Do you grab a candy bar when you feel tired? Do you soothe your weary mind with a
doughnut? These quick fixes offer a temporary high that could actually be fueling your fatigue,
sending you on a blood-sugar roller coaster. For example, researchers at Kansas State University
measured mood in 120 college women who drank twelve ounces of water or beverages sweetened
with either aspartame (NutraSweet) or sugar. Within 30 minutes the women who drank the sugarsweetened beverage were the drowsiest. Some people are so sensitive to sugar or caffeine that they
feel tired, irritable, or depressed within an hour of eating even two cookies or drinking one cup of
coffee. Others can tolerate large sugar doses before symptoms develop.
Sugar is a good source of carbohydrate—the energy fuel—so why do sweets bring you down?
For one thing, unlike starch, which slowly releases carbohydrate units called glucose into the blood,
sugar dumps rapidly into the bloodstream, causing a rapid rise in blood sugar. To counteract this
rise, the pancreas quickly releases insulin, which shuttles excess sugar from the blood into the cells.
Consequently blood sugar drops, often to levels lower than before the snack.
Sugar also increases tryptophan levels in the brain and triggers the release of the brain
chemical serotonin, which in turn slow you down. A researcher and a professor of psychology at the
MIT report that people feel sleepier and have “less vigor” for up to three and a half hours after
eating a highly refined carbohydrate snack, as compared to a snack that contains more protein. Finally, people who frequently snack on sweets are likely to consume inadequate amounts of
the energizing nutrients. Researchers in Australia report that the more sugar people consume, the
higher their fat and calorie consumption and the lower their intake of vitamins and minerals.
Consuming sugar as a quick fix for dwindling energy merely results in a temporary high, but in
the long run, it can initiate a vicious energy cycle. 【題組】39. Which of the following items is NOT increased or released after the intake of sugar?
(A) insulin (B) tryptophan (C) serotonin (D) calcium