Runners Nutrition Part 5: Carbohydrates

We are continuing on our nutrition series and here is a recap: The first step to “Good” Nutrition is focusing on what foods you need for optimal performance, instead of focusing on what foods to avoid.

To learn what an endurance athlete needs to eat in order to maximize performance we will focus on two primary objectives:

  • What am I consuming?
  • Why should I consume it?

What am I consuming?  NUTRIENTS

There are six classes of nutrients: water, vitamins, minerals, carbohydrates, fats and proteins. We’re covering carbs in this one.

1. What am I consuming? Carbohydrates
Carbohydrates can be divided into two classes:
1. Sugars and Starches

  • Digested and metabolized for energy (sugars and starches)
  • Sugars found in jellies, jams, fruits, soft drinks, honey, syrups and milk
  • Starches found in cereals, flour, potatoes and other vegetables

2. Fiber

  • Indigestible
  • Found in vegetables, various fruits, breads, cereals, pasta and rice

Carbohydrate is a major energy source for all tissues and crucial source for two: red blood cells and neurons.  The red blood cells depend exclusively on anaerobic gylcolysis for energy, and the nervous system functions well only on carbohydrate.

Carbohydrates exist in three forms: mononsaccharides, disaccharides and polysaccharides. Monosaccharides are simple sugars and are found in fruits, honey, sports drinks, etc. Disaccharides are formed by combining two monosaccharide.

For example, table sugar is called sucrose and is composed of glucose and fructose. Sucrose is the most common disaccharide and is found in cane sugar, beets, honey, sports drinks and maple syrup. Polysaccharides are complex carbohydrates that contain three or more monosaccharides. Polysaccharides can contain anywhere from three monosaccharides to several hundred. The most usable form of polysaccharide is found in starch from corn, grains, beans, potatoes and peas.

After ingestion starch is broken down to form monosaccharides and may be used as energy immediately by cells or stored in another form within cells for future energy needs. Glycogen is the term used for the polysaccharide stored in animal tissue. It is synthesized within cells by linking glucose molecules together. Glycogen molecules are generally large and can consist of hundreds to thousands of glucose molecules. Cells store glycogen as a means of supplying carbohydrates as an energy source.

2. Why should I consume it?  Carbohydrates
During exercise individual muscle cells break down glycogen into glucose (glycogenolysis) and use it as a source of energy for contraction. This also occurs in the liver as glucose is released into the blood stream.

Glycogen is stored in the muscle fibers and in the liver. Total glycogen stores are relatively small and can be depleted in a few hours of prolonged running.  Therefore, glycogen synthesis is an ongoing process within cells.

Diets low in carbohydrates tend to hamper glycogen synthesis, while high-carbohydrate diets enhance glycogen synthesis. Insufficient glycogen stores will result in a decrease in energy efficiency and eventually energy depletion and a loss of willingness of the athlete to continue exercise. Replenishing carbohydrates within a 30 min window after to depletion will allow for super-carbohydrate-absorption. After this 30 min window absorption ability begins to decrease.



Thanks David Martin for your insight on endurance athlete nutrition and letting us use your research. He told us we could glean and share his information, as we’re working to help you guys run faster.

Better Training for Distance Runners by David Martin

 Exercise Physiology by Powers and Howley 331


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