Fiber (Cellulose)

Summary

Fiber, derived from the Latin fibra meaning "fiber," primarily refers to cellulose, a complex carbohydrate and a key structural component of plant cell walls. Chemically, cellulose is a polysaccharide made up of long chains of glucose units linked by β-1,4-glycosidic bonds, rendering it indigestible to humans due to the absence of the enzymes required to break these bonds. Unlike other carbohydrates, cellulose passes largely unchanged through the small intestine and enters the colon.

Absorption & Damage within the intestines

Humans lack the enzymes necessary to break down cellulose, so it passes unchanged into the colon, where its abrasive, insoluble fibers physically damage the delicate mucous lining of the intestines. This constant mechanical irritation causes inflammation, thickening, and scarring of the gut wall, impairing nutrient absorption—a problem that worsens with age, leading to malnutrition and frailty.

Beyond the mechanical damage, bacterial fermentation of certain fibers produces acids—such as lactic and acetic acid—that lower the pH in the colon. While fermentation of soluble fibers is often portrayed as beneficial, excessive acidification actually harms our native beneficial gut flora, weakening this critical microbial ecosystem and allowing opportunistic pathogens to thrive. This imbalance further promotes inflammation and disrupts gut barrier function.

The bulk created by cellulose not only hardens stools but also increases strain during defecation, contributing to constipation and exacerbating conditions like irritable bowel syndrome (IBS). Chronic irritation and inflammation caused by fiber intake are implicated in a higher risk of colorectal cancer, undermining the widespread claim that all fiber supports colon health. The evidence clearly indicates that rather than being universally protective, insoluble fiber can be a source of gut distress and long-term health risks.

Negative effects

• Indigestible bulk: Passes unchanged through the gut, causing mechanical abrasion to the intestinal lining.

• Gut irritation: Chronic abrasion leads to inflammation, mucosal damage, and reduced nutrient absorption.

• Microbiota disruption: Fermentation acids lower colon pH, harming beneficial bacteria and promoting harmful microbes.

• Constipation and bowel strain: Increases stool hardness and size, worsening constipation and IBS symptoms.

• Colorectal cancer risk: Long-term inflammation from fiber abrasion linked to higher cancer risk.

• Malnutrition in elderly: Damage to gut lining impairs nutrient uptake, increasing frailty with age.

• Overhyped benefits: Fiber’s universal health claims overlook individual gut sensitivity and potential harm.