The colonic mucosa is unable to nourish itself from the blood. Instead, its nutritive demand must be met from the lumen, where different nutrients, short-chain fatty acids, amino acids, polyamines, growth factors, vitamins, and antioxidants are produced by a nonpathogenic (commensal, so-called "protective" probiotic) flora. The substrates for the production of nutrients are usually referred to as prebiotics, which consist mainly of ingested fibers and complex proteins (colonic food), but may also include necrotic mucosal cells, mucus, gastrointestinal (GI) secretions, and bacteria (as well as yeasts broken down by the bacteria). A characteristic common to all foods destined for the colon--colonic foods-is that no enzymes in the small intestine are capable of breaking them down. It is recommended that a minimum of 10% of ingested calories and about 20% of the food volume should be colonic food. The probiotic flora is today often found deficient, especially in industrialized nations. Studies have shown that Lactobacillus plantarum can preserve key nutrients, vitamins, and antioxidants; eliminate toxic components from food; protect food from decay; and eradicate pathogens such as Enterobacteriaceae, S. aureus, and enterococci from fermented food. In addition, it has demonstrated effectiveness over other bacteria in the metabolism of semiresistant oligofructans. L. plantarum-fermented oat given to healthy volunteers significantly reduces the gut content of potentially pathogenic microorganisms (PPMs).