Chocolate bars, bread and baked potatoes all have one thing in common: carbohydrates. Carbohydrates, shown on nutrition labels as sugars, starches and fibers, are made from molecules called saccharides. The term "saccharide" comes from the Greek word for sweetness because of the characteristic sweet taste of some saccharides. Carbohydrates are an important source of energy for humans.
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Monosaccharides, Simple Sugars
Monosaccharides are commonly known as the "building blocks" of carbohydrates because all carbohydrates contain one or more monosaccharides. The term "monosaccharide" literally means "one sugar." The three major monosaccharides are glucose, fructose and galactose. Glucose is well-known for its role in blood sugar levels and is the main type of sugar the body uses for energy. Glucose is commonly found in plants in the form of starch. Fructose, found in fruit, is sent to the liver to get converted into glucose after it is ingested. The structure of galactose is extremely similar to that of glucose. Galactose is part of the milk sugar molecule lactose and is also converted by the liver into glucose, just like fructose.
Disaccharides, Double Sugars
The term "disaccharide" means "two sugars." Disaccharides are made from two monosaccharides. The three major types of disaccharides are sucrose, maltose and lactose. Sucrose, made from glucose and fructose, is found naturally in sugar beets, maple syrup and sugar cane. Maltose is a combination of two glucose molecules and is not usually found in nature. Maltose forms during starch breakdown in the human mouth. Lactose is formed from glucose and galactose. This disaccharide is commonly found in dairy products like milk. Lactose intolerance occurs when a person's digestive system is not able to digest the bond between the galactose and glucose molecules.
Polysaccharides, Many Sugars
Polysaccharide is the term used for carbohydrates that are formed from more than two monosaccharides. Polysaccharides are also known as complex carbohydrates because they sometimes develop from thousands of monosaccharides. One of the most common polysaccharides is starch. Plants use starch to store carbohydrates, so it can be found in foods like potatoes and beans. Humans store carbohydrates in muscles and in the liver, in the form of the polysaccharide glycogen. Fiber is made up of indigestible polysaccharides. The most common type of fiber is made from cellulose, a polysaccharide that defines the structure of plants. Other types of fiber include mucilage, hemicellulose, gum and pectin.
Carbohydrates on Nutrition Labels
The three types of carbohydrates listed on nutrition labels are sugar, starch and dietary fiber. People counting their carbohydrate intake should take all three types of carbohydrate into consideration. Starch, a polysaccharide, is found in foods such as peas, lima beans, corn, pinto beans, kidney beans, barley and oats. The sugar listed on food labels usually includes monosaccharides such as sucrose and fructose, or disaccharides like lactose. It is important to note that the amount of sugar listed includes both naturally found sugar and added sugar. Fiber, an indigestible polysaccharide, helps keep the digestive system healthy. The American Diabetic Association recommends 25 to 30 grams of fiber each day for healthy adults.