Why Bran Is Bad for IBS

In an all-too-common scenario, you go to your doctor complaining of abdominal pain and a change in your bowel habits. Your doctor offers a diagnosis of irritable bowel syndrome (IBS) and recommends that you increase your intake of fiber. You then go to the store and buy bran cereal. However, after a few days, you realize that your symptoms have worsened and you conclude "fiber is bad for IBS." Fiber is not necessarily bad for IBS, but bran might be. Learn about the relationship between bran and IBS to help you to be a better IBS food consumer.

Bran is the hard shell that comprises the outside layer of cereal grains, including barley, corn, millet, oats, rice, and wheat. Bran provides a large dose of dietary fiber as well as being a good source of essential fatty acids, minerals, vitamins, and other nutrients. A visible example of the difference between a grain with bran versus one in which the bran has been removed is rice. Brown rice has the bran layer intact, while white rice has had the outer layer removed.

Although bran is a part of a variety of cereal grains, products such as bran cereal or muffins are typically prepared with wheat bran.

Products that are labeled as "bran" or "all-bran" are made of just that, the outer bran coating of wheat grains. Whole wheat products are those that are made with a flour that consists of all three parts of the wheat grain, namely the germ, endosperm, and the bran. A large part of whole wheat is made up of the endosperm, with the germ and bran contributing smaller percentages.

White flour is considered to be refined in that the germ and bran are removed. This is done primarily to add to the shelf life of the product, as the bran and germ contain fats that can go rancid. The unfortunate result of this refinement is that by taking out the bran, the fiber content of the flour is reduced. Since whole wheat flour contains the bran portion of the grain, it retains the fiber and other nutritional value offered by the bran.

In decades past, doctors recommended bran to their IBS patients with the rationale that the increase in dietary fiber should help to improve bowel regularity. However, a landmark study published in the early 1990s was the first to identify that bran tended to make IBS patients feel worse, exacerbating an array of IBS symptoms. In its 2014 research review, the American College of Gastroenterology concluded that insoluble fiber sources, like wheat bran, are not recommended for IBS due to the risk of increased gas and bloating.

There is no specific research or definitive answer as to why bran might be a problem for IBS patients. One theory is that the hard bran shell is somehow irritating to the nerves in the lining of the intestines. Another possibility may have to do with the fact that wheat contains fructans, one of the types of fermentable carbohydrates identified within the FODMAPs group. Eating a diet high in FODMAPs has been associated with an increase in IBS symptoms.

Luckily, there are other fiber alternatives to bran. Fruits and vegetables are great sources of dietary fiber. There are many other non-wheat bran, whole-grain options.

In terms of fiber supplements, one of the most studied is psyllium, also known as an isphagula husk. Although studies vary in quality and in results, there is a trend toward IBS symptom improvement with the use of psyllium. Another option, particularly if your primary symptom is constipation, is ground flaxseed.

Although a diet high in dietary fiber is optimal for digestive health, in terms of IBS symptoms, an increase in fiber is typically seen as more helpful for IBS-C than the other IBS subtypes. Regardless of the predominant symptoms, there is some evidence that soluble fiber is better tolerated than insoluble fiber. In order to avoid an exacerbation of symptoms, it is best to use a slow approach when increasing your fiber intake to allow your body to adjust to the change.