Which statement best describes insoluble fiber and its health effect?

• A. Insoluble fiber adds bulk and supports bowel regularity.
• B. Insoluble fiber dissolves in water and can reduce cholesterol.
• C. Insoluble fiber is primarily used to provide energy.
• D. Insoluble fiber is not fermentable by gut bacteria.

Answer: (A)

Insoluble fiber adds bulk to stool, which helps move waste through the digestive tract and promote regular bowel movements. Because it doesn’t dissolve in water, it remains as larger particles that increase stool mass and speed up transit, reducing constipation and supporting gut health. This bulk-forming effect is the main health benefit you get from insoluble fiber, and it helps maintain regularity and lower the risk of issues like hemorrhoids and diverticular disease.

By contrast, soluble fiber dissolves in water and can form gels that help lower cholesterol by binding bile acids, which is why soluble fiber is often linked to cholesterol reduction. Insoluble fiber isn’t focused on that cholesterol-lowering action. It’s also true that insoluble fiber is less fermentable by gut bacteria than soluble fiber, though some fermentation can occur; its standout role remains adding bulk and supporting regularity.