Carbohydrates

Carbohydrates

Carbohydrates are sugars that provide the body with energy that is required to carry out daily activities of exercise. Three kinds of carbohydrates exist:  oligosaccharides (disaccharides like sucrose, lactose, and maltose); polysaccharides that contain three or more simple sugars to form starch, cellulose, and glycogen; and monosaccharide (simple sugars like glucose and fructose). The two main types of carbohydrates in food are categorized as simple carbohydrates (sugars) and complex carbohydrates (starches and dietary fiber).

As carbohydrates are taken into the body, they are broken down and used as energy.  When the body does not need to use the carbohydrates for energy, they are stored in the liver and muscles in the form of glycogen.  When the liver and muscle cells cannot store anymore glycogen, it is turned into fat.

The body needs a constant supply of energy to function properly and a lack of carbohydrates in the diet can cause tiredness or fatigue, poor mental function, lack of endurance and stamina, and slow healing.  Carbohydrates are also crucial for proper brain function, heart and nervous system function, and for the digestive and immune systems.  Lastly, fiber, which is a form of carbohydrate, is essential for elimination of waste materials and toxins from the body and helps to keep the intestines disease-free and clean.

People who train for athletic events are constantly depleted of vital macronutrients that are required for energy production.  Of the three main macronutrients, carbohydrate may be the most dependent variable when it comes to energy use during exercise and may therefore significantly influence athletic performance.  During high-intensity exercise, carbohydrate is the main fuel source for muscle contraction via muscle and liver glycogen.  Fat and protein metabolism is also dependent upon the presence of carbohydrate and the nervous system relies exclusively on carbohydrates for energy.  This is why people who exercise a lot need to consume more carbohydrates than non-exercisers.

It is typically recommended that people consume carbohydrates in the complex form (such as whole grains, fruits, vegetables and legumes) in order to obtain sources of fiber, iron (if enriched), and B vitamins necessary for energy metabolism.

As mentioned previously, the USDA recommends that average adults consume 53% of their calories in the form of carbohydrates.  It is also recommended that very athletic endurance athletes consume 65-70% of their calories in the form of carbohydrates and very athletic strength and power athletes get 55-65% of their calories from carbohydrates.

The following is a list of whole grains, the "good" carbs, and refined grains, the carbs that are less desirable.

Source: Fink, H., Burgoon, L., Mikesky, A. (2006).  Practical Applications in Sports Nutrition.  Jones & Bartlett Publishing