Sarah Everts discusses how digestive health benefits correlate with high levels of good bacteria promoted by unusual carbohydrates added to food. Humans harbor an army of beneficial bacteria in our guts that build essential vitamins, digest plant fibers, and fight the populations of pathogens that also exist in our intestines. To back up such claims, researchers have shown that consuming the oligosaccharides indeed increases populations of beneficial bifidobacteria and lactobacilli in human guts. Some people confuse prebiotics with its food-science sibling, probiotics, which studies how to boost levels of good gut bacteria through inoculation. The best-studied prebiotic molecules are fructooligosaccharides. Also known collectively as inulin, these oligosaccharides are composed of multiple fructose units capped by a glucose unit at the end. When the number of fructose units exceeds four, Gibson explains, human digestive enzymes cannot break down the oligosaccharides, which can then reach the large intestine.