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.
Secondly, 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
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
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
The study has been published in
the Nutrition Journal.