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Providing perspectives on recent research into vitamins and nutritionals


Eat Fiber for the Health of Your Gut, Liver and Kidneys

By Michael McBurney

People don’t eat enough dietary fiber. We just don’t and we aren’t changing our habits. The average intake of US adults still hovers around 15g daily. We should be eating twice that amount. Why?

There are good reasons. Let’s start from the back and work forward! Bacteria living in the large intestine have the enzymes that we lack to digest fiber. As gut bacteria break down dietary fibers anaerobically (called fermentation), they also use nitrogen sources present in the lumen of the gut (ammonia and urea) to make their own proteins. Some of that nitrogen comes from enzymes and mucins which help digest food and protect the intestine. Eating more fiber leads to an enlargement of the gut microbiome which can sequester nitrogen into bacterial proteins, reducing the amount of nitrogen which has to be excreted via the kidney.

High fiber diets do not compromise small intestinal protein absorption but it does increase small intestinal output to promote colonic fermentation. In a meta-analysis of 14 trials, Chiavaroli and colleagues report that fiber supplementation significantly reduces serum urea and creatinine concentrations.

In short, by eating more dietary fiber, we can help our liver and kidneys maintain normal serum creatinine and urea concentrations. By stimulating bacterial growth and sequestration of nitrogen, colon cancer risk may be reduced. The media daily dose used in the 14 feeding trials was 27 grams. The 2010 Dietary Guidelines recommend that adults eat 14 grams of dietary fiber per 1,000 calories. Assuming certain caloric requirements, this means women and men should consume 25 and 38 grams/d, respectively.  

Most people eat less than half of their requirement. We should eat more dietary fiber. Why? Dietary fiber is important for the health of our intestinal tract, liver and kidneys.

Main Citation

Chiavaroli L, Mirrahimi A, Sievenpiper JL, Jenkins DJA, Darling PB. Dietary fiber effects in chronic kidney disease: a systematic review and meta-analysis of controlled feeding trials. 2014 EJCN doi: 10.1038/ejcn.2014.237

Other Citations

King DE, Mainous III AG, Lambourne CA. Trends in dietary fiber intake in the United States, 1999-2008. 2012 J Acad Nutr Diet doi: 10.1016/j.jand.2012.01.019

McBurney MI, Reimer RA, Tappenden KA. Short chain fatty acids, intestinal adaptation, and nutrient utilization. In Dietary Fiber in Health and Disease, 1997 doi: 10.1007/978-1-4615-5967-2_15

Lien KA, McBurney MI, Beyde BI, Thomson AB, Sauer WC. Ileal recovery of nutrients and mucin in humans fed total enteral formulas supplemented with soy fiber. 1996 Am J Clin Nutr 63:584-595

McBurney MI, Thompson LU, Cuff DJ, Jenkins DJ. Comparison of ileal effluents, dietary fibers, and whole foods in predicting the physiological importance of colonic fermentation. 1988 Am J Gastroenterol 83(5):536-540

McBurney MI, Van Soest PJ, Jeraci JL. Colonic carcinogenesis: The microbial feast or famine mechanism. 1987 Nutr Cancer doi: 10.1080/01635588709513937