Does Oatmeal Irritate Your Stomach?

Oatmeal and upset stomach don't normally go together. Oatmeal is usually considered a healthy food, without many downsides. But some people are sensitive to oats, and there are a few reasons why.

Oatmeal is usually a healthy food. It's high in protein and soluble fiber, both dietary advantages, says the Harvard T.H. Chan School of Public Health. But oatmeal and upset stomach may occasionally be linked in people who are sensitive. This means that oatmeal, which provides many people with a good source of fiber, may need to be avoided if you are sensitive.

Oatmeal is made from oats, the edible seeds of oat grass, says the Harvard T.H. Chan School. The oats are usually cooked with added water or another liquid. When cooked, oats can be made into oatmeal, a slightly mushy food with a hearty texture. Oatmeal is a traditional breakfast food in parts of the world, including in the U.S.

The problem with oatmeal for sensitive people has a couple of likely origins. If you have celiac disease, you may be eating oats that have come into contact with wheat or wheat products, according to the National Celiac Association. If you have irritable bowel syndrome (IBS), you may be one of a few people who react to soluble fiber, according to the International Foundation for Gastrointestinal Disorders.

Celiac disease is a very serious intolerance to gluten. According to the Celiac Disease Foundation (CDF), if people with celiac disease eat gluten, the body's immune system attacks the small intestine. That can, in turn, mess with your body's ability to absorb nutrients.

Gluten is a protein found in wheat, rye and barley, CDF says. It helps foods maintain shape, and is often a hidden ingredient in processed foods. Oats, by their nature, don't contain gluten, CDF says, but oats are often grown near wheat, rye or barley, and cross-contamination may occur. CDF recommends that celiac patients eat only oats labeled as ‌gluten free‌.

If you experience stomach problems when eating gluten-free oats, it may be because you have an intolerance to the increase in fiber, CDF says. It could also be that you have developed a rare immune response to the oat protein ‌avenin‌, similar to what happens with gluten. If you have celiac disease and want to eat oatmeal or any other oat product, you should talk with your doctor first.

Oats contain the protein called avenin. It's rare that people with celiac disease also develop an immune response to avenin, but it can happen, the CDF says. A study reported in the December 2016 issue of the journal ‌Medical Sciences‌ found that a very few celiac patients reacted to avenin.

A minority of people with IBS react to soluble fiber, which is found in vegetables, fruits and oat cereals, says the International Foundation for Gastrointestinal Disorders (IFGD). Soluble fiber dissolves in water, unlike insoluble fiber.

Oat bran contains both types of fiber. The IFGD suggests that if you have IBS, you should try different types of fiber to see if you get diarrhea after eating oatmeal or get what you think is an oatmeal-based sore stomach. As always, check with your doctor if you think oatmeal is the cause of your upset stomach to rule out any serious health problems.