The first prebiotic fibers you probably encountered in life, were in mother's milk. It's one of the only non-plant sources of prebiotic fibers. From there, your prebiotics would likely have come from grains (wheat, oats, barley and rye are good sources), vegetables (onions, leeks, garlic, asparagus) and fruits (bananas). Other plant sources may have prebiotic fibers, but in much smaller amounts.
Functional Food Fiber
Prebiotic fibers are the soluble part of plant fibers that can be fermented in the gut, to provide short chain fatty acids (SCFA) like butyrate, propionate and acetate. The probiotic bacteria digest the starches in the prebiotics, and generate the SCFAs, which benefit the host (you).The SCFAs are used by the epithelial cells of the gut. Prebiotics have been found to improve gut function and structure.
Prebiotics +/- Probiotics
Unlike prebiotics, the effects of probiotics can be "strain-specific", meaning that one strain of Lactobacillus acidophillus may work differently, or not at all, compared to another strain. Some studies have even shown that subjects getting a prebiotic had better results in butyrate production than the study group receiving the same prebiotic plus a probiotic. Apparently because the probiotic cancelled the effect of the prebiotic. So while prebiotics are non-specific workhorses that provide the energy for all probiotics in residence, adding specific probiotics doesn't always improve the results.
From Cardiovascular To Weight Loss
Fiber has been credited with health benefits ranging from weight loss to cardiovascular improvements. Not only is it affordable and readily available, it can be consumed in generous portions with almost no worries. And very few of us get enough fiber in our diets. All plant fiber sources include both soluble (fermentable) and insoluble (roughage) fibers. Both can absorb water along the way, which is good, and the insoluble fibers provide needed bulk while helping to remove digestive toxins and impurities.