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Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a variety of anaemias. Normally the human gastrointestinal tract digests and absorbs dietary nutrients with remarkable efficiency. A typical Western diet ingested by an adult includes approximately 100 g of fat, 400 g of carbohydrate, 100 g of protein, 2 L of fluid, and the required sodium, potassium, chloride, calcium, vitamins, and other elements. Salivary, gastric, intestinal, hepatic, and pancreatic secretions add an additional 7–8 L of protein-, lipid-, and electrolyte-containing fluid to intestinal contents. This massive load is reduced by the small and large intestines to less than 200 g of stool that contains less than 8 g of fat, 1–2 g of nitrogen, and less than 20 mmol each of Na+, K+, Cl–, HCO3–, Ca2+, or Mg2+. If there is impairment of any of the many steps involved in the complex process of nutrient digestion and absorption, intestinal ''malabsorption'' may ensue. If the abnormality involves a single step in the absorptive process, as in primary lactase deficiency, or if the disease process is limited to the very proximal small intestine selective malabsorption of only a single nutrient may occur. However, generalized ''malabsorption'' of multiple dietary nutrients develops when the disease process is extensive, thus disturbing several digestive and absorptive processes, as occurs in coeliac disease with extensive involvement of the small intestine. ==Classification== Some prefer to classify malabsorption clinically into three basic categories:〔Gasbarrini G, Frisono M: Critical evaluation of malabsorption tests; in 〕 # selective, as seen in lactose malabsorption. # partial, as observed in abetalipoproteinaemia. # total as in coeliac disease. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Malabsorption」の詳細全文を読む スポンサード リンク
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