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Hummingbirds rely on the carbohydrates in nectar to maintain a high speed metabolism.
During digestion, polysaccharides must be broken down into simple sugars before absorption can take place. Indigestion occurs when when the body cannot convert a polysaccharide into monosaccharides. The undigested sugar remains in the digestive tract, feeding resident bacteria. In turn, the bacteria grow in numbers and create gas and indigestion. For humans, dietary carbohydrates are not essential to life.