While the popularity of most diet foods -- from cottage cheese in the 1970s to oat bran in the '80s to the plethora of low-fat foods of the '90s -- has waxed and waned, yogurt has endured. Today, yogurt is more popular than ever, with U.S. sales expected to rise 50 percent by 2010. You may have noticed more people eating yogurt, more yogurt ads on TV and in print, and more yogurt varieties on grocery shelves.

What's driving the current yogurt boom is similar to what drives commuters crazy on Interstate 40 weekday mornings: slow transit.

"The number of people with slow transit has grown remarkably," says Michael Neuwirth, spokesman for Dannon Inc., which recently announced its intentions to double production in the U.S. over the next five years. "It's a direct result of poor diet, stress, too little exercise and not enough water."

All those maladies of the modern lifestyle conspire to keep waste matter in the large intestine longer than need be. Waste should take about 24 hours to work its way through the large intestine. If it takes longer than 72 hours, you're officially constipated. But if it lingers between 40 and 72 hours, you're experiencing "slow transit." It's not harmful, it just gives a bloated feeling.

To battle slow transit, yogurt is being infused with a special probiotic that speeds things along.

In January 2006, Dannon introduced a new yogurt called Activia. In addition to the basic LB (Lactobacillus bulgaricus) and ST (Streptococcus thermophilus) bacteria, Activia includes a probiotic called Bifidus Regularis, the goal of which is to unclog the slow transit traffic jam. In its first year, Activia recorded sales of $100 million.

Packaged Facts, a New York market research firm, predicts such regularity-enhancing products will drive the yogurt market in the next three years. In particular, a liquid yogurt form called "probiotic shots" is expected to see sales grow from $19 million in 2005 to nearly $570 million in 2010.

"We're bullish on probiotics," Neuwirth says.

"Yogurt sales [are] at an all-time high," according to an analysis by Packaged Facts. Sales of all cultured dairy products approached $10 billion in 2005, the latest year for which figures are available and they're expected to grow to $15.4 billion by 2010.

It's about probiotics

Nancy Long is bullish on probiotics, too. She sees a danger in a growing dependence on antibiotics to treat illness, killing good bacteria along with the bad.

As a quick tutorial, she parses the terms antibiotic -- "against life" -- and probiotic -- "for life."

"Anytime you use an antibiotic, you need to replace the good biotics killed with a probiotic," says Long, who with husband Steve owns Harmony Farms, a natural food store in North Raleigh.

The "friendly" biotics are also in short supply in our system, says Long, because we don't eat enough raw food. Cooking kills a lot of the enzymes that assist in breaking down food, further increasing your likelihood of slow transit.

The problem, says Long, is that not all yogurts are as healthy as they would have you believe. While all yogurts contain helpful live and active cultures initially, some go through a pasteurization process that kills them. Or at least some of them.

"There is no way to tell for sure" if such heat-treated yogurts contain beneficial bacteria, according to the National Yogurt Association. (Some companies heat-treat yogurt products to prolong shelf life or to cut down on yogurt's natural tartness, according to the NYA. Products that don't contain live, active cultures are yogurt-covered pretzels, yogurt-covered candy and certain spreads and salad dressings containing yogurt.)

Next page >