Since mannose is natural, the United States Food and Drug Administration classifies the saccharide as a nutritional supplement rather than a drug. Yet, it is sometimes prescribed by doctors as a form of medical treatment. For instance, mannose, which is also marketed under the names seminose and carubinose, is often recommended for those suffering from urinary tract infections caused by Escherichia coli, a common gut bacteria. The reason mannose is an effective treatment for such infections is that the sugar coats the bacterial cells and makes them less inclined to stick to the lining of the urinary tract so that they may be readily flushed away with urine. Moreover, since mannose is absorbed in the upper gastrointestinal tract, the beneficial E. coli of the lower intestines are not affected.