Secret Life of the Grown-Up Brain (20 page)

10 Food for Thought

And a Few Other Substances, as Well

In 2008, the giant British drug company GlaxoSmithKline announced it would pay $720 million to a small Massachusetts biotechnology company that’s been working for years to prove that we can extend our lives by drinking a lot of red wine.

Specifically, the company had been trying to develop a pill with a high concentration of resveratrol, the ingredient in red wine that some believe may hold a key to keeping our cells, including our brain cells, healthy and nimble.

But Glaxo was not paying for something that’s known to work in actual humans. It paid $720 million to a company whose work so far had shown that resveratrol can extend the life of yeast and, to a certain extent at extremely high doses, rodents.

Is this madness?

Clearly, we want very much for it
not
to be madness. The idea that something as simple as the wine we drink—or the food we eat—can make us think better and live longer is highly seductive. Indeed, it’s hard to think of a topic more steeped in hope—and hype—than the brain and food.

As I write this, I’ve just returned from a Whole Foods supermarket, where a young woman—hired as a kind of modern-day circus barker—was handing out free samples of a new bottled tea. “Try it! You’ll love it!” she nearly shouted to shoppers as they pushed their carts. “It’s got MORE antioxidants than green tea!
More antioxidants for your brain!
”

I took one of her tiny plastic cups of tea and in one gulp drank it down. Was I smarter? Sharper? Was my middle-aged brain better braced with those antioxidants sloshing around?

Hmmm . . . well . . . maybe.

Even those who study all this for a living are confused. While a consensus has emerged over the benefits of exercise and, to a certain degree, education, agreement on what works beyond that falls off a steep cliff.

“The message seems to change every year,” says Mark Moss, the neuroscientist at Boston University, with a sigh.

Part of the problem in talking about food and the brain is that, on one level, it’s a no-brainer. Who hasn’t heard a parent tell—or been a parent who’s told—a child, “Eat your fruits and vegetables!” or “Fish is brain food!”? Rules about which foods we’re supposed to eat or not eat have been with us pretty much from the beginning. Even the sacred Hindu text the Bhagavad Gita, in which a young warrior is advised by an all-knowing god Krishna, talks about what to eat.

“There are three kinds of food as well,” Krishna advises. “Here are the distinctions among them:

“Foods that are the
sattvic
are drawn to promote vitality, health, pleasure, strength, and long life, and are fresh, firm, succulent, and tasty.

“Foods that please the
rejasic
are bitter or salty or sour, hot or harsh or pungent, and cause pain, disease, and discomfort.

“Foods of the
tamasic
are stale, overcooked, tasteless, contaminated, impure, filthy, putrid, and rotten.”

So there you go, diet advice from 5000 B.C.

With all that, we certainly think we know what we’re supposed to eat. We know too much refined sugar or grain or salt is bad for our general health, as are the wrong kinds of fat.

We may ignore all that, but we do know it. What few people realize is that most nutritional advice is based on one particular kind of research—large population studies. These wide-swath studies have, in fact, found that diets high in fiber generally protect against colon cancer and those high in vitamin C reduce the risk of stroke. Researchers can trace the amount of fat in the diet to the rate of breast cancer in a population and watch those rates change as people move from one food culture to another. Japanese women do not suffer from the same rates of breast cancer as American women do, but after just two generations of living here, Japanese-American women, on average, have the same breast cancer rates as any other ethnic group. Similar population—or epidemiological—studies have repeatedly found that high blood pressure is associated with an increased risk of heart disease and that obesity is linked to many chronic diseases.

Still, if you peer closer, such correlations can disappear. Studies that keep track of specific foods and specific people often fail to find any effect at all. Just a few years ago, the now-famous Women’s Health Initiative, the kind of giant, randomized, controlled clinical trial that’s considered the Rolls-Royce of research, failed to confirm that a low-fat diet prevented breast cancer, for instance.

Long-term studies of the antioxidants vitamins E and C and beta-carotene that looked at their effects on individual people also found they do not prevent heart disease, and similar studies failed to confirm that diets high in fiber ward off colon cancer.

Certainly, a few foods have been directly linked to health. If we have a serious deficiency in our diets, adding a specific nutrient helps—folic acid for pregnant women to prevent neural tube defects in babies, for instance.

But our modern Western diets, as junk-food-filled as they may be, are also astonishingly varied and rich, with low-cost, fortified, and abundant food. Most of us get what we need and do not have serious deficiencies that can be easily corrected by adding this or that nutrient.

In light of all this, can we really expect that a glass of wine or a plate of spinach will make any real difference? Or is our fate prewritten in our genes and we’re just fiddling around the edges or, worse, fooling ourselves?

And given such a dismal track record of food and overall health, can we possibly know anything about food and the brain? Can we figure out what we should put in our mouths to nudge our complicated neurons?

Until recently, this question was not even asked. For years, scientists believed diet had little impact on our brains because they thought most nutrients didn’t cross the blood-brain barrier. The blood-brain barrier is real. Cells lining blood vessels in the brain are packed close together to keep out certain large molecules and maintain a chemical balance. Some bacteria are barred, for instance, and infections in the brain are rare for that reason. Paula Bickford, a neuroscientist who studies nutrition at the University of South Florida and the James A. Haley Veterans’ Hospital, says that for a long time most scientists believed that even vitamin E did not cross the barrier. In one study Bickford conducted, in which she gave high levels of oxygen to rats to see if it would induce damage, one reviewer of her work asked her why she was wasting her time because “nothing could affect the brain.” And that, Bickford says, “was just ten years ago!”

And there were other roadblocks as well. Until recently, most believed the brain was on a downhill slalom course from our mid-twenties, losing as many as 40 percent of its cells as it aged. Why bother worrying about a brain that is programmed from the get-go to decay? Did anyone really think another forkful of carrots was going to stop that from happening?

Now, though, we know that much of that doesn’t hold up. The brain does not lose large numbers of neurons as it ages. Nutrients do cross the blood-brain barrier and are, in fact, essential for the brain. As a result, there’s now renewed interest in figuring out how we can tweak our blood—stir in some growth factors from exercise or maybe some special ingredient in this food or that—to benefit our brains.

As Mark Moss in Boston says, “We never thought what was happening in the body was getting to the brain. We thought that the brain was protected. But we are finding that the blood-brain barrier can be breached. Believe it or not, the circulation people never talked to the brain people and now we are talking . . . and it’s a big, big deal.”

By nature a conservative lot, scientists don’t like to put their money on something until they understand
how
it might happen, the mechanism. Scientists are more willing to look at the food-brain link now because they’ve identified ways it could work.

And what are the mechanisms by which food might bolster our brains? They involve the same substances touted for years in terms of overall health—antioxidants such as vitamins C and E, along with anything that acts as an anti-inflammatory, from fish oil to aspirin.

Why should we go there again? It’s a legitimate question. Some suggest that we need to pay even more attention to the brain and food because the brain uses so much energy (at rest it uses 10 percent of the body’s oxygen and in mental activity up to 50 percent), leaving it both sensitive to and in greater need of certain nutrients. Others don’t go that far, but say that we’ve oddly missed the boat by thinking that the brain does not react to what we eat.

“The brain is not
uniquely
sensitive but it is
sensitive
to what we eat,” says Bickford. “And now we’re realizing more and more that what you eat can affect cognition.”

The theory of antioxidants and aging has been around now for more than thirty years, and it’s intriguing that it’s now at center stage again—in research into the brain as it ages.

The idea goes like this: When our cells (including our brain cells) burn oxygen to make energy, a byproduct called a free radical is produced and thrown off. A free radical is essentially a molecule that’s missing an electron. And because it lacks that electron, it is unstable and wants to steal electrons from other cells. It grabs those electrons where it can, causing damage to other cells willy-nilly in the process. That damage is called
oxidative
stress and many believe it’s one of the main culprits in normal aging.

So eliminating as many free radicals as possible seems like a good idea. When we’re young, free radicals are often neutralized by another molecule, an antioxidant, in a continual repair program. But as we age—for reasons that are still not fully understood—that process becomes less efficient; the antioxidants can’t keep up with the hordes of free radicals (which are also produced by exposure to environmental insults such as pollution, ultraviolet light, and radiation), and more brain cells are left dented and nicked.

Then, a few years ago, another potential aging mechanism was identified: inflammation. Inflammation occurs when the body is injured and white blood cells rush in to do repairs. With that incoming surge, there can be collateral damage. Like fire engines driving up on a nearby lawn as they speed to a house to put out a fire, the cells rushing in to help out often harm surrounding healthy cells. And if the brain or the body is in a state of chronic low-level inflammation, there’s likely to be a buildup of damage. Unable to cope, cells—including brain cells—begin to shut down and die. Long-term inflammation (which many now believe can also come from chemical processes that accompany obesity or even excessive stress) may contribute to a number of chronic diseases, from heart disease to Alzheimer’s.

So, if the evil twins of brain aging are oxidative stress and inflammation, the questions are: Will eating foods high in
anti
oxidants or
anti
-inflammatory agents make a difference? Does it have to be real food or can it be a supplement or a vitamin pill? And can we make an impact on our very complicated brains if we start gorging on antioxidants and anti-inflammatories at middle age, or is that too late?

No one thinks a lack of antioxidants or too many inflammatory foods are the root causes of neurodegenerative diseases. But nearly everyone now thinks they are, at the very least, somehow part of the normal aging process in the brain, and therefore possible targets for intervention.

“My own view is that antioxidant damage and inflammation are in the background and they make cells more susceptible to other insults such as neurodegenerative diseases,” Bickford says. “If we get insults like that, we are less able to function at 100 percent and make repairs, then we start to see failures.”

Normal aging in the brain, many believe, comes about in part because repair mechanisms slow down. That process is complex but does seem to include antioxidant damage and inflammation, and both, Bickford says, “can be affected by nutrition,” including what we eat in middle age.

“When a cell is dead it’s hard to bring it back to life,” she says, “but certainly in middle age and up until the point of no return, I think there is room for repair.”

With all this new information, science has now embarked on a merry chase to figure out which foods give our brains the biggest bang for our buck. Several years ago, the U.S. Department of Agriculture, with researchers at Tufts University in Boston, developed a method to screen and rank foods for their antioxidant capacity. The list is known as ORAC, for oxygen radical absorbance capacity, and it’s one of the main reasons we suddenly started eating bowls full of blueberries. Just to give you the top twenty-five, the list goes like this:

Prunes, raisins, blueberries, blackberries, garlic, kale, cranberries, strawberries, raw spinach, raspberries, Brussels sprouts, plums, alfalfa sprouts, steamed spinach, broccoli, beets, avocados, oranges, red grapes, red peppers, cherries, kiwifruit, baked beans, pink grapefruit, and kidney beans. (A key to this is color—generally, darker is better.)

Down the list a ways are carrots, coming in at forty, and tomatoes, at forty-two.

So does that mean we have the answer? Have a hearty breakfast of prunes and kale and, if you’re not up for a glass of red wine (red grapes) that early, a cup of black tea (also high in antioxidants) and call it a day?

Not entirely. Despite a growing belief in the potential of foods such as blueberries and spinach to help stave off aging in the cells of the brain as well as the body, it’s important to remember that, in terms of the brain, there have been no long-term clinical trials in humans to test all this. Not one.

Most smaller trials of vitamin C or E or ginkgo biloba and cognition have been mixed at best. There are ongoing large human trials to see if curcumin, which is the turmeric found in a lot of Indian food (Indians have a lower rate of Alzheimer’s than some other populations), or even caffeine (which we all know can give a needed jolt to nerve cells), can help ward off Alzheimer’s. But there are no full-scale controlled trials to figure out whether what we eat can help us remember what movie we saw last night.