You don't know crap:the science of yogurt

When I went home for spring break, I rediscovered yogurt. My mother usually stocks the stuff when it's on sale and although I sampled it occasionally, I generally avoided the Fruit on the Bottom variety, particularly peach.

I hate peach.

But this break, mommy had two new lovelies in the fridge: Yoplait Whips! and Activia. Yoplait Whips! are by far my new favorites: light, fluffy and full of flavor.

Activia, on the other hand, I found a bit sweet for my taste buds. But it had the alluring arrow pointing downstairs, and the label "Bifidus Regularis," so I figured it was some weird yogurt mold and I just can't resist eating something gross.

Turns out I was in for another extraordinary experience: perfectly mobilized bowels!

Activia prides itself on being the only yogurt containing a particular culture of bacteria: Bifidus Regularis, which is actually only a trade name created by the Dannon specialists (Regularis is not the real species name).

The scientific name is Bifidobacterium animalis DN-173 010. It is a subspecies within the genus Bifidobacteria, which is one of the main branches of bacteria that run around in your colon.

Bifidobacteria are Gram-positive, anaerobic rod-shaped bacteria. Along with Lactobacilli - another bacterium found in the gut - Bifidobacteria help break down ingested carbohydrates, and produce organic compounds such as lactic acid, acetic acid and hydrogen peroxide.

In doing so, they decrease the pH of the intestines and prevent growth of other harmful bacteria, all the while helping to get more energy from your food and speeding up intestinal transit.

Activia is special because it's not available in jars. Usually you can't just walk into Charles Street Market and ask Miss D for some Bifidobacterium animalis DN-173 010 because you're constipated. But Activia makes it available in little cups.

Bacteria don't perform their allotted functions, such as assisting in digestion, unless they're alive.

Many of them have a too-short shelf-life or won't make it through the powerful acidity of your stomach.

Bifidus Regularis survives the trip through your GI tract and arrives in the intestines as a live culture, where it can get to work.

Activia doesn't say all this on the container - it would take up a fair amount of space.

Instead, they emphasize the thing that Activia is known for: regulating your bowel movements.

For a healthy adult, food goes in your mouth, over the epiglottis, down the esophagus and into the tummy, then gets sloshed around with pepsin and HCl and then keeps moving on through the duodenum.

It then travels through the rest of the small intestine, then the large intestine, the rectum, the anus and then, hello sewage.

This should take under 72 hours, or else you must be constipated.

This intestinal transit is affected by the food you eat, your gut flora, your stress levels and other environmental factors, including your age and gender (transit time increases with age, and is generally longer in women).

Having bad bowel movements is bad. It could mean you're sick, you're not eating well, or the creepy-crawlies in your GI tract are sick.

If your GI crawlies are feeling a bit under the weather, Activia will help them help you poo.

The scientists at the Activia labs have noted speedier intestinal transit in studies where volunteers ingested fermented milk with or without B. animalis in double-blind experiments. Those that ingested the bacteria were found to have reduced total colonic transit time by 21 percent.

So Activia helps you digest faster, reduces the bad effects of constipation and increases your nutrient uptake.

Ironically, the Activia scientists don't yet know why it does this, they just know that it does it. But they do hypothesize.

Clinical evidence has shown consistent improvements in intestinal transit time with continued ingestion of Activia. Bifidobacterium animalis DN-173 010 does something in between the mesenteries to make digestion easier and pooping smoother and more regular.

If you have intestinal problems, try the Activia two-week challenge.

Studies are showing that in less than two weeks your body may have a replenished Bifidus population, or at least that you'll be squatting regularly. For the diabetics and dieters, try Activia Light or Plain, with fewer carbs and calories.

And for those of you with satisfactory bowel movements, try Yoplait Whips!