Why Bran Is Bad for IBS

Bran fiber can make irritable bowel syndrome (IBS) symptoms worse. Many experts in gut health do not recommend wheat bran for people with IBS, but some people with the condition might be able to tolerate it.

If you have IBS, it's important to include fiber in your diet because not getting enough fiber can also make your IBS symptoms worse. However, not all sources of fiber are the same. You may find that some types of fiber work better for you than others.

This article will explain why bran fiber is different from other kinds of fiber and why it can make symptoms of IBS worse. You will also learn about types of fiber that are IBS-friendly.

Bowls of oat bran and oat bran flakes
Westend61 / Getty Images

What Is Bran?

Bran is a fiber that gets taken out of the hard outer layer of cereal grains like barley, corn, oats, rice, and wheat.

Cereals, muffins, and other products made with whole wheat flour usually have bran in them. Whole wheat flour is made of the inner part of the grain kernel (wheat germ), the bulk of the grain kernel (endosperm), and bran. In the flour, these are all milled together.

Bran helps with digestion and provides more nutrition than white (refined) flour. Wheat bran is an excellent source of potassium, iron, magnesium, and vitamin B6. A one-cup serving of wheat bran also provides 100% of your daily recommended intake of fiber.

Is Bran Bad for IBS?

It’s not clear why bran seems to make symptoms worse for some people with IBS, but researchers have some theories:

  • One theory is that the hard bran shell is irritating to nerves in the lining of the intestines. These nerves are part of the enteric nervous system (ENT) in the gut that helps regulate the digestive process. ENT dysfunction is thought to be a major factor in IBS, and irritation from bran may make it even harder for the ENT to work properly.
  • Another possibility is that wheat bran contains fructan, one of several substances classified as a FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols). These are short-chain carbohydrates that are found in many foods. FODMAPs can ferment and increase the amount of liquid and gas in the intestines. A diet that’s high in FODMAPs is believed to be linked to an increase in IBS symptoms.
  • A simple explanation is that a standard serving of wheat bran is just too much for some people with IBS to handle. Wheat bran attracts water into the intestines, making stools softer and helping ease digestion (insoluble fiber). However, if you eat too much, it can increase gas production, leading to bloating and flatulence.

Cutting back on your bran intake might be all that is needed to help with your IBS symptoms. Over time, you can try slowly increasing the amount of bran that you eat as your body gets more used to it. If it’s still bothering you, consider switching to a different kind of fiber. 

IBS-Friendly Bran Fiber Alternatives

Fiber is not digested by the body but it still plays an important role in digestion. Ideally, you want to get a mix of two kinds of fiber: soluble fiber and insoluble fiber. Bran is an insoluble fiber.

Soluble fiber absorbs water and helps keep stool soft. Insoluble fibers are “rough,” and their role is to encourage your intestines to move and push stool through your GI tract so you can have regular bowel movements.

While insoluble fiber like bran can make IBS worse, soluble fiber can be beneficial for some people with IBS.

If wheat bran is making your IBS worse, here are some sources of soluble fiber that might be less irritating:

  • Beans
  • Blackberries
  • Blueberries
  • Banana
  • Kiwi
  • Pineapple
  • Eggplant
  • Carrots
  • Collard greens
  • Green beans
  • Green peas
  • Kale
  • Zucchini
  • Nuts
  • Chia seeds
  • Potatoes
  • Spinach

You might be able to better tolerate non-wheat sources of bran (such as corn, oats, and rice).

Fiber supplements such as psyllium may help with IBS symptoms. Another natural option that can be helpful for constipation is ground flaxseed.

How Much Bran Fiber Can I Have With IBS?

A diet high in fiber helps most people with their digestive health, but the general recommendations may not work as well for people with IBS.

Some studies have shown that fiber might be more beneficial for people with constipation-predominant IBS (IBS-C) than the other IBS subtypes.

Not getting enough fiber in your diet can also make your IBS worse. Try to get 20-35 grams of fiber a day. That said, you don’t have to eat that much at once. You can slowly work your way up to that goal and adjust as needed to control your symptoms. 

Ultimately, you’ll need to do some experimenting with your diet to figure out which kinds of fiber (and how much) you are able to tolerate. What works for one person with IBS may not work for someone else.

Some people with IBS notice that foods that didn’t bother them before start to over time, or that foods they used to have to avoid have become more tolerable.

Paying attention to your symptoms and trying to tie them back to what you eat and drink can help you manage your IBS more effectively

If you’re having a hard time figuring out what’s making your IBS worse, talk to your provider. They can problem-solve with you and identify factors that could be contributing to your symptoms, then find ways to fix them.


If you have IBS, you may find that bran is not something you tolerate well. Bran has a lot of insoluble fiber, which can make IBS symptoms worse. You should still try to get fiber in your diet, but you may find that focusing on sources of soluble fiber or using fiber supplements is a better option for you.

A Word From Verywell

If you're unsure of which sources of fiber are best for you, consider meeting with a dietitian experienced with IBS to work out a dietary plan. Often, finding the best fit takes trial and error.

It's always best to use a gradual approach when increasing your fiber intake, or when trying new foods, to allow your body time to adjust to the change.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.