What’s behind the success of Dannon’s Activia yogurt? Great ads? Maybe. But the credit really goes to probiotics, the product’s main ingredient. Research shows that probiotics—“friendly” live microorganisms—may regulate your digestive system, protect you from colon ulcers and reduce symptoms of irritable bowel syndrome.

“Diet, illness, aging and stress are all factors that can affect our body’s ability to maintain balance between ‘good’ bacteria and harmful bacteria,” says Mary Ellen Sanders, PhD, a Colorado-based probiotic microbiology consultant. “Since probiotics are similar to the ‘good’ bacteria already found in our bodies, taking certain probiotics can help strengthen your body’s natural defenses by correcting the imbalance and optimizing the function of your immune system.”

Other food manufacturers have become hip to the game and are adding probiotics to everyday foods, such as milk, juice, yogurts and supplements. Sanders suggests trying these products:

Eat DanActive yogurt ($4.49, 3.1 fl oz., 4-pack) or take Culturelle capsules ($7.99, 10 capsules) for immune support.

Drink GoodBelly juice ($3.99, 32 fl. oz.) for irritable bowel syndrome.

Try lemon-flavored BioGaia Probiotic chewable tablets ($32.91, 30 tablets) for overall health.

FYI: Since there isn’t a way to ensure that all products containing probiotics have been clinically tested, Sanders recommends doing your research and sticking to trusted brands.