within seconds in the mouth, and that glucose gets into the blood stream quickly. Fructose Slower
Not all sugars travel as quickly into the blood stream. Glucose
makes its way into the bloodstream five times as fast as fructose.
Some studies indicate that glucose can provide energy more
quickly to exercising athletes, but that fructose can provide more sustained energy.
More athletes report difficulty digesting fructose during exercise
than glucose or sucrose. Fats Slowest
Fat, and to a lesser extent protein, slows digestion when
compared with carbohydrate.
This can be an advantage. Fats may result in a slow release of
calories into the blood stream. The ni
ght before an event, a meal with
carbohydrate, fat, and protein will ta
ke longer to digest than one of
carbohydrate alone. Some studies indicate that morning liver glycogen levels may be high
er with this strategy.
This can be a disadvantage. A fatty meal before competition
slows digestion and is more likely to result in cramping and indigestion than one emphasizing carbohydrate. Solids and Hard Work
As we have seen, the digestive tract uses muscles to propel food.
As all muscles, digestive muscles need blood to work.
If you are working hard, your leg muscles need your blood. If it
is hot, lots of blood goes to skin to help cooling. If you are dehydrated, you have less blood volume.
These competing demands mean that during exercise there may
be little blood available to keep intestinal muscles working. The gastrointestinal tract may shut down. You may get abdominal
cramps. If you eat or drink, the food or fluids may just stay in your stomach, giving you bloating. Race Nerves
Anxiety causes the nerve regulators of the gastrointestinal tract
to shut down the digestive function
of the gastrointestinal tact. So
pre-race jitters means you may have
trouble eating and digesting
your food, even if you are sitting down quietly at the table, not exercising.
Nutrition for Sports, Essentials of 42
