CHAPTER 13

THE GUT—

Intestinal Digestion and Absorption of Nutrients

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Napoleon once famously declared that an army marches on its stomach. The same can be said of endurance athletes—but the marching is replaced by running, biking, swimming, and other physical activities.

 

 

 

Complaints of intestinal distress probably affect more than half of all endurance athletes. In my experience, another 25 percent have functional intestinal problems that produce little or no overt signs or symptoms. Any of these problems can affect training and especially competition, and often occur at rest as well, influencing a person’s nutritional state. This problem is not only one of comfort, but an indication that the intestines—also called the gut—may not be functioning properly. If this is the case, one may be unable to obtain all the nutrients from one’s diet. A faulty gut can also have a negative impact on immune, muscle, and brain function.

A better understanding about the gut will help correct many intestinal problems and provide more nutrients—and energy—for endurance. The main function of the gut is digestion of food and absorption of nutrients. Most people are well aware of these activities, but the gut is also home to most of the adult immune system: it assists the liver by eliminating toxins, it produces vitamins and hormones, and it has an extensive nervous system of its own. The gut is also in constant communication with the brain. All these areas can become disturbed when the gut is under stress, such as from poor digestion. For example, even if you eat the right foods, if they’re not properly digested and the small intestine does not absorb the nutrients, nutritional imbalances can occur due to malabsorption. This could create a problem identical to those associated with not eating the right foods. Or, a poor functioning gut can reduce immune function, leading to more colds, flu, and other illness.