How does dietary fiber help regulate bowel movements?

From the Guidelines

Fiber helps bowel movements by adding bulk to stool and promoting regularity, with the most recent and highest quality study suggesting that adults should aim for 25-30 grams of fiber daily, particularly from soluble fiber sources like psyllium husk, to alleviate constipation symptoms. According to the 2022 study published in Gastroenterology 1, soluble fiber is efficacious in treating global symptoms of irritable bowel syndrome (IBS), while insoluble fiber may exacerbate bloating and abdominal pain. The study recommends selecting soluble fiber specifically among patients with constipation-predominant IBS (IBS-C).

Key Points to Consider

• Dietary fiber works by absorbing water in the intestines, making stools softer and easier to pass, with soluble fiber forming a gel-like substance that slows digestion, and insoluble fiber adding bulk to stool and helping it move more quickly through the digestive tract.
• Good sources of fiber include whole grains, fruits (especially those with edible skins), vegetables, legumes, nuts, and seeds, as well as fiber supplements like psyllium husk (Metamucil), methylcellulose (Citrucel), or wheat dextrin (Benefiber) 1.
• When increasing fiber intake, it's essential to drink more water (at least 8 glasses daily) to help the fiber work effectively, as recommended in the 2024 study published in Gastroenterology 1.
• The combination of fiber and fluid softens stool by drawing water into the intestines, increases stool bulk, stimulates intestinal muscles, and promotes the growth of beneficial gut bacteria that support digestive health.

Recommendations for Constipation Relief

• Adults should aim for 25-30 grams of fiber daily, gradually increasing intake to avoid gas and bloating.
• Select soluble fiber sources, such as psyllium husk, for constipation-predominant IBS (IBS-C).
• Drink at least 8 glasses of water daily to help the fiber work effectively.
• Consider fiber supplements like psyllium husk (Metamucil), methylcellulose (Citrucel), or wheat dextrin (Benefiber) if dietary changes are not sufficient.

From the FDA Drug Label

As your body adjusts to increased fiber intake, you may experience changes in bowel habits or minor bloating. Adults 12 yrs. & older 1 packet in 8 oz of liquid at the first sign of irregularity. The psyllium fiber supplement helps bowel movements by promoting regularity.

• It can be taken up to 3 times daily to help with irregularity.
• The product should be mixed with at least 8 ounces of water or other fluid to help with digestion. 2

From the Research

How Fiber Helps Bowel Movements

• Fiber plays a crucial role in maintaining healthy bowel movements by increasing stool bulk and softening stool, making it easier to pass 3.
• Insoluble fiber, such as cellulose, hemi-celluloses, and lignin, helps to add bulk to stool and promote regular bowel movements 4, 5.
• Soluble fiber, such as pectins, β-glucan, and hydro-colloids, is fermented by gut microbiota and can help to regulate bowel movements and prevent constipation 5, 3.
• A high-fiber diet can help to prevent constipation, diverticulitis, and other gastrointestinal disorders by promoting regular bowel movements and maintaining a healthy gut microbiome 6, 3.
• The physical and chemical properties of fiber, such as its water-holding capacity and susceptibility to bacterial fermentation, determine its physiological actions and benefits for bowel health 3.