Study Sees a Sugar-Adrenaline Link in Children
By JANE E. BRODY
Published: March 15, 1995
ALTHOUGH parents commonly complain that their children become wild and inattentive after eating a lot of sweets, most researchers have steadfastly insisted that the effects of sugar on children are negligible, if they exist at all. But now a new study by pediatric researchers at Yale University School of Medicine suggests that the parents' observations may be correct.
The study showed that within hours after normal, healthy children are given a lot of sugar on an empty stomach, their bodies release large amounts of the hormone adrenaline, which causes symptoms like shakiness, anxiety, excitement and concentration problems. The children were more likely to report or exhibit these symptoms, and an examination of their brain waves revealed significant changes in their ability to pay attention.
Adults given comparable sugar doses (adjusted for differences in body size) showed no such effects, said Dr. Susan Boulware, a member of the research team, which was headed by Dr. William V. Tamborlane. Their report was published in the February issue of The Journal of Pediatrics.
Their data "do not indicate that dietary sugar is the cause of hyperactivity problems," the team noted, although this is a popular claim among parents. But Dr. Boulware said in an interview that the effects of sugar on behavior could not be determined from this study because all the children were tested while resting in bed. She said a follow-up study was planned to analyze behavioral effects of sugar in children.
When sugar is consumed along with other nutrients like fat and protein, the rise in blood sugar is greatly blunted, Dr. Boulware said, adding that the main message to be derived from the current findings is that sweet desserts after "mixed meals that include protein, fat, complex carbohydrate and fiber" are preferable to sweet snacks between meals. She also suggested that a snack like peanut butter on a graham cracker or half a cheese sandwich would help children concentrate better and feel more serene than either no snack or a purely sugary snack when they get hungry and their blood sugar levels fall.
She said a follow-up study would examine the effects of sugar eaten with or immediately after a balanced meal.
Previous studies focused mainly on how children's blood sugar levels responded to various amounts of dietary sugar. Normally, when sugar is consumed, blood sugar rises and the body releases the hormone insulin to process the sugar and bring the blood sugar level back to normal. However, when sugar is consumed by itself, insulin can overshoot its mark and, as a result, hours later the blood sugar can drop too low. Then the body releases a second hormone, adrenaline (also called epinephrine) to bring the blood sugar level back to normal. Adrenaline, the fight-or-flight hormone, also induces significant behavioral effects, revving up a person to prepare for immediate action.
In the Yale study, 25 healthy children, from 8 to 16 years old, and 23 young adults consumed the sugar equivalent of two 12-ounce cans of cola. As expected, blood sugar initially rose in both groups and about three hours later began to fall. However, blood sugar levels fell significantly further in the children than in the adults. More important, the children's adrenaline levels rose twice as high as the adults' and remained elevated during the five hours of scientific observation. Not surprisingly, the children also exhibited more symptoms of adrenaline release than did the adults, the researchers reported.
Dr. Boulware explained that adverse effects on the children's cognitive functions were seen at blood sugar levels of 60 to 65 milligrams of glucose per deciliter of blood, whereas in adults such effects are not seen until the blood sugar level drops to 55 or lower. Normal fasting blood sugar levels are about 75 to 80. Thus, the brain of a child appears to be more sensitive than the adult brain to the effect of low blood sugar.