Increasing stool bulk, diluting possible carcinogens present in the diet and decreasing transit time through the colon significantly reduce the risk of colorectal cancer.
It has been long known that dietary fiber helps improve the health of the digestive system. The digestive system is lined with muscles that massage food along the tract from the moment a mouthful is swallowed until the eventual waste is passed out of the bowel through a process called peristalsis. Since fiber is relatively indigestible, it adds bulk to the feces. Soluble fiber soaks up water like a sponge, which helps to bulk out the feces and allows it to pass through the gut more easily.
AdvertisementSecondly, soluble fiber lowers blood cholesterol by binding bile acids and then excreting them. And third, bacterial fermentation of fiber results in the production of short-chain fatty acids, which are thought to have protective effects against colorectal cancer.
In view of this, Anita Fechner and her colleagues at Department of Nutritional Physiology, Friedrich Schiller University of Jena, Germany, conducted a study to compare physiological effects of three legume kernel fibers and citrus fiber on LDL cholesterol in relation to colonic health, especially colorectal cancer.
Seventy-eight healthy volunteers (of which 76 completed the study) in the age group of 20 to 45 years were randomly divided to consume 25g per day of a legume fiber - blue lupin, white lupin and soya, and citrus fiber for two weeks. The dietary fiber intake throughout the interventions was additional to their habitual fiber intake, so the total dietary fiber intake during the study was approximately twice the fiber intake (42.7 to 46.3 g/day).
At the end of run-in (no-treatment period) and intervention, a quantitative feces collection took place and fasting blood samples were drawn.
The findings revealed that-
* The lupin fiber supplementations increased daily fecal dry matter and fecal weight compared to control by 1.76g feces (blue lupin) and 1.64g feces (white lupin) per gram of additional dietary fiber.
* Lupin fibers led to a significantly enhanced formation of short-chain fatty acids.
* Blue lupin fiber decreased fecal pH by 0.27 units and increased primary bile acids-excretion as compared to run-in (no-treatment) period.
* All legume fibers reduced fecal concentrations of total and secondary bile acids.
* Blood lipids were not influenced by any intervention.
From the results the researchers deduced that a daily intake of 25 g legume kernel fiber or citrus fiber over two weeks did not affect lipid metabolism through bile acid-binding in healthy people, but all of them might be able to prevent constipation as they improve fecal consistency and oro-fecal transit time and therefore exert a positive impact on colonic function.
The researchers concluded that 'increasing dietary fiber intake of blue lupin kernel fiber in the range of about 50g per day may in general and, in particular, in predisposed people contribute towards the prevention of colorectal cancer and support medical therapies'.
The study has been published in the Nutrition Journal.