Rye bread and other rye-products can improve bowel function and prevent constipation. This is linked to the high dietary fibre content of rye. Arabinoxylans are slowly and only partly fermented by bacteria residing in the large intestine. Fructans, β-glucans and resistant starch are fermented in the upper part of the colon. Cellulose and lignin are highly resistant towards microbial breakdown. EFSA has accepted a health claim for rye fibre to improve bowel function.
The preventive effect of rye fibre on constipation is due to the increased fecal weight, softer feces, shorter intestinal transit time and increased stool frequency. The unfermentable residue maintains its water-holding property, which is the main reason for the increase in fecal weight.
In addition, intake of rye bread decreases the levels of certain enzymes and toxic compounds which reduce fecal pH and increase the concentration of butyrate and other short chain fatty acids. In vitro studies suggest that rye fiber may also increase the number of bifido-bacteria in the colon.
Rye foods appear to be more effective in overall improvement of bowel health than whole-wheat and low-fiber foods. High-fibre rye bread is recommended in the treatment of constipation.
People with celiac disease cannot tolerate rye due to its secalin content. Secalin is a part of gluten, that causes the immunologic reaction in the small intestine of celiac disease patiens. Rye fibre, especially fructan, may cause functional gastrointestinal symptoms for people with irritable bowel syndrome. Since processing decreases the fructan content, these symptoms may be reduced my freezing or toasting rye bread before consuming it.
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