Boost Your Brain (12 page)

A Combined Effect

We’re still working to understand exactly how exercise grows the brain. Increased BDNF no doubt is a major part of the story, especially when it comes to growth in the hippocampus. But there are other reasons exercise grows the brain.

For starters, exercise promotes cardiovascular health, helping the heart pump blood more efficiently to all parts of the body, the brain included. One way it does this is by increasing levels of high-density lipoproteins (HDLs), the “good cholesterol” in the blood, which allows blood to flow more freely. Another, as you’ll recall from the first pages of this book, is via a process called angiogenesis, the creation of new blood vessel branches. Exercise promotes angiogenesis. That means that as you exercise you’re actually adding to the brain’s network of blood vessels, bringing more oxygen to every part of the brain.

In fact, if you look at the network of blood vessels in the brains of exercising adults, as one 2009 research study did, you’ll find it far more extensive than the blood vessel networks that exist in the brains of their sedentary peers.
⁹
For that study, the research team performed magnetic resonance angiography (MRA) on the brains of fourteen healthy elderly participants. Seven of the participants reported a high level of aerobic activity—at least three hours a week over the prior ten years—while the other seven reported exercising less than ninety minutes a week over the prior ten years.

Looking at the results, the study team found that those who had exercised more had healthier-appearing blood vessels and more branchings of their small blood vessels. The difference between the two sets of brains is striking—and the effect might even have been greater than we can see on MRA, since some of the brain’s blood vessels (called capillaries) are so tiny that they can only be measured through a microscope.

A healthy vascular network with dense branches of blood vessels means more nourishment for neurons, helping them to stay vibrant and alive, and better retention of the brain’s highways, allowing different parts of the brain to communicate more efficiently. The newly formed and engorged blood vessels may also account for part of the remarkable growth in the size of the hippocampus with exercise.

In addition, exercise aids the brain in another way: by promoting the creation of new mitochondria, the powerhouses of energy within cells. These new mitochondria are born throughout the body but are put to use in different ways. In muscles, for example, they power the processes needed to add muscle mass, bulking up your biceps when you lift weights or your calves when you run.

In the hippocampus (which I sometimes think of as our “memory muscle”), mitochondria help fuel the growth of new cells, new synapses, and new small blood vessel branchings. The additional energy they provide is critical to rejuvenation and repair elsewhere in the brain, too. I believe mitochondria are the ultimate brain revitalizer—the more we have, the longer we’ll live and the sharper we’ll be in old age.

Running to Alpha

There’s one other factor in how exercise changes the brain: healthy brain activity. Exercise can promote healthy brain wave activity by increasing activity in the healthy alpha range, which is associated with a calm, alert, focused state of mind.

In one study, researchers in Germany and Australia used EEG to measure the baseline brain wave activity of twenty-two recreational runners between the ages of twenty-one and forty-five.
¹⁰
The study participants then ran on a treadmill. When they finished, their brain wave activity was again measured via EEG. What the research team found: in all the study subjects, alpha brain wave activity increased immediately after exercise.

Alpha activity was especially strong in the left frontal lobe—the part of the brain that’s most closely associated with focus, attention, and decision making. That this occurs will be no surprise to anyone who has ever experienced the rush of a “runner’s high.” Part of that feel-good effect is due to the release of endorphins and dopamine, neurotransmitters that promote a sense of well-being. It’s possible that increased levels of these or other feel-good brain-messenger molecules promote alpha activity in the brain. Or that the rush of oxygen-rich blood flooding the brain during exercise is what’s behind that increased alpha activity. Or, more likely, a combination of factors.

I am looking forward to seeing additional solid evidence detailing the link between exercise and healthy brain activity; in the meantime, it’s clear that exercise does indeed help us enter the alpha zone. For proof, all you need to do is consider how
you
feel after vigorous exercise.

Faster? Stronger?

There’s still much research needed to determine how much exercise—and of what type—is most beneficial. For now, however, it’s clear that vigorous aerobic activity offers brain benefits. Walking is better than not walking. But adding intensity—and resistance—may offer a robust advantage.

One recent small study presented at the Canadian Cardiovascular Congress offered evidence that a program of high-intensity interval training, plus resistance training, may help improve cognitive function.
¹¹

For the study, six middle-age men and women participated in a four-month exercise program, which included two days a week of high-intensity interval training (HIIT). The training consisted of thirty minutes of exercise followed by ten minutes of high-intensity interval training, which involved intervals of thirty seconds of sprints and thirty seconds of lower-intensity cycling. Participants also had twice-weekly resistance training sessions.

After four months, the HIIT participants showed a 10 to 25 percent improvement in cognitive processing speed and short-term memory, as well as increased blood flow to their frontal lobes. This may be an indicator that short bursts of intensity promote mitochondrial biogenesis in the brain, just as they do in muscles.

One shortcoming of the study was that it did not include a control group that had only continuous moderate exercise, without HIIT. However, other studies have shown high-intensity exercise significantly increases the number of mitochondria,
¹²
so I favor adding short bursts of HIIT at the end of my own fitness training.

The Stroke Link

You’ll read in
chapter 12
about the devastating effects of a stroke, which is, without question, one of the biggest brain shrinkers. Imagine if we had an intervention that proved highly effective in reducing the risk of stroke. What if it were free? What if it were accessible to almost everyone, at any age?

You’ve guessed where I’m going with this, I’m sure. We do have such an intervention: exercise. Physical activity can go a long way to reducing a variety of vascular risk factors, which in turn reduce the risk of stroke. And it’s not a small effect.

In one study published in 2011, a team of researchers looked at 1,238 stroke-free participants enrolled in the Northern Manhattan Study.
¹³
Participants’ average age was seventy, and all underwent MRIs to check for silent strokes. They were then sorted into quartiles based on their physical activity levels. Compared to those who didn’t exercise, those in the highest quartile exercise group were almost half as likely to show small strokes on their MRIs.

Exercise boosts BDNF, enhances oxygen flow, and promotes healthy brain activity. The more you increase your fitness, the more you will build a bigger “memory muscle” in your hippocampus. For optimal brain growth, I recommend thirty minutes of vigorous aerobic activity, plus fifteen minutes of resistance training, five days a week.

Your Rx

You need to exercise, but don’t head to the gym until you have the “all clear” from your doctor. In the meantime, here’s a preview of the tracks you’ll choose from in chapter 8 as part of your brain fitness program:

Track 1

If you lead a sedentary lifestyle and are currently not exercising at all, this is your track. I want you to exercise, but I don’t expect you to run a marathon (at least not anytime soon). As excited as you are, be sure to start slowly. You don’t want to risk an injury. If you have physical limitations, talk to your doctor about substitutions for walking or jogging.

Week One:
Start by walking for ten minutes at a time, three days a week.

Week Two:
Increase your walking time to fifteen minutes, three days a week.

Week Three:
Increase your walking time to twenty minutes, three days a week. In addition to your scheduled time, find ways to work activity into every day. Take the stairs, park at the far end of the parking lot, walk to lunch, go for a hike instead of going to the movies—do anything you can to replace sedentary moments with activity.

Track 2

If you’re not completely sedentary—for example, if you walk a good bit for work—and exercise occasionally, this is your track.

Week One:
Walk fast or jog for twenty minutes, three days a week. (Don’t count time you walk at work; this must be twenty uninterrupted minutes.)

Week Two:
Increase your walking or jogging time to thirty minutes, four days a week. If you’re walking, try to jog at least some of the time. Increase the amount of time you jog versus walk as the weeks progress.

Week Three:
Increase your walking or jogging time to thirty minutes, five days a week. Gradually increase the intensity of your workouts. Ideally, you want to get to a level of intensity to achieve 60 to 80 percent of your maximum heart rate. If you’d like, you can substitute a stationary bike, swimming, or another aerobic activity, or you can substitute a one-hour game of tennis (or another intense activity) for two of your thirty-minute sessions.

Track 3

If you already exercise twice a week or more, this is your track.

Week One:
Do thirty minutes of uninterrupted aerobic activity, five days a week, plus five extra minutes of weight lifting, push-ups, or another muscle-building activity, three days a week.

Week Two:
Continue with thirty minutes of uninterrupted aerobic activity, five days a week. Bump up your muscle building to ten minutes, three days a week.

Week Three:
Continue with thirty minutes of uninterrupted aerobic activity, five days a week. Bump up your weight lifting to fifteen minutes, five days a week. Increase the intensity of your workouts as needed so that you’re improving your physical fitness. Consider adding high-intensity interval training (HIIT), consisting of five bursts of vigorous exercise during the last fifteen minutes of your exercise routine (five bursts for one minute each, followed by two minutes of less intense activity). You should feel tired after you finish your exercise.

CHAPTER FIVE

Your Recipe for a Bigger Brain

I
F I WERE TO TELL
you that what you eat affects your brain health, you would probably roll your eyes. We’ve all heard—for years!—about brain food. We know we’re supposed to eat blueberries and spinach. We know that they contain antioxidants and will counteract inflammation in our bodies. We know that in some mysterious way this is supposed to help us stay mentally sharp as we age.

What most people
don’t
know is that the food you eat literally reshapes your brain.

Scientists have long had an inkling of this. Way back in 1972 Romanian psychologist and chemist Corneliu E. Giurgea used the term “nootropic” to describe substances that stimulate nerve growth or affect the brain’s neurochemicals or oxygen supply. Since then, a growing body of research has added solid proof to the notion that what we eat affects our brains’ structure and size—and therefore how, and how well, we think.

And while inflammation undeniably has an impact on our long-term brain health, it’s nowhere near the only factor at play. Just as exercise does, brain foods work their magic by boosting BDNF and increasing blood flow to the brain. Some, like green tea, even heighten healthy brain activity.

The end result is a thicker cortex and a larger hippocampus, which together add up to a more fully “funded” brain reserve that serves us both now and in the future.

But growing your brain through diet isn’t just a matter of adding a few key ingredients to your food or popping a few pills. A brain-boosting diet also steers you clear of known brain shrinkers, such as obesity, diabetes, high blood pressure, high cholesterol, metabolic syndrome, and stroke (you’ll read about these in part IV).