Many products on the market are advertising "probiotics" -- beneficial bacteria for digestion.

Now, with the sales of probiotic products soaring, a new health fad is emerging -- something called "prebiotics."

"The difference is that the pro-biotic is the actual bacteria," said gastroenterologist Dr. Brian Bressler. "The pre-biotic is the food to promote the growth of the good bacteria."

Everything from yogurts to snack bars -- and even some baby formulas -- advertise the good bacteria among their ingredients.

But pre-biotics are also being added to products like breads, cereal, and bottled water. And pro-biotic supplements usually have pre-biotics too.

"I think that we need to study the benefits of pre-biotics more than we already have. I think that there's a lot of good that can come out of taking pre-biotic therapy," said Dr. Bressler.

Patients with irritable bowel syndrome, Crohn's disease, and colitis benefit from taking pro and prebiotic supplements.

"The most beneficial thing for patients about it is that it's very cheap and potentially it has a very durable effect," said Dr. Bressler.

But if you don't have digestive problems, prebiotics won't make a difference, he said.

"If you're feeling well, you don't need to take bacteria, and for that matter taking any of these supplements is not going to offer any benefit to you," said Dr. Bressler.

Prebiotics are now being added to many other foods such as cereals, low-fat foods, even drinks.

Some prebiotics to look for on the labels include Inulin, oligo-fructose or fructo-oligosaccharides and lactulose.

Lactulose can also be bought separately on drug store shelves as a natural remedy for constipation. North Americans consume about one-third fewer prebiotic substances than Europeans. Ongoing use of prebiotics hold a lot more promise in helping to support the continued growth of good bacteria in our intestinal tract. Another benefit of breast feeding your baby is to help establish the start of good bacteria in their little intestinal tracts

With a report from CTV British Columbia's Dr. Rhonda Low.