In an all-too-common scenario, a patient goes to their doctor complaining about abdominal pain and a change in their bowel habits. The doctor offers a diagnosis of IBS and recommends that the person increase their intake of fiber. The patient then goes to the store and buys bran cereal. However, after a few days, they realize that their symptoms have worsened and they conclude "fiber is bad for IBS." Fiber is not necessarily bad for IBS, but bran might be! This overview of the relationship between bran and IBS will help you to be a better IBS food consumer.
What Is Bran?
Bran is the hard shell that comprises the outside layer of cereal grains, including barley, corn, millet, oats, rice and wheat. Bran provides a good dose of dietary fiber as well as being a good source of essential fatty acids, minerals, vitamins and other nutrients. A very 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.
Difference between Bran and Whole Wheat
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 wheat grain, namely the germ, endosperm and the bran. The large majority of whole wheat is made up of the endosperm, with the germ and bran comprising 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 therefore retains the fiber and other nutritional value offered by the bran.
IBS and Bran
In the not-so-distant 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 a whole array of IBS symptoms. A more recent study found a high dropout rate in study participants who were assigned to receive bran as the primary intervention. Other studies have shown that bran is no more effective than a placebo in alleviating IBS symptoms.
Why Bran Might Be Bad
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 carbohydrates identified within the FODMAPs group. Eating a diet high in FODMAPs has been associated with an increase in IBS symptoms.
So if bran is out, what is left? Luckily, there are other fiber alternatives. Fruits and vegetables are great sources of dietary fiber. There is also a whole host of other non-wheat bran, whole grain options.
In terms of fiber supplements, one of the most studied is psyllium, also known as 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. One small study found that flaxseed was superior to psyllium in easing symptoms of constipation, bloating and abdominal pain in constipation-predominant IBS (IBS-C) patients.
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 sub-types. Regardless of predominant symptom, 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.
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Ford, et.al. “Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis.” BMJ 2008 337:a2313.
Francis, C. & Whorwell, P. "Bran and irritable bowel syndrome: time for reappraisal." Lancet 1994 344:39-40.
Tarpila, S., et.al. "Efficacy of ground flaxseed on constipation in patients with irritable bowel syndrome" Current Topics in Nutraceutical Research 2004 2:119-125.