Constipated? Why More Fiber Might Not Be the Answer

About 20 percent of adults have chronic constipation. The standard remedy? Increase your fiber intake. But it’s important to realize that might not always be the solution.

“Eating more fiber has been shown to soften stool and improve stool frequency in patients with constipation. It’s the first-line treatment due to its potential benefits, low cost and minimal side effects,” says University Hospitals gastroenterologist Vu Nguyen, MD. “But increased fiber intake may sometimes worsen constipation. And the role of fiber supplement in IBS or IBD patients is more complex.”

Dietary Fiber: Soluble and Insoluble

Dietary fiber is the non-digestible carbohydrate content in all plant foods, including whole grains, nuts, seeds, fruits and vegetables. Both types of dietary fiber – soluble and insoluble – can be found in many high fiber foods and both help with proper bowel function.

Soluble fiber dissolves in water and forms a gel that helps soften stool and increase stool frequency. Good sources of soluble fiber include oats, beans, citrus fruits and avocado, and psyllium fiber supplements such as Metamucil.

Insoluble fiber doesn’t break down in gastrointestinal fluids and passes straight through the gut undigested. This adds to the stool bulk and stimulates movement through the gut. Good sources of insoluble fiber include wheat bran, nuts, vegetables and dried fruits.

How Much Dietary Fiber Do You Need?

The Academy of Nutrition and Dietetics recommends 14 grams of fiber for every 1,000 calories you consume. If you’re constipated and aren’t getting the recommended amount of fiber, increasing your fiber intake with foods or supplements may bring relief. If you increase your fiber intake, be sure to increase your fluid intake as well.

When More Fiber Might Not Be the Answer

Inadequate fiber intake can cause constipation. But it’s not the only cause. There are times when adding fiber can be ineffective or even cause a problem. Dr. Nguyen explains more.

When there’s no improvement or other symptoms appear: Patients with constipation who don’t improve after a trial of fiber supplement and laxatives or have new symptoms, should see a gastroenterologist. Symptoms such as rectal bleeding, abdominal pain or weight loss indicate more complex problems that require evaluation and proper treatment.

When there’s excessive bloating, gas and cramps: Some patients with constipation have excessive abdominal cramps, bloating and gas. The highly fermentable fiber in some cereals (rye, wheat), legumes (bean, lentil), vegetables (broccoli, cabbage, Brussels sprouts), and fruits (apple, peach) may worsen these symptoms. If you have these symptoms, avoid these foods.

In patients with IBS or IBD: “Patients with IBS or IBD should see a gastroenterologist and dietitian to discuss diet and therapy,” says Dr. Nguyen.

Irritable bowel syndrome (IBS) symptoms include recurrent abdominal pain related to bowel movements, a change in stool frequency and/or a change in stool consistency (appearance). IBS is divided into subtypes:

• IBS-C (constipation) has predominantly hard stools. For patients with IBS-C, soluble fiber from sources such as psyllium and oat bran are recommended to help relieve symptoms. However, insoluble fiber such as wheat bran, whole grain and some vegetables don’t provide significant benefits.
• IBS-D (diarrhea) has predominantly liquid stools. For patients with IBS-D, soluble fiber is recommended.
• IBS-U (unclassified) meets the criteria for IBS but can’t be reliably characterized into other IBS subtypes. For patients with IBS-U, soluble fiber is recommended.

Inflammatory bowel disease (IBD) includes the autoimmune conditions of ulcerative colitis and Crohn’s disease. “There is little evidence to support a high fiber diet in ulcerative colitis,” Dr. Nguyen says. “And in Crohn’s disease, insoluble fiber is not recommended in patients with active symptoms, particularly if a bowel blockage or stricture is suspected.”

“If you have occasional constipation or have chronic constipation but don’t get enough fiber, adding fiber can often help. But if increasing fiber doesn’t work or your constipation is accompanied by other symptoms, it’s important to see a gastroenterologist to diagnose the problem and get the right care.”

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The digestive health experts at University Hospitals have the expertise to diagnose and manage the full spectrum of gastrointestinal disorders. Nutritional counseling is also available when dietary modifications are recommended as part of your total treatment plan.