Simple sugars, or simple carbohydrates, are sweet-tasting compounds that provide you with energy. They're chemically very similar to starches--both are carbohydrates--but simple sugars are much smaller molecules than starches. In biochemical terms, they're also known as monosaccharides and disaccharides, names that provide structural information about them.
Carbohydrates
Carbohydrates are one of the three macronutrient compounds. Macronutrients provide you with energy and also provide building blocks for larger molecules--the other macronutrients aside from carbohydrates are proteins and fats. While there are many kinds of carbohydrates, the three most important from a nutritional perspective are broadly called sugars, starch and fiber. Sugars, simple sugars and simple carbohydrates are three different names for the same kinds of compounds; they're much smaller than complex carbohydrates, meaning starch.
Sugar Chemistry
All carbohydrates are made up of smaller building block molecules called monosaccharides, where the word monosaccharide means single sugar unit. In their book "Biochemistry," Drs. Reginald Garrett and Charles Grisham explain that simple sugars consist of one or two monosaccharide units, while complex carbohydrates consist of many, all chemically bonded together. Some of the most common monosaccharides are glucose, fructose--fruit sugar--and galactose, which is one of the components of milk sugar.
Digestion and Absorption
Your intestine can absorb monosaccharides, but not disaccharides--two monosaccharides bonded together--or polysaccharides, which are made up of many monosaccharides. To absorb the monosaccharides in larger molecules, you have to separate them chemically through digestion. This process is actually very rapid; the rate at which you absorb monosaccharides you consume isn't much faster than the rate at which you absorb the monosaccharides from disaccharide and polysaccharide sources, explains Dr. Lauralee Sherwood in her book "Human Physiology."
Types of Simple Sugars
Many of the compounds you eat on a regular basis are simple sugars. For instance, glucose is a component of many foods including fruit, honey and sweetened foods. You eat fructose when you consume fruit. The disaccharide sucrose, or table sugar, consists of glucose and fructose chemically bonded together. Lactose, or milk sugar, is glucose and galactose. Maltose, or malt sugar, is made up of two glucose units.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
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