The idea of willfully introducing any bacteria into our foods would usually churn our stomachs. But that’s what we do every time we scoop out a spoonful of yogurt and eat it. And not only do these live organisms not affect us, they actually make us thrive. Scientists attribute yogurt’s benefits to the ability of these live and active cultures (LAC), or probiotics, to create an acidic environment that inhibits the formation of harmful bacteria. In effect the bacteria in yogurt obliterates any foreign nasties lodged in your gut—the kind that can lead to chronic or acute diarrhea. In fact, studies have shown that feeding yogurt to children and adults with diarrhea will speed recovery.

Yogurt is even beneficial to those who are lactose intolerant. These people can’t digest milk-based products because they lack the enzyme “lactase” which breaks down milk’s form of carbohydrate. But yogurt actually produces the lactase enzyme during fermentation, making the milk easier to digest and making the benefits of the LAC, calcium, and protein available to them.

The most popular and most recognized cultures you’d find swimming in the yogurts on your supermarket shelves include: Lactobacillus acidophilus, L. casei, L. reuteri and Bifidobacterium bifidum (Bifidus). For example, Activa (a new low fat yogurt introduced by Dannon) boasts the Bifidis Regularis content found in each container. This particular probiotic helps decrease long transit time in the digestive tract. L. Casei found in DanActive has been shown to boost immunity and shorten the duration of infections.

That sounds great to consumers, but how do we know what is really there and if it is indeed helpful. Fortunately, the National Yogurt Association has made things a little easier by designating a voluntary “LAC” label that manufacturers can put on their containers. To achieve LAC label status, the yogurt must contain a minimum number of live cultures in each serving. It also tells you that the product has been kept refrigerated to maintain the health of the probiotics.

Here are some tips for choosing a high-quality yogurt.

• Choose a yogurt with at least 20 percent of the Daily Value for calcium and 5 grams of protein.
• Watch the calories. If a carton contains over 250 calories per serving, it's likely high in sugar or fat.
• Search the label for "live and active cultures"
• If one yogurt doesn’t taste palatable or goes down with difficulty, try another brand with a different probiotic. Everyone reacts differently to different bacteria strains.