Probiotics and Prebiotics: Basics

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Over the past two weeks, we’ve taken a closer look at probiotics, those gut-friendly bugs that hold much promise in keeping us healthy and possibly even preventing illness and disease. Understandably, some people don’t quite have the, uh, “stomach” to think about bacteria actually being good for us. But it’s time to think out of the box a bit and realize that researchers are just scratching the surface in learning about probiotics and their potential for promoting health.

To Take or Not to Take?
Admittedly, the more I read about probiotics, the more tempted I am to take them just to prevent any problems from occurring down the road. It sounds tempting: If a probiotic supplement or probiotic-enhanced food can lower the risk of cancer, fatty liver disease, Type 2 diabetes, and obesity, why NOT take it?

As always, the mantra is: Check with your health-care provider before taking any type of supplement, including probiotics. Probiotics, in general, are safe to take. However, there are always exceptions. For example, some health-care experts advise people who have suppressed or compromised immune systems, such as people with HIV or who are undergoing chemotherapy or radiation, to avoid probiotics. And a study of people with pancreatitis found that probiotics could increase the risk of death (although this was later called into question).

Another pointer: Evidence, thus far, indicates that there are no real negative effects from taking probiotics for most people. But data on safety, and particularly long-term safety, is pretty limited. We also don’t know what the effect of taking probiotics is among people with health conditions.

Choosing a Probiotic
If you’re thinking that a probiotic might help you, first talk it over with your health-care provider, and don’t stop taking any medicine that you’ve been prescribed. Note that probiotics are designated with a genus, species, and strain (remember biology class?). Lactobacillus probiotics are usually abbreviated with an “L,” and they work mostly in the small intestine. Examples include L. rhamnosus GG, L. acidophilus, L. reuteri, and L. bulgaricus. Bifidobacteria work in the large intestine. This type of bacteria is abbreviated with the letter “B”; B. bifidum and B. longum are examples. Saccharomyces boulardii is actually a fungus, not a bacterium, which seems to be helpful in alleviating antibiotic-induced diarrhea and traveler’s diarrhea.

The effectiveness of any probiotic depends on how many live cells it contains. You can look at the “colony-forming unit” or CFU, on the container. Keep in mind that there is no one CFU number that is right for each condition. A reputable brand of probiotic will list the CFU number, the strain of probiotic, the recommended serving size, how to store it, the expiration date, and the manufacturer’s contact information.

Don’t Forget Prebiotics
All this talk about “good” bacteria may sound great, but it’s important not to overlook something else, called “prebiotics.” Prebiotics are essentially food for probiotics (hey, even bacteria need to eat!). Prebiotics help to promote growth and activity of beneficial bacteria, and they are typically found in carbohydrate foods, including:

Oats and oatmeal
Jerusalem artichokes

Prebiotics might also be added to foods (not surprisingly), including yogurt, cottage cheese, granola bars, and even pasta. Prebiotics may be listed in any of the following forms on a food label: inulin, fructo-oligosaccharides, polydextrose, maltodextrin, and lactulose.

Prebiotics may do more than just feed probiotics, however. For example, prebiotics can help the body absorb minerals, lower blood cholesterol, inhibit the growth of tumors in the intestinal tract, and promote overall bowel health.

Prebiotics are not harmful, but they may cause side effects, such as gasiness, bloating, and mild cramping, at least initially. Aim for about 5 to 15 grams of prebiotics each day. You can find prebiotics in supplement form, as well as in the foods listed above. You might also come across a type of supplement called a “synbiotic,” which means that it contains both pre- and probiotics.

Expect to hear and read more about probiotics going forward. Until we know more about them, though, use them cautiously, and talk it over with your health-care team if you think a probiotic supplement could be beneficial for you. For more information, visit the US Probiotics Web site at

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