Digestion and Absorption


Products of Protein Breakdown

Products of Protein Breakdown are short chain fatty acids (SCFAs) that come from the bacterial breakdown of protein or their digestion products (amino acids), in the distal colon. They include isovalerate, valerate and isobutyrate.

Normal protein digestion is generally completed in the stomach and small intestine, thus only small amounts of protein-derived products of protein breakdown are expected to be in the stool. The SCFAs described more robustly in clinical literature, specifically acetate, butyrate and propionate, are produced by bacterial action on carbohydrates and are not included in this discussion.

Potential indications for assessment of products of protein breakdown include patients with:

  • Symptoms of maldigestion and malabsorption
  • Those with increased protein material (such as mucus, intestinal cell turnover, or blood) in the distal colon
  • Note: High protein diets may also increase normal levels

Products of Protein Breakdown are utilized as a contributory diagnostic tool, in a full clinical evaluation. There are no gold-standard or comparator tests for evaluating products of protein breakdown in stool.

Though the relationship between gut health and protein fermentation has not been thoroughly investigated, patients with elevated products of protein breakdown should be evaluated for:

  • Common causes of insufficient protein digestion
  • Excessive protein presenting to the colon
  • Excessive protein intake   


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