Q. Is it safe to take probiotics during pregnancy? I've been taking one capsule a day for about a year, and I've found it helps prevent yeast infections. Can I keep taking it?

A. Yes, it's quite safe to continue. It sounds as if you are nutritionally savvy and have been taking good care of yourself before, as well as during, pregnancy. Probiotics are very popular throughout the world, especially in Europe, and their health benefits are gradually being more appreciated here in the United States. Probiotics, or "bowel bugs" as I like to call them, are healthful bacteria that reside in the colon. The most popular probiotic is lactobacillus acidophilus, found in yogurt and other cultured foods (look for the phrase "live and active cultures" on the label).

Here's how probiotics work: The gut is home to billions of bacteria, good and bad. When harmful bacteria take over, they cause a variety of intestinal upsets, such as diarrhea and inflammatory bowel disease (IBD), as well as fungal infections, such as thrush (yeast). Probiotics colonize the intestines with good bacteria and thereby keep the bad bacteria from multiplying. Probiotics are also beneficial in:

Preventing diarrhea following antibiotic treatment. Because antibiotics not only kill harmful bacteria but may kill the good bacteria in the gut as well, diarrhea is a common side effect. When I put children with ear or throat infections on antibiotics, I routinely prescribe probiotics too. The probiotics replenish the good bacteria, and the balance in the intestines is restored. The probiotics should be taken at the start of (or preferably a few days before) antibiotic treatment and for at least two weeks afterward. Studies have shown that probiotics also help protect toddlers and preschoolers against outbreaks of infectious diarrhea at daycare.

Treating colitis. Here's a medical truism: "You're only as healthy as your colon." Probiotics help reduce inflammation of the colon's lining and are now a standard part of the treatment plan for inflammatory bowel disease (IBD).

Making fatty acids. Probiotics convert the fiber in food into healthy fatty acids that nourish the cells that line the intestines. They also help the intestines make short-chain fatty acids, which contribute to the overall health of the body.

Probiotics are available without a prescription in capsule or powder form at all pharmacies and most health-food stores. A brand I recommend to my patients is Culturelle, which has been used in many recent scientific studies.