Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School (3 page)

That turned out to be a good line of questioning. A growing body of work now suggests that physical activity can powerfully affect the course of both diseases. We think it’s because exercise regulates the release of the three neurotransmitters most commonly associated with the maintenance of mental health: serotonin, dopamine, and norepinephrine. Although exercise cannot substitute for psychiatric treatment, the role of exercise on mood is so pronounced that many psychiatrists have begun adding a regimen of physical activity to the normal course of therapy. But in one experiment with depressed individuals, rigorous exercise was actually substituted for antidepressant medication. Even when compared against medicated controls, the treatment outcomes were astonishingly successful. For both depression and anxiety, exercise is beneficial immediately and over the long term. It is equally effective for men and women, and the longer the program is deployed, the greater the effect becomes. It is especially helpful for severe cases and for older people.

Most of the data we have been discussing concern elderly populations. Which leads to the question:

6) Are the cognitive blessings of exercise only for the elderly?

As you ratchet down the age chart, the effects of exercise on cognition become less clear. The biggest reason for this is that so few studies have been done. Only recently has the grumpy scientific eye begun to cast its gaze on younger populations. One of the best efforts enrolled more than 10,000 British civil servants between the ages of 35 and 55, examining exercise habits and grading them as low, medium, or high. Those with low levels of physical activity were more likely to have poor cognitive performance. Fluid intelligence, the type that requires improvisatory problem-solving skills, was particularly hurt by a sedentary lifestyle. Studies done in other countries have confirmed the finding.

If only a small number of studies have been done in middle-age populations, the number of studies saying anything about exercise and children is downright microscopic. Though much more work needs to be done, the data point in a familiar direction, though perhaps for different reasons.

To talk about some of these differences, I would like to introduce you to Dr. Antronette Yancey. At 6 foot 2, Yancey is a towering, beautiful presence, a former professional model, now a physician-scientist with a deep love for children and a broad smile to buttress the attitude. She is a killer basketball player, a published poet, and one of the few professional scientists who also makes performance art. With this constellation of talents, she is a natural to study the effects of physical activity on developing minds. And she has found what everybody else has found: Exercise improves children. Physically fit children identify visual stimuli much faster than sedentary ones. They appear to concentrate better. Brain-activation studies show that children and adolescents who are fit allocate more cognitive resources to a task and do so for longer periods of time.

“Kids pay better attention to their subjects when they’ve been active,” Yancey says. “Kids are less likely to be disruptive in terms of their classroom behavior when they’re active. Kids feel better about themselves, have higher self-esteem, less depression, less anxiety. All of those things can impair academic performance and attentiveness.”

Of course, there are many ingredients to the recipe of academic performance. Finding out which components are the most important—especially if you want improvement—is difficult enough. Finding out whether exercise is one of those choice ingredients is even tougher. But these preliminary findings show that we have every reason to be optimistic about the long-term outcomes.

an exercise in road-building

Why exercise works so well in the brain, at a molecular level, can be explained by competitive food eaters—or, less charitably, professional pigs. There is an international association representing people who time themselves on how much they can eat at a given event. The association is called the International Federation of Competitive Eating, and its crest proudly displays the slogan (I am not making this up)
In Voro Veritas
—literally, “In Gorging, Truth.”

Like any sporting organization, competitive food eaters have their heroes. The reigning gluttony god is Takeru “Tsunami” Kobayashi. He is the recipient of many eating awards, including the vegetarian dumpling competition (83 dumplings downed in 8 minutes), the roasted pork bun competition (100 in 12 minutes), and the hamburger competition (97 in 8 minutes). Kobayashi also is a world champion hot-dog eater. One of his few losses was to a 1,089-pound Kodiak bear. In a 2003 Fox televised special called
Man vs. Beast,
the mighty Kobayashi consumed only 31 bunless dogs compared with the ursine’s 50, all in about 2½ minutes. Kobayashi lost his hot-dog crown in 2007 to Joey Chestnut, who ate 66 hot dogs in 12 minutes (the Tsunami could manage only 63).

But my point isn’t about speed. It’s about what happens to all of those hot dogs after they slide down the Tsunami’s throat. As with any of us, his body uses its teeth and acid and wormy intestines to tear the food apart and, if need be, reconfigure it.

This is done for more or less a single reason: to turn foodstuffs into glucose, a type of sugar that is one of the body’s favorite energy resources. Glucose and other metabolic products are absorbed into the bloodstream via the small intestines. The nutrients travel to all parts of the body, where they are deposited into cells, which make up the body’s various tissues. The cells seize the sweet stuff like sharks in a feeding frenzy. Cellular chemicals greedily tear apart the molecular structure of glucose to extract its sugary energy. This energy extraction is so violent that atoms are literally ripped asunder in the process.

As in any manufacturing process, such fierce activity generates a fair amount of toxic waste. In the case of food, this waste consists of a nasty pile of excess electrons shredded from the atoms in the glucose molecules. Left alone, these electrons slam into other molecules within the cell, transforming them into some of the most toxic substances known to humankind. They are called free radicals. If not quickly corralled, they will wreck havoc on the innards of a cell and, cumulatively, on the rest of the body. These electrons are fully capable, for example, of causing mutations in your very DNA.

The reason you don’t die of electron overdose is that the atmosphere is full of breathable oxygen. The main function of oxygen is to act like an efficient electron-absorbing sponge. At the same time the blood is delivering foodstuffs to your tissues, it is also carrying these oxygen sponges. Any excess electrons are absorbed by the oxygen and, after a bit of molecular alchemy, are transformed into equally hazardous—but now fully transportable—carbon dioxide. The blood is carried back to your lungs, where the carbon dioxide leaves the blood and you breathe it out. So, whether you are a competitive eater or a typical one, the oxygen-rich air you inhale keeps the food you eat from killing you.

Getting food into tissues and getting toxic electrons out obviously are matters of access. That’s why blood has to be everywhere inside you. Serving as both wait staff and haz-mat team, any tissue without enough blood supply is going to starve to death—your brain included. That’s important because the brain’s appetite for energy is enormous. The brain represents only about 2 percent of most people’s body weight, yet it accounts for about 20 percent of the body’s total energy usage—about 10 times more than would be expected. When the brain is fully working, it uses more energy per unit of tissue weight than a fully exercising quadricep. In fact, the human brain cannot simultaneously activate more than 2 percent of its neurons at any one time. More than this, and the glucose supply becomes so quickly exhausted that you will faint.

If it sounds to you like the brain needs a lot of glucose—and generates a lot of toxic waste—you are right on the money. This means the brain also needs lots of oxygen-soaked blood. How much food and waste can the brain generate in just a few minutes? Consider the following statistics. The three requirements for human life are food, drink, and fresh air. But their effects on survival have very different timelines. You can live for 30 days or so without food, and you can go for a week or so without drinking water. Your brain, however, is so active that it cannot go without oxygen for more than 5 minutes without risking serious and permanent damage. Toxic electrons over-accumulate because the blood can’t deliver enough oxygen sponges. Even in a healthy brain, the blood’s delivery system can be improved. That’s where exercise comes in. It reminds me of a seemingly mundane little insight that literally changed the history of the world.

The man with the insight was named John Loudon McAdam. McAdam, a Scottish engineer living in England in the early 1800s, noticed the difficulty people had trying to move goods and supplies over hole-filled, often muddy, frequently impassable dirt roads. He got the splendid idea of raising the level of the road using layers of rock and gravel. This immediately made the roads more stable, less muddy, and less flood-prone. As county after county adopted his process, now called macadamization, an astonishing after-effect occurred. People instantly got more dependable access to one another’s goods and services. Offshoots from the main roads sprang up, and pretty soon entire countrysides had access to far-flung points using stable arteries of transportation. Trade grew. People got richer. By changing the way things moved, McAdam changed the way we lived. What does this have to do with exercise? McAdam’s central notion wasn’t to improve goods and services, but to improve
access
to goods and services. You can do the same for your brain by increasing the roads in your body, namely your blood vessels, through exercise. Exercise does not provide the oxygen and the food. It provides your body greater
access
to the oxygen and the food. How this works is easy to understand.

When you exercise, you increase blood flow across the tissues of your body. This is because exercise stimulates the blood vessels to create a powerful, flow-regulating molecule called nitric oxide. As the flow improves, the body makes new blood vessels, which penetrate deeper and deeper into the tissues of the body. This allows more access to the bloodstream’s goods and services, which include food distribution and waste disposal. The more you exercise, the more tissues you can feed and the more toxic waste you can remove. This happens all over the body. That’s why exercise improves the performance of most human functions. You stabilize existing transportation structures and add new ones, just like McAdam’s roads. All of a sudden, you are becoming healthier.

The same happens in the human brain. Imaging studies have shown that exercise literally increases blood volume in a region of the brain called the dentate gyrus. That’s a big deal. The dentate gyrus is a vital constituent of the hippocampus, a region deeply involved in memory formation. This blood-flow increase, which may be the result of new capillaries, allows more brain cells greater access to the blood’s food and haz-mat teams.

Another brain-specific effect of exercise recently has become clear, one that isn’t reminiscent of roads so much as of fertilizer. At the molecular level, early studies indicate that exercise also stimulates one of the brain’s most powerful growth factors, BDNF. That stands for Brain Derived Neurotrophic Factor, and it aids in the development of healthy tissue. BDNF exerts a fertilizer-like growth effect on certain neurons in the brain. The protein keeps existing neurons young and healthy, rendering them much more willing to connect with one another. It also encourages neurogenesis, the formation of new cells in the brain. The cells most sensitive to this are in the hippocampus, inside the very regions deeply involved in human cognition. Exercise increases the level of usable BDNF inside those cells. The more you exercise, the more fertilizer you create—at least, if you are a laboratory animal. There are now suggestions that the same mechanism also occurs in humans.

we can make a comeback

All of the evidence points in one direction: Physical activity is cognitive candy. We can make a species-wide athletic comeback. All we have to do is move. When people think of great comebacks, athletes such as Lance Armstrong or Paul Hamm usually come to mind. One of the greatest comebacks of all time, however, occurred before both of these athletes were born. It happened in 1949 to the legendary golfer Ben Hogan.

Prickly to the point of being obnoxious (he once quipped of a competitor, “If we could have just screwed another head on his shoulders, he would have been the greatest golfer who ever lived”), Hogan’s gruff demeanor underscored a fierce determination. He won the PGA championship in 1946 and in 1948, the year in which he was also named PGA Player of the Year. That all ended abruptly. On a foggy night in the Texas winter of 1949, Hogan and his wife were hit head-on by a bus. Hogan fractured every bone that could matter to a golfer: collar bone, pelvis, ankle, rib. He was left with life-threatening blood clots. The doctors said he might never walk again, let alone play golf. Hogan ignored their prognostications. A year after the accident, he climbed back onto the green and won the U.S. Open. Three years later, he played one of the most successful single seasons in professional golf. He won five of the six tournaments he entered, including the first three major championships of the year (a feat now known as the Hogan Slam). Reflecting on one of the greatest comebacks in sports history, he said in his typically spicy manner, “People have always been telling me what I can’t do.” He retired in 1971.

When I reflect on the effects of exercise on cognition and the things we might try to recapture its benefits, I am reminded of such comebacks. Civilization, while giving us such seemingly forward advances as modern medicine and spatulas, also has had a nasty side effect. It gave us more opportunities to sit on our butts. Whether learning or working, we gradually quit exercising the way our ancestors did. The result is like a traffic wreck.