A carbohydrate is a macronutrient that the body converts into glucose, which it then absorbs into the bloodstream for use as energy for cells throughout the body. Carbohydrates fall into one of two categories --- simple or complex --- depending on their chemical structure. Simple carbohydrates include single and double sugars, while complex carbohydrates contain sugar, starch and fiber. Fiber is the only constituent of carbohydrates that do not provide energy, but instead, provide other nutritional benefits.
Sugars
Sugars, or saccharides, are simple carbohydrates and are either monosaccharides are disaccharides. Monosaccharides are sugars that comprise one type of sugar molecule and these include galactose, fructose and glucose. Disaccharides consist of two types of sugar molecules. For example, lactose contains bonds between galactose and glucose, while sucrose consists of bonds between glucose and fructose.
Many foods contain sugars naturally; fruits, for example, contain fructose. However, sugars have no nutritional value, save for the energy they provide once the body converts them to glucose. Therefore, although they increase the caloric value of the foods in which they naturally occur, bolstering their energy yield, they are extraneous as additives. Extra calories, such as those derived from added sugar, substantially contribute to weight gain, so add sugar to foods sparingly.
Starch
Starch occurs most often in complex carbohydrates, such as breads, grains, rice, noodles and vegetables like potatoes and squash. However, some foods that contain starch are stripped of other aspects that render them complex carbohydrates. For example, white flour is made from wheat with the fibrous hull and nutritious wheat germ removed, leaving only the starchy endosperm. Moreover, bread made from such flour usually contains high fructose corn syrup, resulting in a high-caloric food. The FDA does require that manufacturers enrich such bread with essential vitamins, increasing their nutrition. However, it remains most nutritious to eat breads made from flour that contains whole wheat.
Although the body converts starch to glucose, the process by which it achieves this conversion takes longer. This results in more gradual increases in blood sugar, placing less stress on the pancreas and generating less excess glucose. Therefore, although a diet abundant with starch can still result in weight gain, starch is far less conducive to obesity than saccharides. Moreover, most foods in which starch occurs also contain other essential nutrients, rendering meals that contain starch more nutritious. Exceptions usually relate more to preparation rather than the source. That is to say, whereas eating a baked potato could be both satisfying and nutritious, eating potato chips, which contains little more than starch and usually large amounts of sodium and preservatives, is far less healthy.
Soluble Fiber
Soluble fiber occurs only in certain complex carbohydrates, like cereal grains, fruits, legumes and vegetables. Soluble fiber dissolves in water within the body to become a gelatinous substance that absorbs into the bloodstream. Once there, it can effectively reduce cholesterol levels. However, it reduces both LDL and HDL cholesterol, which can be potentially counterproductive. Once filtered from the bloodstream, soluble fiber ferments in the intestine, benefiting naturally occurring bacteria. This both regulates digestion and prevents the proliferation of detrimental bacteria that can cause infection.
Insoluble Fiber
Insoluble fiber occurs in particular complex carbohydrates, including whole wheat, nuts, seeds, fruits and vegetables. This variety of fiber remains intact throughout its entire stay in the body. This slows digestion down, reducing the amount of food required for satisfaction as well as the duration of that satisfaction following the meal. However, once the food passes into the intestines, the insoluble fiber helps quicken the elimination of waste. The result is more complete digestion of a more satisfying meal.
The Bottom Line
There are no "good" or "bad" carbohydrates, as they are essential nutrients that provide energy for somatic cells to function. But ingesting simple carbohydrates can add high amounts of sugar and lead to several health difficulties, including obesity, diabetes, renal complications and vision degeneration. Eating complex carbohydrates is the best way to derive energy from food, but even complex carbohydrates in excess can be detrimental, leading to weight gain and dietary imbalances. The best approach is to balance your carbohydrate intake and you can achieve this by deriving them naturally from foods eaten as part of a nutritious diet. Consult a physician or nutritionist to determine the optimum diet.
References
- MedlinePlus.com: Carbohydrates
- MedlinePlus.com: Carbs
- MayoClinic.com: Diabetes
- "Carbohydrates: The Essential Molecule of Life"; Robert V. Stick and Spencer Williams; 2009
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