ulate the acid-alkaline balance in the large intestine and in turn con-
trol the bacteria themselves. Some fatty acids serve as an important
energy source for the cells in the lower intestine. One specific fatty
acid, butyric, may also play a protective role against cancer by main-
taining a low colon pH and directly inhibiting tumor formation.
The process of fermentation also results in intestinal gas (mostly
hydrogen and methane). If there’s too much gas, causing discomfort or
pain, it’s a sign that there’s a problem. Some of this gas is actually
absorbed via the large intestine into the body, and is released through
the lungs. Those individuals with bad breath usually have too much
fermentation or gas from unfriendly bacteria. In any of these instances,
stress, the wrong foods (typically too much carbohydrate) or too little
fiber, among other problems, can be the cause. Antibiotic use, which
kills the friendly microorganisms in the intestine, can also be a cause.
This destruction of the normal bacteria results in a “re-colonization” of
the large intestine with unfriendly bacteria. Yogurt, which contains
friendly bacteria, can be helpful in these situations. Furthermore, eat-
ing foods that contain prebiotics helps promote the growth of healthy
bacteria in the colon, as discussed later in this chapter.
The beneficial effects of fiber on bile (from the liver and gall blad-
der) may also help prevent intestinal cancers. Excess amounts of bile
in the colon may cause normal cells to convert to cancerous ones. By
eating enough fiber and enough variety of fiber, the concentration of
bile in the colon remains lower.
Fiber and Absorption of Nutrients
Another important function of fiber is how it affects the absorption of
nutrients from your diet. For example, fiber in your meal can slow
sugar (glucose) absorption, and lower the glycemic index of that
meal. Remember that the glycemic index is a measure of the blood-
sugar response to certain foods or meals. Fiber-rich foods generally
have a lower glycemic index and when consumed result in less
insulin production. This makes fiber especially important for anyone
with carbohydrate intolerance. Pectins, mucilages, and especially
gums, seem to do this very well.
Absorption of minerals is also influenced by fiber, but in a nega-
tive way. Phytic acid, a natural substance present in the fibers of
114 • IN FITNESS AND IN HEALTH