We’ve all seen the commercials and the shelves full of products containing probiotics. Like me, you probably know enough to know that probiotic products are supposed to help your digestive health. But what are they, really, and do they really work?

I got this article from Rodale this morning and it does a great job of laying out the truth about these increasingly popular products. I had no idea the market was so huge. Probiotics bring in $30 billion dollars a year in sales.

Are you being taken for an expensive ride, though?

Gregor Reid, PhD, a professor of microbiology and immunology at the University of Western Ontario, says that more research is needed, but that the government is getting in the way. According to the  Food and Drug Administration regulations, doctors can’t do clinical trials on foods that contain probiotics without first registering them as drugs. If they did that, we’d end up having to get a prescription for our favorite yogurt.

This has held up a lot of research on probiotic foods, which means we have to trust marketers and their sometimes misleading claims.

Many of these products have never been tested in humans,” Reid says. “I’m not saying they’re bad, or that they’re not  useful. But companies are getting away with using probiotics in their products without doing their due diligence, and consumers have no idea which ones to get and what they do.”

So what do we know?

1. Not all probiotics address the same problems. Each strain (there are billions) is different. If you’re trying to treat a yeast infection, it won’t help you to buy a product that contains probiotics that only help with colds. You can treat a yeast infection with products containing Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, but if you’re trying to help your digestion, go for products that contain Bifidobacterium animalis DN 117-001 (the culture used in Dannon’s Activia yogurt).

2. More is not necessarily better. Reid says there are 300 strains of probiotics on the market, but only 20 or so have been adequately studied. Having a long list of probiotics on the label isn’t always a good thing. In fact, some can work against each other, so the wrong combo can render the product useless.

3. Cooking live bacteria kills them. There are pizzas and other foods advertized as having probiotics, but when you heat these foods, you also kill the beneficial bacteria. Skip the probiotics you have to cook to eat.

Dr. Reid is not by any means against eating probiotic products; in fact, he thinks you should get as many as possible into your diet.

His advice is to stick with probiotic-rich whole foods as such as yogurt, homemade sauerkraut and kimchi (not the bottled stuff, though, which has usually been pasteurized, killing all the good bacteria), sourdough bread, and kefir. Also, try to get plenty of foods containing prebiotics, nondigestible carbohydrates that boost the growth of probiotics in your system. You’ll get prebiotics from whole grains, bananas, onions, garlic, honey, and artichokes.

I’m glad I read this article, because I’ve been buying probiotic yogurt without being positive that I was spending (and eating) wisely. I also may have spent more money on products that don’t do anything other than sound good. If you’ve been using probiotics, I’d love to hear how they’re working for you.