic, ginkgo biloba, ginseng, and high-dose omega-3s are just a few of the products that may affect blood clotting.

 That doesn’t mean that everyone with UC needs to avoid them, but if you’re experiencing rectal bleeding from a flare, they might make the problem even worse.

In that case, “I’d want to review everything they’re taking and probably avoid nonessential supplements that could add to the bleeding risk,” Dam says.

9. Supplements With Sugar Alcohols

Always check the label for pills, powders, shakes, or gummies that bill themselves as low-sugar or sugar-free. They may be sweetened with sugar alcohols like xylitol, erythritol, sorbitol, or mannitol, among others. While not unsafe in small amounts, they’re notorious for causing gas, bloating, and diarrhea — and the effects tend to be worse in people with GI issues like irritable bowel syndrome, which research has estimated occurs alongside IBDs like UC anywhere from 11 to 64 percent of the time.

EDITORIAL SOURCES
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