Probiotics are helpful bacteria found in the intestine and gut. They improve immunity and aid digestion, and increasing evidence indicates they help with gastrointestinal conditions like irritable bowel syndrome, says Natasha Kassam, a naturopathic provider with highly rated 8 Hearts Health & Wellness of Portland, Ore.

“When good bacteria are out of balance, bad bacteria hold on and replicate,” she says. “Probiotics are the immune-system superheroes who kick out the bad guys and replenish good bacteria.”

Dietitian Joy Supplee of highly rated Custom Fit Nutrition in Mercer Island, Wash., says probiotics are beneficial to everyone, but they’re essential for those who are susceptible to illness. “About 70 percent of your immune system is in your intestines,” she says.

Experts say Lactobacillus is the most common and, according to several studies, the most helpful probiotic. Yogurts and fermented vegetables, soy and dairy products are packed with probiotics, but Kassam adds dietary supplements are a more reliable source.

“Usually, you want to get a probiotic that has anywhere from 1 to 10 billion colony forming units in a variety of strains,” Kassam says. “Each species and strain helps in a different way, so you want to make sure that you are getting the kinds you need.”

She recommends consulting a doctor first, but quality over-the-counter supplements are typically refrigerated and cost between $30 and $50 per 60-capsule bottle.

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