Initial Posting: 9/14/2014    Last Update: 11/15/2019
Answer: As discussed in detail in the Prebiotics section of the Probiotic Supplements Review, prebiotics (such as inulin and fructo-oligosaccharides or FOS) are plant-based complex sugars that act as food for healthy bacteria (probiotics), promoting their growth in the digestive tract. Two to 6 grams per day of prebiotics are sufficient. This amount can easily be provided by eating certain foods. It can also be provided by supplements -- although, due to the relatively large amount of prebiotic needed, this would require multiple pills, so another form, such as a powder, may be preferable. Some probiotic supplements include a prebiotic, but typically only a small amount (less than a quarter of a gram per pill).
Most of the clinical trials with prebiotics have been with a specific branded ingredient found in certain marketed supplements. For details about this, and for information about the potential benefits and side effects of prebiotics, as well as our tests and comparisons of probiotic supplements that contain prebiotics, see the Probiotic Supplements Review >>