The body re-forms a complex carbohydrate for energy storage
called glycogen. Glycogen is the critical fuel for performance in the high aerobic and anaerobic threshold range, and is stored primarily within muscle cells and the liver. Wh
en one exercises for a couple of
hours at high intensity, it is easy to use up these stores.
Since complex carbohydrate is associated with other nutrients
and are critical for glycogen replacement, they form the cornerstone of meal planning.
Maltodextrins
or
glucose polymers
are medium-length chained
carbohydrates, partially broken down from naturally occurring complex carbohydrate. They are often found in energy bars and gels. The contention that they provide a more constant source of energy than simple sugar, one that is easier
to digest than naturally occurring
complex carbohydrate, is only partially true. The discussion of the glycemic index below, explains why.
Fiber
includes indigestible complex carbohydrate. Fiber plays a
role in overall health but has little bearing on athletic performance.
Read about fiber beginning in the free supplement to this book
available at: http://roadbikerider.com/nutritionforsportssupplement.htm
.
Glycemic Index
It used to be thought that simple sugars entered the bloodstream
rapidly but that their effects on energy production were short-lived. It used to be thought that complex sugars provided a steadier release of food energy.
Studies have shown that the rate of release of sugar into the
bloodstream, or glycemic effect, is related to factors other than whether sugars are simple or comp
lex. The rate of digestion of
sugars has more to do with cooking, ripening, and the presence of fiber, fats, and proteins associated with the sugar than it does with the presence of simple sugars. For example, a well-baked potato
releases sugar into the bloodstream almost as rapidly as glucose. The release of simple sugars in whole milk is delayed by the presence of fat. Bananas release sugar more ra
pidly when ripe. Simple sugars
consumed as part of a meal raise blood sugar more slowly than when consumed by themselves.
Pure glucose is assigned a glycemic
index of 100. The rate of
release of sugar into the bloodstream caused by other substances is compared with the release rate of pure glucose.
Sugars that have a glycemic index greater than 80 are considered
to be released quickly. Sugars that have a glycemic index between 40 and 80 are considered to be released moderately. Sugars with a glycemic index below 40 are released slowly.
Sugars that release quickly and help to spare or replace burned
glycogen may be suitable during or after exercise. Sugars that release moderately slowly may be more suitable several hours before or after exercise.
Food
Index
Food
Index
Food
Index
Glucose
100
Bananas
60
Ice
cream
36
Potato, baked
98
Sucrose
60
Milk, whole
34
Carrots, cooked
92
Pasta
50
Milk, fat free
32
Honey
87
Potato chips
50
Beans, kidney
30
Cornflakes
83
Oatmeal
50
Lentils
30
Rice
72
Orange juice
50
Fructose
20
Bread
70
Oranges
43
Carrots, raw
16
Candy bars
65
Beans, baked
40
Beans, soy
15
Raisins
65
Apples
40
Peanuts
10
Table 4. Glycemic index of selected foods.
Nutrition for Sports, Essentials of 46