It can only be found in milk, including human breast milk, and in some dairy products. Lactose is the only sugar that cannot be extracted from plants.

Maltose may be produced by malting grain. In 2016, the combined world production of those two crops was about two billion tonnes. Sucrose is especially concentrated in sugarcane and sugar beet, making them ideal for efficient commercial extraction to make refined sugar. Honey and fruits are abundant natural sources of simple sugars. Sugars are found in the tissues of most plants. Some other chemical substances, such as ethylene glycol, glycerol and sugar alcohols, may have a sweet taste, but are not classified as sugar. Starch is a glucose polymer found in plants, the most abundant source of energy in human food. Longer chains of monosaccharides (>2) are not regarded as sugars, and are called oligosaccharides or polysaccharides. In the body, compound sugars are hydrolysed into simple sugars. White sugar is a refined form of sucrose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). Simple sugars, also called monosaccharides, include glucose, fructose, and galactose.

Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food.

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