Prebiotics are substances that are not digested by the human body but instead nourish beneficial bacteria in the colon. Most prebiotics are carbohydrates—such as oligosaccharides—although some non-carbohydrate compounds may also have prebiotic effects. The most common prebiotics are nutritionally classified as soluble fiber, and many forms of dietary fiber appear to exert at least some degree of prebiotic activity.
Research published in the Journal of Pediatrics (September 2007; Volume 151:293–298) examined the effects of prebiotic supplementation in 97 healthy, non-obese adolescents with an average age of 11½ years. Participants were randomly assigned to receive either a prebiotic supplement (8 grams per day of inulin/oligofructose) or a placebo for one year.
At the end of the study, body mass index (BMI)—a measure of weight relative to height—was lower in the group receiving the prebiotic supplement. The average BMI difference between the supplement and placebo groups was 0.52 kg/m². When researchers analyzed participants with higher calcium intakes (greater than 700 mg per day), the effect was even more pronounced, with an average BMI difference of 0.82
