by Adrian Raine
The type of malnutrition the kids had did matter a bit, though. Iron deficiency was especially important. This ties in with findings from experimental studies on animals showing that iron is involved in DNA synthesis, neurotransmitter production and functioning,11 and white-matter formation in the brain.12 If iron benefits the brain, low iron should be a problem. And it is. Experimental studies that have supplemented children’s diets with iron show improved cognitive functioning.13 My angular stomatitis, which reflected a vitamin B2 deficiency, would also play a helping hand in poor cognition, because vitamin B2 enhances the hematological response to iron.14 Consequently, riboflavin deficiency would reduce iron and further negatively affect cognition. Eat your vitamin-fortified cardboard cornflakes.
It really does seem that poor nutrition, right across the board—across ages and types of problem behaviors—raises the odds of behavior problems in the growing child. But we get back again to a central, fundamental question. What is the mechanism of action, the way in which nutrition—or rather the lack of it—translates itself into aggressive and antisocial behavior? Back to basics. Back to the brain, and back to cognitive functioning.
Figure 7.2 Dose-response relationship between signs of malnutrition at age three and behavior problems at age seventeen
Jianghong Liu found that the children with poor nutrition at age three also had lower IQs at that age and eight years later at age eleven. She again found a dose-response relationship, with increasing levels of malnutrition resulting in decreasing scores on IQ. If a child had three indicators of malnutrition, her IQ dropped seventeen points. It’s a significant tumble: imagine being average in your class and dropping to the bottom 11 percent—not because of who you are, but because of what you don’t eat. It did not matter what type of cognitive ability we looked at, malnutrition had an influence on verbal IQ as well as spatial (nonverbal) IQ.
In Mauritius, as in my day at primary school, they take national examinations at age eleven to decide what type of secondary school they will go to. The exams are in English, French, mathematics, and environmental studies. It really decides the rest of these children’s lives. We looked at their performance on these standardized national examinations, and again we found that poor nutrition drives down academic scores in a dose-response fashion. The same thing with neuropsychological test functioning at age eleven, and the same thing with reading ability. Poor nutrition sinks school performance and neurocognitive functioning. And yes, we know that poverty and parental education is linked to both IQ and poor nutrition, but controlling for multiple social adversity indicators like these did not alter the relationship. We could not escape the fact that nutrition is in its own right absolutely critical for kids to do well in all realms of intellectual life, and has real-life consequences in determining what level of secondary education the kids end up getting.
From nutrition to cognitive functioning and back to behavior problems. We are on our way to a part-answer to the core question of “What is the mechanism of action?” Does poor nutrition make a dent in cognitive functioning? And do dull wits turn kids to vandalism and antisocial activities? It seems that they do. Liu statistically controlled for the fact that kids with poor nutrition have lower IQ.15 This technique makes the good and poor nutrition groups equal on intelligence. When that is done, the group difference in antisocial behavior disappears. This vanishing trick identifies poor cognition as a likely mechanism. Poor nutrition leads to low IQ, and this lowering of cognitive ability leads to antisocial behavior.
And it makes sense. You can imagine how low IQ can lead to school failure. You likely did well in school, but imagine what it’s like to instead go in every day and get stuck on your reading, get your mind numbed with numbers that don’t add up, while all the time most other kids seem to be doing just fine. Day in, day out, you’re a failure. A failure for weeks, for months, for years.
It’s easy to see how this can result in low self-esteem and a loss of hope. No wonder such kids try to bail out and kick back against the institutional system once they gain the muscle to rebel. Note here that just because poor nutrition acts negatively on the brain to predispose someone to aggression, we are not saying no to social factors altogether. Indeed, poor nutrition is very much an environmental factor. We see here that a negative environment—not getting enough of the right food—results in poor brain and cognitive functioning, which leads some kids down the primrose path to crime and violence. And as we are about to see, it’s something of a slippery slope.
OMEGA-3 AND VIOLENCE: A FISHY TALE
Strange stories abound when it comes to trying to explain violence and other devious behavior. Perhaps one of the strangest circulating at the moment is that it’s all to do with how much fish we eat. This may sound odd, but if we take a close look at the data, what your grandma always told you may be literally true—that fish food is brain food. And if something affects the brain, it’s up for grabs as a causal agent in crime.
We’ll begin with a topic in criminology that does not receive as much attention as it should. Why do countries around the world differ so much in violence, and what’s the cause of these differences? There are plenty of ideas, old and new. Differences in unemployment rates do not seem to explain international differences in homicide and, perhaps surprisingly, neither does urbanization.16 A lot of emphasis has been placed on social processes and for good reason, as the correlational data supports it. As we might expect, gross domestic product (GDP) is a strong correlate—the lower the GDP, the higher the violence: a correlation of .68. It really makes sense if we think of poverty as a cause of crime, because a higher GDP goes along with political development, increased democracy, and better education of the people.
A different social mechanism—income inequality—endorses this social perspective. As measured by the Gini index, the higher the income inequality, the higher the homicide rate—a correlation of .57. So the more a country is divided into the haves and the have-nots, the higher the homicide rate. Denmark, Norway, Sweden, and Japan all have relative income equality and low homicide, while countries like Colombia, Botswana, and South Africa have high inequality and high homicide, with the United States in between on both counts.
Interestingly, psychological beliefs also play a role. Some people prefer money, while others prefer love. What would your own pick be? We all differ to some degree, and just like individuals, countries as a whole differ from each other in the relative value they place on love, on the one hand, versus social status, good financial prospects, power, and status on the other. In countries where people believe love is more important than money, there is less violence. Perhaps the Beatles were not far off the mark—all you need is love.
But we need to eat as well as make love. And this is the fishy part. Countries differ an enormous amount in how much fish they eat, just as they differ in their homicide rates. Joe Hibbeln, a leading fish-oil expert working at the National Institute on Alcohol Abuse and Alcoholism in the United States put yearly homicide rates and fish consumption together. He found that they were negatively related—at a correlation level of -.63.17 Take a look at Figure 7.3. It does look as if something may be going on here. Take Japan. They have very low yearly homicide rates—only one homicide per 100,000 people—and they eat well over their own body weight in fish every year. Then you look at eastern European countries like Bulgaria. They eat a measly four pounds of fish a year and rack up homicide rates ten times that of Japan. If you pick out the East Asian countries, they almost follow a straight line, with China at 4.3 homicides/100,000; Singapore at 3.8; South Korea at 3.0; and Japan at 1.2. The greater the fish consumption, the lower the homicide rate.
Figure 7.3 Relationship between seafood consumption and homicide rates across the world
I showed Joe Hibbeln’s provocative data in a talk I gave to the Criminology Department at the University of Pennsylvania in 2005 when I was being interviewed for a job, and one provocative question posed was, “Wait a bit, where’s America here?” Th
e United States was not on the graph of twenty-six countries. My colleagues-to-be didn’t exactly smell a rat, but felt it was a bit of a slippery story. So they went and looked up the data for the United States for the year in question, and what did they find? Fish consumption right in between the two least-fish-consuming countries, Hungary and Bulgaria, and with homicide rates way up at 9 per 100,000, right next door to the eastern European countries. The correlation of -.63 was large and just as strong as that between GDP and homicide rates.
Explaining differences in violence across countries in the world is one thing, but such explanations may or may not apply to variations in offending within a country. Yet even within countries there is evidence that variation in fish consumption is related to antisocial behavior. In a very large sample—11,875 pregnant women from Bristol, England—women who ate more fish during pregnancy had offspring who showed significantly higher levels of prosocial behavior at age seven.18 Put another way, the offspring of mothers who did not eat much fish during pregnancy had more antisocial behavior.
In the United States, a study of 3,581 people from Chicago, Minneapolis, and Birmingham, Alabama, showed that those who hardly ever ate fish had higher levels of hostility than those eating fish at least once a week.19 There are also more behavior problems and temper tantrums in boys with lower total fatty-acid concentrations as measured from blood.20 The same is true of aggressive cocaine addicts.21 Even dogs with low levels of omega-3 have been shown to be more aggressive.22 Giving your dog omega-3 may do more than give it a sleek, shiny coat.
Let’s just suppose for a minute that this is a causal relationship, that bolting down boatloads of sushi and salmon somehow stops you from blowing your fuse. How on earth could this be possible from a scientific standpoint?
There is a reasonable answer based on experimental studies that manipulate the amount of omega-3 that rats have in their diet.23 Recall from previous chapters that violent offenders have brain structural and functional impairments as well as neurochemical deficiencies. Fish is inevitably rich in fish oil. Fish oil, in turn, is rich in omega-3—a polyunsaturated long-chain fatty acid. Omega-3 has two important components—DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). What does DHA do? It is known to play a key role in neuronal structure and function. Making up 6 percent of the dry cerebral cortex, it influences the functioning of the blood-brain barrier that regulates what gets into your brain from your bloodstream. It enhances synaptic functioning, facilitating communication between brain cells. It makes up 30 percent of the membrane of your brain cell and regulates the activity of membrane enzymes. It protects the neuron from cell death. It increases the size of the cell.
DHA also stimulates neurite outgrowth. There is more intricate dendritic branching in the neurons of animals fed a diet rich in omega-3 compared with those fed a normal diet. Dendrites of the cell receive signals from other brain cells, so this dendritic branching translates to more connectedness between cells. The axon that transmits the electrical signal to other cells is longer and has a better sheath to conduct the electrical impulse. DHA regulates serotonin and dopamine neurotransmitters, and we saw in chapter 2 that offenders have abnormalities in those neurotransmitters. We also know that DHA is involved in regulating gene expression,24 so in theory it can help turn on genes that protect against violence—or turn off genes that increase the probability of violence.
We also saw earlier that cognitive functioning is impaired in offenders. Omega-3 supplementation has been shown to improve learning and memory in animals,25 and also improves learning in children.26 So it’s not just that omega-3 in theory improves the brain. In practice, it makes a difference in terms of cognitive functioning—and cognitive functioning is critical for performance in school and success in life.
Omega-3 enhances both brain structure and function. We saw in earlier chapters that brain structure and function is impaired in offenders. So it’s perhaps not all that surprising that we find associations between the amount of fish consumed and the perpetration of violence.
You might still find this all a bit too much to believe. Surely it can’t be that simple? And correlation is not necessarily causation, right? You’re correct on both counts. But what we will see in a later chapter on treatment is that there is mounting evidence from randomized controlled trials that omega-3 is effective in reducing antisocial behavior—and such trials are as good as it gets in establishing causality and demonstrating a true and meaningful relationship.
But you’re likely still not convinced, are you? What use are these malnutrition studies to the United States, or other prosperous nations? Look around, everyone seems pretty healthy and there’s plenty to eat. These results must be a problem only in developing countries, like Mauritius.
And you’ve got a reasonable point here. Visitors to the United States cannot help but be struck by the abundance of food and the big portions that are served up in basic restaurants. And the desserts are veritable mountains of yumminess. You take a look around you and, well, people do look kinda big in America. Rates of obesity are 30.6 percent for the United States and 23.0 percent for the United Kingdom, compared with 12.9 percent for Germany, 10.0 percent for the Netherlands, and 3.2 percent for both South Korea and Japan.27 There’s certainly no lack of sustenance over here in the United States, so what’s the deal with all the violence?
There are three complementary perspectives to this issue. First, if you meet or see pictures of adult murderers, it’s true that they certainly don’t look malnourished. But this belies the fact that as children some of them, like the killers Henry Lee Lucas and Donta Page, were surviving by rummaging around in garbage cans. Page was an unfed, malnourished, scrawny little boy when he was growing up in the ghettos around Washington, D.C. But when as an adult he raped and killed Peyton Tuthill he weighed in at over 300 pounds. The outer appearances of adult offenders can be very misleading, hiding years of malnutrition at a critical early juncture in life when the brain is rapidly developing.
Second, there are two types of nutrients—macronutrients and micronutrients. Kids in America are getting plenty of the macronutrients—carbohydrates, fat, and protein.28 But the story is different for the second component—the micronutrients that include vitamins and trace minerals, things like iron and zinc. They are “micro” because the amounts we need every day are really small, in the order of micrograms or milligrams. Yet they are critical for the growth and maintenance of body and brain functions. At the level of micronutrients, the World Health Organization argues that up to one half of all the children in the world have iron or zinc deficiency.29 That’s a staggering fact.
Third, we’ve also got to factor in that there is a wide range in the “bioavailability” of nutrients—the ability of the nutrient in question to get into your bloodstream and act on your brain. Bioavailability is influenced both by a host of genetic factors that determine how well nutrients are absorbed from the gastrointestinal tract, and also by environmental factors such as food inhibitors and enhancers. So, essentially, you can have two people with the same intake of micronutrients, but they may differ radically in terms of the degree to which those micronutrients get into their bloodstreams and act on their brains.
Once again, outside appearances and how well-fed a person appears to be can be very deceiving. Big is not better when it comes to body size and nutrition. Genes and environment, the two big gladiator arenas in which we have been seeing violence played out, can also starve the brain of critical nutrients. Given their potential importance, let’s take a brief look at these micronutrients and the roles they may play in violence.
THE MIGHTY MICRONUTRIENTS
What are micronutrients? They include vitamins as well as important trace minerals like iron and zinc. If as a kid you had acne or if you had white spots on your fingernails, as I did, you can suspect zinc deficiency.
Deprive mice of zinc and their aggression increases threefold.30 Even before birth, zinc deprivation during pregnancy in rats increases
their offspring’s aggression.31 Children and adults in the United States with assaultive and aggressive behavior have abnormally low levels of zinc relative to copper.32 A Turkish study similarly found that violent schizophrenics had lower zinc and copper ratios than nonviolent schizophrenics.33
Iron is another important micronutrient. Several studies have found aggressive and conduct-disordered children to be zinc-deficient.34 One study found iron deficiency in a third of juvenile delinquents.35 Preschoolers with low iron also show a reduction in positive emotions.36 This is significant because a lack of positive emotion characterizes conduct-disordered children.37
Let’s link back to the brain again to understand why these micronutrient deficiencies can predispose someone to violence. Micronutrients like iron and zinc are critical for the production of neurotransmitters and are important for brain and cognitive development. If you reduce dietary levels of zinc and protein in rats during pregnancy, then their offspring show impaired brain development.38 Adult animals fed a zinc-deficient diet show “passive avoidance learning deficits.”39 This is an inability to learn to inhibit a response that leads to punishment, a cognitive deficit repeatedly found in offenders who have difficulty learning from their mistakes.40
We can also link micronutrients to specific brain structures involved in violence. The amygdala and hippocampus, which are impaired in offenders, are packed with zinc-containing neurons. Zinc deficiency in humans during pregnancy can in turn impair DNA, RNA, and protein synthesis during brain development—the building blocks of brain chemistry—and may result in very early brain abnormalities.41 Zinc also plays a role in building up fatty acids, which, as we have seen, are critical for brain structure and function.42 The availability of iron in the brain, like zinc, has been shown to affect neurotransmitter production and function.