Pectin is a soluble fiber that is found in most plants, but is most concentrated in citrus fruits and apples. Pectin is obtained from the citrus peels of fruits and apple pulp. Pectin obtained from citrus peels is referred to as citrus pectin. For medicinal purposes, pectin is used in combination with the clay kaolin (hydrated aluminum silicate) for the management of diarrhea. Pectin is also marketed as a nutritional supplement for the management of elevated cholesterol. D-Galacturonic acid is the principal monosaccharide compound that composes pectin. Some neutral sugars are also present in pectin. The D-galacturonic acid residues are linked together by alpha-1, 4 glycosidic linkages. There are different types of pectin. Pectin in which more than 50% of the galacturonic acid residues are esterified is called high methoxyl or HM pectin. Pectin in which less than 50% of the galacturonic acid residues are esterified is called low methoxy or LM pectin. Pectin is a non-digestible polysaccharide. So-called modified citrus pectin is pectin that has been hydrolyzed and otherwise modified to make it more digestible and absorbable.