Runner's Guide to Nutrition
by Greg McMillan, M.S.
Nutrition is rapidly becoming the next frontier that many scientists, coaches and athletes are exploring and manipulating for improved distance running performance.
This article will discuss the basic principles of good nutrition with a detailed examination of the primary nutrients (carbohydrates, fats, proteins and water) as well as the recommendations made by exercise scientists and nutritionists as to the proper amounts of each nutrient that should be included in your diet. I note right up front that nutrition, like training, is very individual. You need to experiment and listen to your body to find the right mix of nutrients and the timing of your nutrient intake to see what best fuels your running.
Vital to the improvement of your diet is evaluating (1) the amount of calories that you obtain per day (called your total daily caloric intake), (2) the proportion of these daily calories that are supplied by carbohydrates, fats and proteins. Armed with this information, you can evaluate your nutrient intake and even adjust your caloric intake to acheive your weight loss goals. This evaluation will also reveal your dietary strengths and weaknesses, enabling you to compare your diet to what the diets recommended by various experts. To help you, we've created the Runner's Nutrition Calculator.
And finally, you’ll learn how to use your calculated nutritional needs to analyze your diet. This analysis will allow you to correct your nutritional weaknesses to ensure that you are eating properly, thus optimizing your chances at distance running success.
The Primary Nutrients
There are four substances that the body requires in large quantities in order to function properly. These four substances are called the primary nutrients and include (1) carbohydrates, (2) fats, (3) proteins and (4) water.
Carbohydrates
Carbohydrates, also known as sugars, are the primary nutrient and dietary source of quick energy for distance runners. Experts recommend that runners’ diets consist of 50 to 70 percent carbohydrate. The zone diet recommends 40 percent and a low-carb diet reduces this even further.
The sole purpose of carbohydrates in the body is to provide energy. The standard unit for the energy our bodies use is called a calorie. Each gram of carbohydrate provides four calories.
The carbohydrates that we eat can be classified as either simple or complex. Simple carbohydrates are the most basic form of sugar and consist of only one or two molecules. These simple sugars include among others, glucose, fructose and sucrose. Examples of foods containing this type of carbohydrate include candy, fruit, milk, sports drinks and energy gels.
Since simple carbohydrates consist of only one or two molecules, they are rapidly absorbed into the bloodstream. While this fast absorption is great for providing a quick “shot” of energy during periods when the blood sugar level is low, it also induces what exercise scientists call an insulin response.
Insulin, a hormone produced by the pancreas, facilitates the removal of sugar from the bloodstream and places it in the cells. As a result, the blood sugar level is returned to a low level resulting in both decreased energy and performance. Athletes have to be careful with their intake of simply sugars to avoid this spike and fall in blood sugar. The typical American diet is full of simple sugars which may be a contributing factor in the epidemic in diabetes. We’ve all experienced a “sugar crash” so you’re well aware of the potential for this to interfere with your everyday life and your running.
The second type of carbohydrate is the complex carbohydrate. Complex carbohydrates, unlike the simple sugars, are composed of several glucose molecules linked together. As a result of their more complex structure, they are absorbed more slowly into the bloodstream, providing a more favorable slow and steady supply of energy, thus avoiding the pitfalls of the insulin response.
Since complex carbohydrates maintain a more consistent blood sugar level than do simple carbohydrates, experts recommend that the majority of the calories obtained from carbohydrates be in the form of the complex carbohydrates. Examples of foods that are high in complex carbohydrates include cereals, pasta, breads, rice, potatoes, and vegetables.
With that said, rating carbohydrates purely as “simple and complex” may be too limiting as there is a continuum of insulin responses to varying carbohydrates. For example, there are some complex carbohydrates that elicit a greater insulin response than some simple carbohydrates. To get around this, the Glycemic Index was created. Foods with a high glycemic index cause a greater insulin response than those with a low glycemic index. Your diet will contain both but you may want to shift your eating habits to include more high glycemic index foods when you want a greater insulin response (immediately after a workout for example) or more low glycemic index foods when you want a minimal insulin response (throughout the day). Google "Glycemic Index database" for a listing of Glycemic Index values for thousands of foods.
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