Q: I try to eat a healthy diet -- lots of whole grains, vegetables and fruits, but it's causing me to have a lot of flatulence. Any suggestions?

A: Flatulence (intestinal gas) is normal. It's a by-product of eating many of the foods we consider healthy sources of vitamins, minerals and fiber. But I completely understand your desire to keep it controlled.

Most intestinal gas is made up of odorless vapors. The unpleasant smell comes from traces of sulfur-containing gases produced by bacteria that live in the large intestine (colon). These microorganisms break down foods, especially carbohydrates, that aren't fully digested by enzymes in the small intestine.

One major gas-producer is raffinose. This is a sugar found in vegetables such as cabbage, asparagus and broccoli. It's also in some whole grains.

Some starches may also cause trouble. This includes potatoes, corn and wheat. It also includes soluble fiber found in oat bran, peas, beans and fruit.

It's interesting, but rice doesn't contribute to gas.

Some people can't digest lactose, the natural sugar found in milk products. So they might develop gas when they eat lactose-containing foods.

Some people can't tolerate fructose, which is in fruits, vegetables and many commercial drinks. Other possible culprits are the sugar substitutes that are used so much today in sugar-free foods and drinks.

You won't be able to stop the gas, but you can reduce it. Keep a diary of the foods you eat. Then eliminate them one at a time to figure out which ones may be causing your symptoms. This way, you may not need to stop eating all of your high-fiber, healthy foods.

Several over-the-counter drugs help with flatulence. Products containing simethicone (Maalox, Mylanta Gas, Gas-X, to name a few) break up gas bubbles in the colon. Beano contains alpha-galactosidase, an enzyme that helps metabolize certain complex carbohydrates. Bismuth subsalicylate (Pepto-Bismol and generic equivalents) may reduce the unpleasant odor of gas.

(Howard LeWine, MD, is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)

(For additional consumer health information, please visit http://www.health.harvard.edu.)

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