Dr. Berg’s Healthy Keto and Intermittent Fasting Podcast

The #1 Most Dangerous Fiber in the World

Apr 8, 2026
They explore how certain refined fibers can harm gut microbes and promote imbalance. The conversation highlights how processing removes polyphenols and turns fiber into ultra-processed microbial fuel. They cover links between refined fiber, rapid fermentation, SIBO risk, and animal findings suggesting serious harm. Practical advice centers on choosing whole-food fibers and fermented foods over isolated fiber additives.
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INSIGHT

Refined Fiber Lacks Polyphenol Guidance

  • Refined fiber is harmful because it's fiber without the plant's polyphenols which guide microbial growth.
  • Dr. Eric Berg explains polyphenols are tightly bonded to fiber in plants and act like an air-traffic controller for gut microbes.
INSIGHT

Polyphenols Direct Which Microbes Thrive

  • Polyphenols and fiber form a single unit in plants that microbiota evolved to process together.
  • The polyphenols selectively promote beneficial bacteria and suppress bad species when broken down by microbes.
INSIGHT

Whole Food Fiber Plus Polyphenols Amplifies Benefits

  • Eating foods that contain both fiber and polyphenols increases microbes that make short-chain fatty acids and reduces inflammation.
  • A 2025 review found whole-food combos (nuts, spices, whole grains) outperform fiber or polyphenols alone.
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