Willpower

the bloodstream and is pumped throughout the body. The muscles, not surprisingly, use plenty of glucose, as do the heart and liver. The immune system uses large quantities, but only sporadically. When you’re relatively healthy, your immune system may use only a relatively small amount of glucose. But when your body is fighting off a cold, it may consume gobs of it. That’s why sick people sleep so much: The body uses all the energy it can to fight the disease, and it can’t spare much for exercising, making love, or arguing. It can’t even do much thinking, a process that requires plentiful glucose in the bloodstream. The glucose itself doesn’t enter the brain, but it’s converted into neurotransmitters, which are the chemicals that your brain cells use to send signals. If you ran out of neurotransmitters, you’d stop thinking.
    The link between glucose and self-control appeared in studies of people with hypoglycemia, the tendency to have low blood sugar. Researchers noted that hypoglycemics were more likely than the average person to have trouble concentrating and controlling their negative emotions when provoked. Overall, they tended to be more anxious and less happy than average. Hypoglycemia was also reported to be unusually prevalent among criminals and other violent persons, and some creative defense attorneys brought the low-blood-sugar research into court.
    The issue became notorious during the 1979 trial of Dan White for the assassination of two city officials in San Francisco, Mayor George Moscone and Harvey Milk, a member of the board of supervisors and the most prominent openly gay politician in America. When a psychiatrist testifying for the defense cited White’s consumption of Twinkies and other junk food in the days before the murders, journalists mocked White for trying to excuse himself with a “Twinkie defense.” In fact, White’s chief defense wasn’t based on the argument that the Twinkies turned him murderous by causing his blood-sugar levels to quickly spike and then crash. His attorneys argued that he deserved mercy because he suffered from “diminished capacity” due to severe depression, and they presented his junk-food consumption (along with other changes in habits) as evidence of his depression, not as the cause of it. But when White received a relatively light sentence, the popular wisdom became that the Twinkie defense had worked, and the public was understandably outraged.
    Other defense attorneys actually did argue, with limited success, that their clients’ blood-sugar problems should be taken into account. Whatever the legal or moral merits of that argument, there certainly was scientific data showing a correlation between blood sugar and criminal behavior. One study found below-average glucose levels in 90 percent of the juvenile delinquents recently taken into custody. Other studies reported that people with hypoglycemia were more likely to be convicted of a wide variety of offenses: traffic violations, public profanity, shoplifting, destruction of property, exhibitionism, public masturbation, embezzlement, arson, spouse abuse, and child abuse.
    In one remarkable study, researchers in Finland went into a prison to measure the glucose tolerance of convicts who were about to be released. Then the scientists kept track of which ones went on to commit new crimes. Obviously there are many factors that can influence whether an ex-con goes straight: peer pressure, marriage, employment prospects, drug use. Yet just by looking at the response to the glucose test, the researchers were able to predict with greater than 80 percent accuracy which convicts would go on to commit violent crimes. These men apparently had less self-control because of their impaired glucose tolerance, a condition in which the body has trouble converting food into usable energy. The food gets converted into glucose, but the glucose in the bloodstream doesn’t get absorbed as it circulates. The result is often a surplus of glucose in the bloodstream, which might sound beneficial, but it’s like having plenty of firewood and no matches. The glucose remains there uselessly, rather than being converted into brain and muscle activity. If the excess glucose reaches a sufficiently high level, the condition is labeled diabetes.
    Most diabetics aren’t criminals, obviously. Most keep themselves and their glucose levels under control by monitoring themselves and using insulin when necessary. Like Jim