What is normal gas?

It's long been suspected that runners--even moderate-intensity, recreational middle distance runners--are more prone to intestinal gas than average, non-running adults. GI symptoms affect up to 50% of all marathoners; it's widely understood that under the biochemical and biomechanical stresses associated with certain types of exercise, the integrity of the GI mucosal block can become damaged, leading to an uptake of toxic substrates. But although this can and often does cause bloating and gas formation, how much is normal, and what can be done to treat it?

For starters, it's important to understand that the average adult releases one to three pints of intestinal gas daily. Releasing gas 10 to 20 times a day is considered average. Most of this occurs without our knowledge. Some people are simply more sensitive to the presence of gas or less tolerant of its effects.

For runners, bloating, cramps, side ache, and flatulence are among the most common symptoms. But a study of over 600 athletes conducted by the Department of Medical Physiology and Sports Medicine at Utrecht University in the Netherlands found that, while distance running--as opposed to cycling or other forms of exercise--is indeed associated with problems of the lower GI tract, these are significantly related to the frequency of gas occurrence during nonexercise periods, as well as the runner's age and diet. (Cyclists are more prone to upper GI problems such as nausea, belching, and heartburn.) It's not always running that causes the problem, though it may exacerbate it.

The two main sources of gas are, in fact, swallowed air and the breakdown of food in the intestine. We swallow more air if we eat too quickly, gulp down fluids, or drink carbonated beverages. Normal burping is caused by air we swallow while eating and usually ceases within an hour of finishing the meal. Chronic burping is caused by constant, unconscious air swallowing, often from anxiety (hyperventilating increases the amount of air we swallow, thereby increasing gas).

Excessive gas is seldom hazardous. It is unpleasant, however, and several strategies can be used to reduce it. One of the most effective means for reducing gas is to remind yourself to eat and drink more slowly.

The severity of symptoms depends in part upon how fast your digestive system moves. The resident bacteria in the lower bowel produce gas as they break down foods not fully digested by enzymes in the upper GI tract. Changing your diet can help; unfortunately some of the healthiest foods are the biggest gas producers. One major gas producer is raffinose, a complex sugar found in vegetables such as cabbage, broccoli, brussels sprouts, asparagus, and some whole grains. Peas and beans contain starches and fiber that can cause problems as well. Rice is the only starch that doesn't create gas. Fish, chicken, and most meats also produce little gas. If you are lactose intolerant, you will produce gas by eating dairy products, as the undigested lactose makes its way to the gas-producing bacteria in the lower GI.

Myriad products lay claim to helping reduce the gas caused by eating certain foods. Listed here are a few of the more effective. Alpha-galactosidase, aka Beano, reduces gas as it breaks down gas-producing sugars in beans and other vegetables. Activated charcoal pills, though they may react with certain prescription medications, are another option for reducing gas formation. Lactase (such as Lactaid, Dairy Ease, and Lactrase) helps digest foods that contain lactose. Probiotics containing the bacterium L. plantarum, such as those found in yogurt, may reduce gas formation as well, though they can cause gas initially. Pepto-Bismol primarily reduces gas odor.

Beans (whether black, kidney, or pinto) contain great amounts of protein, iron, fiber, B vitamins, potassium, and magnesium. They are inexpensive, have little fat, and may reduce the risk of heart disease, hypertension, and even cancer. For these reasons, it's worth keeping beans in your diet. To reduce the gas they cause, try soaking dry beans overnight or boiling for two minutes and letting them stand for an hour before cooking in fresh water.

(Am. J. Gastroenterol, 1999, Vol. 94, No. 6, pp. 1570-1581; Harvard Women's Health Watch, 2005, Vol. 13, No. 1, p. 4-5)