Carbohydrates Power Our Body
What does the word “carbohydrate” mean?
The term carbohydrate was coined long ago as scientists observed a consistent pattern in the chemical formula of most carbohydrates. Not only were they composed of only carbon, hydrogen, and oxygen but also the ratio of carbon to the chemical formula of water (H2O) is typically one to one (C:H2O). Carbohydrate means “carbon with water.” For example, carbohydrates glucose and galactose have the following chemical formula:
C6H12O6 or (CH2O)6
Where do carbohydrates come from?
To create energy-providing carbohydrates from the non-energy-providing molecules H2O and CO2 is a talent limited to plants and a handful of bacteria. In a process called photosynthesis, these life forms are able to couple H2O and CO2 by harnessing solar energy. Along with carbohydrates, O2 is also a product of this reaction:
6 CO2 + 6 H2O à C6H12O6 + 6 O2
Humans are unable to perform photosynthesis and thus we eat plants and plant products such as fruits, vegetables, legumes and grain products to obtain a rich supply of carbohydrates. Beyond plants and their products, milk and dairy are also good sources of carbohydrates. In fact, milk and some dairy products is one of only a few considerable source of carbohydrate from animal foods; honey is another. It should be mentioned that while humans cannot perform photosynthesis, we do possess the ability to make some carbohydrate in our body. However, in order to do so, we must start with molecules that already possess energy. The process is called gluconeogenesis and starts with amino acids (from protein), glycerol (from fat) and lactate (from lactic acid).
Are there different types and classes of carbohydrates?
As you might guess, numerous different kinds of carbohydrates are found in nature. However our discussion will be limited to those carbohydrates found in greater amounts in our diet and those important to our body. The simplest carbohydrates are the monosaccharides, which include glucose (dextrose), fructose, and galactose. Other examples of monosaccharides include xylose, mannose, and ribose, but these may not be as familiar to you. There are over 100 different monosaccharides found in nature and these serve as the building blocks for larger carbohydrates such as disaccharides, oligosaccharides, starches and fibers.
What are monosaccharides and what foods have them?
Monosaccharides are as small as carbohydrates get. Said another way, monosaccharides cannot be split into smaller carbohydrates. All other carbohydrates are made up of monosaccharides linked together. For instance, disaccharides are composed of two monosaccharides linked together. The three disaccharides found in our diet, including their monosaccharide building blocks, are listed below.
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Glucose and fructose can be found in foods either independently or as part of larger carbohydrates. Fructose is what makes honey and many fruits sweet and is used commercially as a sweetener either as fructose or high fructose corn syrup. On the other hand, while some galactose is found in certain foods, it is mostly found as part of larger carbohydrates.
What are disaccharides?
Glucose is one-half of the disaccharides lactose and sucrose and both halves of maltose. Maltose, or malt sugar, may be part of our diet naturally in seeds or alcoholic beverages. Sucrose is derived from the sugar cane plant and the beet, which and the sucrose rich product is called “sugar.” Lactose is the primary carbohydrate found in milk and dairy products. Nutrition scientists often refer to monosaccharides and disaccharides as “simple sugars” because of their relatively small carbohydrate size and their sweet taste. The relative sweetness of simple sugars and compares them to sugar alcohols and artificial sweeteners are presented below.
Table of Relative Sweetness of Sweeteners
What are oligosaccharides and starches?
Monosaccharides not only serve as building blocks for disaccharides but also for some larger forms of carbohydrates as well. The most recognizable larger carbohydrate is starch. Starch is found in varying degrees in plants and their products (e.g. legumes, vegetables, fruits and grains). It consists of large straight and branching chains of the monosaccharide glucose. Some shorter, branching chains of glucose can be found as well as food manufactures will also use these in the production of foods. The short, branching chains used by food manufacturers are often called maltodextrins and is typically derived from the partial digestion of corn starch. In the human diet, we can also find a small amount of carbohydrates, called oligosaccharides, constructed from just a few monosaccharides (three to ten) linked together. More oligosaccharides are being extracted from plant sources and used in foods for different reasons. For instance iso-oligosaccharide or IMO is used in nutrition bar manufacturing to help bar structure as well as provide fiber. Meanwhile a few other oligosaccharides (e.g., raffinose and stachyose) are legendary components of beans, not necessarily for their nutritional value but for their effects within the digestive tract. Plants make starch to store energy kind of like mammals store fat. Plant fibers, on the other hand, are not necessarily stored energy but serve more structural roles for plants. Like starch, fiber also composed of straight and branching chains of monosaccharides, but their monosaccharides building block are not limited only to glucose.
What do carbohydrates do in our body?
Carbohydrates play quite a few roles in the human body, but perhaps none as important as being the most basic energy/fuel source for all human cells. All 60-100 trillion cells in the body will use glucose to some degree. Meanwhile, cells of the central nervous system as well as red blood cells and certain other types of cells will exclusively use glucose (or lactate from glucose) under normal situations. Carbohydrates also provide limited yet readily available energy store called glycogen found mostly in muscle and the liver. As an energy source, carbohydrate provides 4 calories per gram. Carbohydrates are also a modest yet vital component of cell membranes. Certain carbohydrates are also key portions of indispensable molecules. For example, molecules such as DNA and RNA contain the carbohydrate ribose. Ribose is a monosaccharide that can be made in our cells from glucose as well as coming from the diet. Also, very complex carbohydrates called glycosaminoglycans (GAGs) are very important in connective tissue, such as in our joints. The GAGs include chondroitin sulfate and hyaluronic acid, are found in some nutrition supplements targeting joint support.