by Adrian Raine
What results in iron and zinc deficiency? It could be a lack of foods like fish, beans, and vegetables. Bear in mind that micronutrients play an important role in fetal brain development, and up to 30 percent of pregnant mothers with low socioeconomic status are believed to be iron-deficient. Smoking during pregnancy also impairs the transportation of zinc from the mother to her fetus,43 depriving the fetal brain of a key nutrient. We have already seen that smoking during pregnancy predisposes a woman’s offspring to adult violence.
Amino acids are also important because they are what proteins are made out of. Eight of our twenty-two amino acids are essential because our bodies cannot produce them. Animals fed diets reduced in one of these—tryptophan—become aggressive, while high-tryptophan food reduces their aggressive behavior.44 When tryptophan is experimentally reduced in men and women,45 they respond more aggressively when provoked.46 Reversing that scenario, when tryptophan is enhanced, aggressive behavior is reduced.47
Low tryptophan likely increases aggression because it impairs the brain’s ability to inhibit responses that we should not make. Brain-imaging research has shown that reducing tryptophan reduces functioning in the orbital and inferior regions of the right prefrontal cortex when subjects try to refrain from making a response to a stimulus.48 We saw earlier that this underneath part of the prefrontal cortex is functionally and structurally impaired in offenders. Because serotonin is synthesized from tryptophan, the amino acid likely predisposes someone to reactive aggression by lowering brain serotonin, the neurotransmitter we saw in chapter 2 to be depleted in impulsive violent offenders.
Where does tryptophan come from? Foods like spinach, fish, and turkey. We see that omega-3 from fish could have a calming effect on aggression. In addition to fish, you might also tell your kids to eat their spinach—even if Popeye is not exactly the best role model for nonaggressive behavior.
TWINKIES, MILK, AND SWEETS
Sugar rush. Many of us have experienced it. We eat a ton of high-carbohydrate foods and drinks and then feel an energy rush that can make us feel able to shoot for the stars. Then we can feel a little agitated, get light-headed and on edge, and make a crash landing. That’s what was claimed when Dan White killed the mayor of San Francisco, George Moscone, along with the city supervisor and gay-rights activist Harvey Milk.
Dan White was down in the dumps. Life wasn’t working out too well. Having gone from serving in the Vietnam War to working as a police officer and then as a firefighter, he was familiar with high-risk life adventures. But his latest risky venture, a potato restaurant, wasn’t working well, and he was out of money. He had resigned his position on the San Francisco Board of Supervisors—a position he had gained with strong union support from both firefighters and the police.
He had also fallen out with Harvey Milk, who was supporting the establishment of a juvenile detention center that had been proposed by the Catholic Church and was located in White’s district. Now, while Dan White was a Roman Catholic, he was dead set against having the detention center in his district. He also had a gripe with gays, and Harvey Milk was gay. White had resigned from his political position to focus on his potatoes, but with their failure he went back to Mayor Moscone to regain his position. Moscone was in favor, but Milk was against White’s reappointment.
In a fit of reactive aggression, White took a gun and entered San Francisco City Hall through a window to avoid the metal detectors. He went into Mayor Moscone’s office and begged him to restore his position. Moscone refused, so White shot him dead. He then went into Harvey Milk’s office and shot him dead too.
Enter the Twinkie. At his trial, White’s defense team and their psychiatrists argued that he was suffering from depression and had immersed himself in an orgy of junk foods and drinks packed with refined sugar. Bad diet could influence his mood. White was a white working-class heterosexual all-American Catholic who had fought for his country and once saved a woman and her baby from a fire. The jury was made up of predominantly white working-class people who shared White’s values. Some openly wept when they heard the pressure he was up against in his life. Instead of first-degree murder and the death penalty, he was found guilty of voluntary manslaughter and received a prison sentence of seven years and eight months.
The San Francisco gay community went nuts. Even Acting Mayor Dianne Feinstein proclaimed: “Dan White has gotten away with murder. It’s as simple as that.”49
White’s defense had been buttressed by $10,000 that the police had raised for him. The result was the “White Night Riots.”50 A crowd of 1,500 quickly gathered that night in the predominantly gay Castro District, where Milk had lived. It grew to an ugly 3,000 who descended onto City Hall and tore the place apart.51 Police cars were set on fire. After establishing order at City Hall, police retaliated by going into bars in the Castro area and beating up gays. Sixty-one police officers and over a hundred gays were hospitalized for injuries. Dan White eventually committed suicide.
All this because of a little Twinkie?
Not quite, but near enough. Twinkies themselves—sponge cakes with cream filling—were never actually brought up at Dan White’s trial, and the term “Twinkie Defense” was a phrase invented by the press. But junk food was brought up at the trial. Could it really contribute to diminished rational thought, as the defense argued? The claim certainly caught on rapidly after the trial. As one protestor put it to reporters as he was setting fire to a police car on that White Night, “Make sure you put in the paper that I ate too many Twinkies.”52
White’s behavior may or may not have been influenced by junk food, and even if it did contribute to the homicides, we are hard-pressed to view this as an excuse—either an excuse for Dan White’s outrageous actions or, indeed, an excuse for the reactions of the local community. But if there is a mechanism at play here with respect to aggression, the likely candidate is refined carbohydrates. A number of studies have claimed that dietary changes aimed at reducing sugar consumption reduce institutional antisocial behavior in juvenile offenders. Some of these claims are striking. For example, one early controversial study—a two-year double-blind controlled study of twelve- to eighteen-year-old delinquents—obtained a 48 percent reduction in disciplinary offenses after diets were altered in order to reduce refined carbohydrates.53 Experimental studies in animals have also demonstrated a causal relationship between low blood sugar and aggression in rats.54
Let’s move on to Peru and the Quolla Indians for another course in the recipe for violence. The Quolla have a very high rate of homicide and incessantly feud with each other, and have been called, a bit harshly, “perhaps the meanest and most unlikeable people on earth.”55 One anthropologist who studied them made the keen observation that a significant number of their acts of aggression seemed to be without good cause.56 He also noticed that the Quolla were often hungry and craved sugar. Could it be that their irrational aggression was due to low blood-sugar levels and reactive hypoglycemia? A glucose-tolerance test, which assesses propensity for low blood-sugar levels, confirmed a relationship between low blood sugar and both physical and verbal aggression in the Quolla.57 When you next feel irritable and angry for reasons that are not obviously apparent, you might consider a quick nutritious nibble to restore your sugar levels—but not a Twinkie.
In Finland, Matti Virkkunen, who is a psychiatrist at Helsinki University, has been repeatedly demonstrating in some important studies very significant metabolic abnormalities in violent offenders that fit the low-blood-glucose idea. In a series of early studies, Matti demonstrated that violent offenders were more prone to hypoglycemia. He demonstrated that aggressive psychopaths had increased insulin secretion, which would explain their low blood-sugar levels.58 More recently, Matti found low glucose metabolism and low levels of the hormone glucagon in another group of violent Finns.59 He then found that low glucose and glycogen formation predicted which violent offenders would go on to commit further violence eight years later, with the two measures explaining 27 percent o
f this future recidivism.60
If Matti Virkkunen and others are right, how exactly would the recipe of junk food, hypoglycemia, and low glucose metabolism push a person to violence and aggression? It goes something like this. Diets high in refined carbohydrates can cause extreme fluctuations in blood glucose levels—foods like white bread and white rice. Such foods have the bran, germ, and nutrients stripped from the whole grain, taking away the fiber. Because of the fiber loss, they are rapidly absorbed by the gut, resulting in a large and rapid increase of glucose swishing around in the bloodstream. This in turn triggers an inappropriately large secretion of insulin. Insulin’s job is to soak up the excess glucose and convert it into glycogen so that surplus energy can be stored for future use. But too much insulin release results in too much of the available glucose being taken out of circulation. This is bad news for the brain, which requires at least 80 milligrams of glucose a minute to function efficiently. Drop below that mark and you progressively observe symptoms of nervousness and irritability. That combo of increased irritability combined with feeling on edge could be the first step in the development of a full-blown aggressive outburst. It’s not too surprising, therefore, that when glucose levels of subjects are experimentally lowered in the laboratory, people report feeling more angry even though there is no provocative stimulus.61
But what’s really shocking is a recent study by Stephanie van Goozen and her colleagues at Cardiff University in Wales that was conducted on a sample of 17,415 British babies born in 1970.62 When they were ten years old, the children were asked how often they ate sweets. Van Goozen showed that the kids who ate sweets every day were three times more likely to become violent by age thirty-four. They controlled for many factors, and the results remained significant.
If this relationship is causal, what’s going on? It could be reactive hypoglycemia. The kids who are helping themselves to candy at age ten are also helping themselves to a lifestyle of unhealthy eating habits—high-energy, highly refined carbohydrates that result in too much sugar too quickly. The resulting rebound of very low blood sugar and symptoms of irritability can predispose a kid to giving someone else a good punch in the face in the school playground. Or, as an adult, a broken bar glass in the face. Keep your kids off the candies.
HEAVY METALS MAKE FOR HEAVY HITTERS
If you think sweets are bad for you, they’re nothing compared with other things that can get inside you, mess up your brain, and make you flex your muscles. I’ll suggest here that heavy metals can form some of the ingredients in the concoction for crime causation. Let’s take a look at a few of the key ingredients.
Lethal Lead
We saw in chapters 3 and 5 that the structure and function of the brains of violent offenders—especially the prefrontal cortex—is compromised. We have also hypothesized that these brain impairments produce secondary effects—emotional, cognitive, and behavioral—which in turn shape violence. Lead is a leading candidate as a source of these structural and functional brain impairments.
First and foremost, lead is neurotoxic, meaning that it kills neurons and damages the central nervous system. The neurotoxic effects of lead have been known for millennia, and efforts to reduce it are not recent. They have a connection to my favorite drink in England—cider. Back in the seventeenth and eighteenth centuries there was a common malady known as Devon colic, a neurological condition that particularly afflicted people in the southwest of England. They grow a lot of apples down in Devon and cider was almost a staple drink there back then. It was thought that the acidic apple juice caused the colic. Yet in the late eighteenth century George Baker, a physician, identified the cause as lead contained in the cider presses. Over the next few decades lead was steadily taken out of the presses. A near-miraculous reduction in Devon colic occurred, proving Baker’s hypothesis.
Lead’s neurotoxic effects are documented in brain-imaging studies of workers exposed to the metal in their jobs. One study scanned the brains of 532 adult men who had worked in a lead chemical plant.63 There was a wide range of bone-lead levels in these participants, but an average reading was at the very top of the safety level.64 Workers with relatively high bone-lead levels had smaller volumes of many brain areas even after controlling for multiple confounds like age and education levels. The fact that the frontal cortex was particularly reduced65 is very interesting, given that this brain region is involved in violence. This lead effect was equivalent to five years of premature aging of the brain.
So lead workers have brain volume reductions. What about people in the community like you and me who likely have just low to moderate levels of lead in our blood? This question was addressed in a study of 157 individuals from Cincinnati who had had their blood-lead levels measured twenty-three times from the ages of six months to six and a half years.66 This prospective study again showed that those with high lead levels had low brain volumes. One of the brain regions most affected was the ventrolateral prefrontal cortex, that lower outer region of the front of the brain that is impaired in antisocial and psychopathic individuals. This community sample had an average blood-lead level at age six that was high, but still within the so-called “safe” range as defined by the Centers for Disease Control and Prevention. We can see, then, that those exposed to “safe” levels of lead can suffer from brain impairments. Furthermore, the prospective nature of the study, moving from childhood lead exposure before age six to brain structure at age twenty-three, helps to establish causality.67
These studies give clear documentation of the negative impact of lead on the brain, and, intriguingly, they also document that the brain area most frequently found to be compromised in violent populations—the frontal cortex—is particularly impacted by lead exposure. The next question is whether those with high lead levels are found to be more antisocial.
The landmark study in this area was conducted by Herbert Needleman at the University of Pittsburgh. He found that boys with high lead levels have higher teacher ratings of delinquent and aggressive behavior, and also higher self-reported delinquency scores. It was an impressive and influential study. Similar links have been found in at least six other studies in several different countries.68 Furthermore, experimental exposure to lead during development increases aggressive behavior in hamsters, thus suggesting a causal link.69
Environmental lead exposure, therefore, is a risk factor for antisocial and aggressive behavior in delinquent kids. What about adult crime? And how early in life does this association occur? Answers to these questions were obtained in a methodologically strong study of African-American pregnant women.70 Both prenatal and postnatal blood-lead levels in their offspring dramatically predicted adult crime in the early twenties and also adult violence. For every 5 microgram increase in prenatal blood-lead levels, there was a 40 percent increase in the risk for arrest.71 Given that a 5 microgram increase from birth to age five still keeps you well below the limits of what the Centers for Disease Control and Prevention considers safe, this constitutes substantial risk from just a moderate, “safe” amount of lead exposure.
The last study shows that blood lead very early in life is an important predictor of adult crime. We also know that blood-lead levels are maximal at twenty-one months, when children are most exposed to lead.72 Why is that? You know that toddlers put their fingers in their mouths a lot. And they also get their fingers into every pie they can, including mud pie outside in the garden. Lead lingers well after its release into the environment and stays in the soil for years. Even though gas is now unleaded, the lead residue from the past still lingers in the soil, especially near major roads and freeways.
High blood-lead levels later in childhood can be even more important. One study in Yugoslavia73 recruited pregnant mothers in 1992, just at the time of the large-scale ethnic conflict between the Serbs and the Croats. The mothers came from two towns near lead smelters. Blood-lead levels in their offspring at age three were more strongly related to destructive behavior than the prenatal measures of blood lead. Simila
r findings have been obtained in America, with high blood lead at age seven—but not age two—correlating with high antisocial and aggressive behavior at age seven.74 So lead exposure still matters well after the age of twenty-one months.
Lead research lends itself to an intriguing conceptual point. What has puzzled criminologists is the unpredicted drop since 1993 in violence after a continuous rise, which flew in the face of criminological predictions of further increases. For example, within seven years violent crime in New York had dropped 75 percent. Many sociopolitical explanations were given, but none could account for both the rise and the fall in crime across several decades. Critics of neurocriminology argue that biology cannot, of course, explain differences in violence over time or across regions within a country. Isn’t biology fixed and static? Surely it cannot explain secular trends—shifts in violent crime rates across time.
But it can, and dramatically so. In research papers buried in an obscure environmental journal, Rick Nevin documented a strikingly strong relationship between changes in environmental lead levels from 1941 to 1986, and corresponding changes in violent crime twenty-three years later in the United States.75 So, young children who are most vulnerable to lead absorption go on twenty-three years later to perpetrate adult violence. As lead levels rose throughout the 1950s, 1960s, and 1970s, so too did violence correspondingly rise in the 1970s, 1980s and 1990s. When lead levels fell in the late 1970s and early 1980s, so too did violence fall in the 1990s and the first decade of the twenty-first century. Changes in lead levels explained a full 91 percent of the variance in violent offending—an extremely strong relationship.
Nevin found exactly the same matching of the lead levels and violence curves in Britain, Canada, France, Australia, Finland, Italy, West Germany, and New Zealand.76 There was cross-cultural replication. Furthermore, in states where lead levels dropped more quickly, later violent crime also dropped more quickly.77 Variations in lead levels even correlate with variations in crime rates within cities.78 From international to national to state to city levels, the lead levels and violence curves match up almost exactly.