Q&A: Ask the RD

Answer: While prebiotics and probiotics sound very much alike, that one vowel makes a difference. The more recognized probiotics have yogurt makers to thank for their popularity. Probiotics’ role in promoting digestive health has been advertised in numerous celebrity-endorsed advertisements. Consequently, many consumers are aware that probiotics are “healthy” living bacteria that occur naturally in fermented foods. When ingested, probiotics build up the amount of good bacteria found in the colon, serving to eliminate the bad bacteria encountered in the intestine and ultimately improving digestive and immune functions as well as overall health.

Prebiotics share in probiotics’ function of improving digestive as well as overall health, but they go about it a bit differently. Prebiotics are a special form of dietary fiber that cannot be digested and that provides nourishment to the thousands of good bacteria already living in the colon. Think of prebiotics as food and fuel for those good bacteria. On their own, prebiotics improve health by increasing the bioavailability of some minerals, and also by promoting satiety and weight loss, thereby decreasing the risk of obesity.

The name of the dietary fiber responsible for fueling healthy gut bacteria is fructo-oligosaccharide. This prebiotic substance is found naturally in whole grains, root vegetables, whole fruits and legumes. The term whole is important because any refining of the food eliminates this fiber. As a result, processed and packaged foods and juices won’t give you the benefit you may be looking for.

Because prebiotics and probiotics must be consumed in sufficient quantities to make a difference, you will find them sold as dietary supplements and added to some fortified foods. While it’s always best to get your nourishment directly from a food source, if you choose to enhance your intake of pro- and prebiotics by consuming a fortified food, be watchful that it doesn’t contain excess sugar and calories (as sweetened yogurts and icing-topped fiber bars do).

Here’s to your healthy gut!