Maltose Intolerance

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Fermentation of Grain by Yeast Releases Carbon Dioxide Which rises the Dough. Courtesy Johnson Mathey Catalyst

Bread is a Major Source of Maltose. Courtesy Johnson Mathey Catalyst

What Is Maltose Intolerance?

Maltose intolerance is an enzymopathy (enzyme failure) characterized by inability of the gut to properly break down maltose sugar molecules in food due to low maltase enzyme activity of the small intestinal lining.

Q: What is maltose and maltase?

A: Maltose is a double sugar made up of two molecules of glucose and is derived from starch. Maltase is the enzyme required to digest or release glucose from maltose. Maltase is produced in the microscopic brush border (microvilli) at the base of villi.

Here’s what happens when maltose is not digested:

  • Undigested maltose cannot be absorbed into the body but remains inside the small intestine where it acts osmotically to draw an unnatural amount of water from the body into the intestine which produces diarrhea.
  • Additionally, normal gut bacteria ferment the abnormal abundance of unabsorbed maltose, thereby generating an abundance of short-chain fatty acids and hydrogen gas which result in bloating and pain.1
  • Positive response to a breath hydrogen test (BHT), involving 1 – 3 hours of time post ingestion of maltose test dose, signifies malabsorption in the small intestine and fermentation in the colon. If BHT is positive before 60 minutes, the result implies bacteria is abnormally present in the small intestine, causing fermentation there.

What Is Maltose Intolerance In Celiac Disease and/or Gluten Sensitivity?


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  1. Krause’s Food, Nutrition, & Diet Therapy. 10th Edition. Kathleen Mahan, Sylvia Escott-Stump. 2000. W.B. Saunders Company. []