Fermentation is good thing when beer makers coax the flavor from hops.

But when fermentation occurs in your body, it's a subject few people like to broach in polite conversation.

Fermentation causes gas. Gastroenterologist Satish S.C. Rao said some people pass gas as many as 25 times a day -- and that's normal.

"Some foods such as cauliflower, brussels sprouts, dried beans, broccoli, cabbage and bran are not completely digested in the small intestine. When the undigested bits of food reach the colon, they are fermented by the bacteria that live in the colon, causing gas," according to the American Gastroenterology Association.

How can you avoid excess gas? Experts said exercise helps the body process foods. The AGA suggested avoiding carbonated beverages, making sure dentures fit properly so you're not swallowing extra air all day and cutting consumption of gum and hard candies, which can also force gas into your stomach.

Hy-Vee grocery store's registered dietitian Carrie Nielsen said the key to reduce gas is to control fiber intake. The government's recommended daily serving of fiber is 20 to 35 grams, but Nielsen said most Americans get half of that.

If you try to boost your fiber intake too quickly, excess gas is often the byproduct. For more on foods that can cause gas and ideas to control it, check out the slideshow:

Slideshow: Gas-Fighting Foods