derived from fructans and xylans are one well documented example of prebiotics. Resistant starch from starchy foods are also well documented prebiotics and have historically been the highest source of prebiotics in the diet, as 4-10% of starch in mixed diets has been shown to reach the large intestine. One study reported that individuals consuming a traditional diet in Africa consumed 38 grams of resistant starch/day. Endogenous An endogenous source of prebiotics in humans is human breast milk, which contains oligosaccharides structurally similar to galactooligosaccharides, referred to as human milk oligosaccharides. human milk oligosaccharides were found to increase the Bifidobacteria bacterial population in breastfed infants, and to strengthen the infant immune system. Furthermore, human milk oligosaccharides help establish a healthy intestinal microbiota composition in newborns. Exogenous Indigestible carbohydrate compounds classified as prebiotics are a type of fermentable fiber, and thus can be classified as dietary fiber. However, not all dietary fiber can be classified as a prebiotic source. In addition to the food sources highlighted in the following table, raw oats, unrefined barley, yacón, and whole grain breakfast cereals are also classified as prebiotic fiber sources. The predominant type of prebiotic fiber may vary according to the food. For instance, oats and barley have high amounts of beta-glucans, fruit and berries contain pectins, seeds contain gums, onions and Jerusalem artichokes are rich in inulin and oligofructose, and bananas and legumes contain resistant starch. While there is no broad consensus on an ideal daily serving of prebiotics, recommendations typically range from for general digestive health support, to or more for those with active digestive disorders. Given an average serving, below are the amounts of prebiotic foods required to achieve a daily serving of prebiotic fiber: Research Preliminary research has demonstrated potential effects on calcium and other mineral absorption, immune system effectiveness, bowel acidity, reduction of colorectal cancer risk, inflammatory bowel disease (Crohn's disease or ulcerative colitis), hypertension and defecation frequency. Prebiotics may be effective in decreasing the number of infectious episodes needing antibiotics and the total number of infections in children aged 0–24 months. No good evidence shows that prebiotics are effective in preventing or treating allergies. While research demonstrates that prebiotics lead to increased production of short-chain fatty acids (SCFA), more research is required to establish a direct causal connection. Prebiotics may be beneficial to inflammatory bowel disease or Crohn's disease through production of SCFA as nourishment for colonic walls,