How to identify the health benefits and risks of bran

Bran is the indigestible outer husk of cereal grains. A number of best-selling books turned bran into the fad food of the 1970s, and raw miller's bran was added to everything from bread to meat loaf. We now know that various types of bran have different properties. Wheat bran, for example, is mostly insoluble fibre, which makes its way through the intestinal tract intact. When used in moderation, insoluble fibre helps prevent constipation by producing a soft, bulky stool that moves quickly and easily through the colon. Here are some tips on getting the most from adding bran to your diet.

Bran was once thought to prevent colon cancer, but studies have produced mixed results.

• An Australian study found that women taking large amounts of wheat bran actually had a slightly increased incidence of colon cancer.
• In contrast, a four-year study involving 58 high-risk adults with precancerous colon polyps found that those taking wheat bran achieved a reduction in the size and number of these growths.
• Two 2003 medical studies showed that dietary fibre is associated with a lower risk of colorectal cancer.
• In one study, investigators compared the daily fibre intake of more than 3,500 people who had precancerous colon polyps to the fibre intake of about 34,000 people who did not have these growths. They found that the people who ate the most fibre, about 35 grams (1 1/4 ounces) daily, had a 27 percent lower risk of precancerous growths than those who ate the least.
• Including wheat bran in a high-fibre diet may also help prevent diverticulitis, an intestinal disorder in which small pockets bulging from the colon wall become impacted and inflamed. And because it helps prevent constipation, bran may also be beneficial for hemorrhoid sufferers.

Oat bran is high in soluble fibre, which is sticky and combines with water to form a thick gel.

• Some researchers have reported that this type of fibre reduces blood cholesterol levels.
• Oar bran also appears to improve glucose metabolism in diabetics, which in turn reduces their need for insulin and other diabetes medications.
• All types of bran and high-fibre foods help control weight by promoting a feeling of fullness without overeating.
• There is a lowered incidence of some obesity-related cancers and heart attacks among populations with high-fibre diets.

When bran's benefits were first announced, many people started adding huge amounts of raw miller's bran to their daily diet, which could cause bloating and discomfort and also aggravate irritable bowel syndrome.

• The phytic acid in raw bran inhibits the body's absorption of important minerals — but during bread baking, yeast enzymes destroy much of the phytic acid.
• Processing also destroys most phytic acid in high-bran cereals.
• There have been reports of severe bowel obstruction in people who consumed large amounts of bran, especially if they don't drink enough water.

Many nutritionists now advise people to eat whole-grain wheat bread or cereals, so eat oatmeal and cereals made with whole oats; substitute brown rice for white. These foods are also more palatable than raw bran, which tastes like sawdust.

Benefits

• Helps prevent constipation.
• Oat and rice brans help lower blood cholesterol levels.
• Promotes a feeling of fullness, which can lead to weight loss.
• May reduce the risk of some cancers.

Drawbacks

• Excessive bran consumption reduces the absorption of calcium, iron and zinc.
• Can cause intestinal irritation, bloating and gas.