Although carbohydrates may have a bad reputation, they are a vital part of a healthy diet.

It is important for consumers not to be misled by fad diets that make claims about the unhealthy aspects of carbohydrates, said Janice Hermann, Oklahoma State University Cooperative Extension nutrition specialist.

“Carbohydrates are important because they provide the necessary energy for the body to function and for physical activity,” Hermann said. “When food is digested, carbohydrates and sugars are broken down into single-sugar units. The main single-sugar unit is glucose, which the body mainly uses for energy. The brain and nervous system can only use glucose for energy.”

In the event there is not enough glucose when energy is needed, muscle tissue can be broken down for protein, which is then turned into glucose and used for energy, particularly for the brain and nervous system. This can cause muscle loss.

“Many fad diets call for strict reduction in carbohydrate consumption, but the key is in making wise choices,” she said.

The best sources of carbohydrates include whole grains, vegetables, fruits and beans/legumes. These are complex carbohydrates that also provide needed vitamins, minerals, fiber and a whole host of phytonutrients which have many health benefits.

Hermann said carbohydrates that have been highly processed such as snack foods, bakery items and non-diet carbonated beverages provide calories but are low in fiber and many important nutrients. Reading labels and selecting products with ‘whole grain’ listed as the first ingredient is an important part of maintaining a healthy lifestyle.

“A great way to start the day is with whole grains such as old-fashioned oats or a cold cereal that lists whole grain as the first ingredient,” she said. “Use whole grain bread for toast and sandwiches.” Adding a piece of whole fruit or 100 percent fruit juice can provide ample energy and nutrients to start the day.

Carbohydrates or saccharides with a molecular formula CH 2O are any of a large group of compounds in which hydrogen and oxygen, in the proportions in which they exist in water are combined with carbon. It provides the most easily accessible energy source for your body. The other main sources of energy are protein and fats. However, carbohydrates are efficiently converted into glucose which will be used for energy. Glucose is used directly by the muscles and brain. Excess glucose is stored as glycogen in the muscles. Carbohydrates are also the most abundant biological molecules and fill numerous roles in living things such as the storage and transport of energy (starch, glycogen) and structural components (cellulose in plants, chitin in animals). Additionally, carbohydrates and their derivatives play major roles in the working process of the immune system, fertilization, pathogenesis, blood clotting, and development.

By being converted into glucose, levels of carbohydrates will affect your blood sugar levels. Your blood sugar levels are important because your brain uses glucose from your blood. This explains why people often get depressed and down beat whilst on diets. Carbohydrates come in two forms which are simple carbohydrates and complex carbohydrates. Simple carbohydrates contain naturally occurring sugars such as those found in fruit (fructose) for example. The sugars that make up simple carbohydrates also include table sugar (sucrose) and a variety of syrups. Complex carbohydrates are present in most grain products, vegetables and potatoes. Unlike simple carbohydrates, complex carbs are digested at a much slower rate. As a result of this, the conversion to glucose also happens at a slower rate and your blood sugar levels will not fluctuate as rapidly as they do when digesting simple carbohydrates.

There are four (4) types or classifications of carbohydrates based on a number of sugar units in total chain.

Monosaccharides single sugar units

Three common sugars share the same molecular formula: C 6H 12O 6. Because of their six carbon atoms, each is a hexose.

They are:

• glucose, “blood sugar”, the immediate source of energy for cellular respiration
• galactose, a sugar in milk (and yogurt)
• fructose, a sugar found in honey.

Although all three share the same molecular formula (C 6H 12O 6), the arrangement of atoms differs in each case. Substances such as these three, which have identical molecular formulas but different structural formulas, are known as structural isomers.

Glucose, galactose, and fructose are “single” sugars or monosaccharides. Two monosaccharides can be linked together to form a “double” sugar or disaccharide.

Dissacharides two sugar units

Three common disaccharides:

• sucrose — common table sugar = glucose + fructose
• lactose — major sugar in milk = glucose + galactose
• maltose — product of starch digestion = glucose + glucose

Although the process of linking the two monomers is rather complex, the end result in each case is the loss of a hydrogen atom (H) from one of the monosaccharides and a hydroxyl group (OH) from the other. The resulting linkage between the sugars is called a glycosidic bond. The molecular formula of each of these disaccharides is C 12H 22O 11 = 2 C 6H 12O 6 − H 2O. All sugars are very soluble in water because of their many hydroxyl groups. Carbohydrates provide the bulk of the calories (4cal/gram) in most diets, and starches provide the bulk of that. Starches are polysaccharides.

Oligosaccharides three to ten sugar units

Oligosaccharides and polysaccharides are composed of longer chains of monosaccharide units bound together by glycosidic bonds. The distinction between the two is based upon the number of monosaccharide units present in the chain. Examples of oligosaccharides include the disaccharides mentioned above, the trisaccharide raffinose and the tetrasaccharide stachyose.

Oligosaccharides are found as a common form of protein posttranslational modification. Such posttranslational modifications include the Lewis oligosaccharides responsible for blood group incompatibilities, the alpha-Gal epitope responsible for hyperacute rejection in xenotransplanation, and O-GlcNAc modifications.

Polysaccharides more than ten units

Starches are polymers of glucose. Two types are found:

• amylose consists of linear, unbranched chains of several hundred glucose residues (units). The glucose residues are linked by a glycosidic bond between their #1 and #4 carbon atoms.
• amylopectin differs from amylose in being highly branched. At approximately every thirtieth residue along the chain, a short side chain is attached by a glycosidic bond to the #6 carbon atom (the carbon above the ring). The total number of glucose residues in a molecule of amylopectin is several thousand.

Starches are insoluble in water and thus can serve as storage depots of glucose. Plants convert excess glucose into starch for storage. The image shows starch grains (lightly stained with iodine) in the cells of the white potato. Rice, wheat, and corn are also major sources of starch in the human diet.

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