CHAPTER 1

Your Brain on Food

WHEN I THINK OF THE BRAIN—my brain, anybody’s brain—I’m both dumbfounded and astounded: Dumbfounded because essentially a lump (three pounds) of mostly (60 percent) fat can be the seat of our emotions, our heartbeat, our memories, our respiration, our learning, our consciousness, and, perhaps, our soul. Astounded because among that fat lie some 100 billion brain cells (neurons). If you want to wrap your head around that number, think, as neuroscientist Frank Amthor notes, of all the stars in our galaxy—including the ones you can’t see with the naked eye—and you’re getting close. Kind of. Maybe. If that isn’t enough, each neuron talks to others using numerous branches called dendrites and axons; if you want an image, recall those old-time movies where there was a switchboard operator plugging line “A” into “your party”—line “B”—and, well, there’s a stick figure drawing of your brain in action.

That the brain and its function has long been a mystery is no mystery. From the Bible through the Renaissance, from Socrates to Shakespeare to today, our great minds found their understanding of the brain’s properties to be as ethereal as gossamer wings. “Everything we do, every thought we’ve ever had, is produced by the human brain,” says astrophysicist Neil deGrasse Tyson. “But exactly how it operates remains one of the biggest unsolved mysteries, and it seems the more we probe its secrets, the more surprises we find.”

Many of those surprises come in the scientific connections between food and the various workings of the brain. Type “food and brain” into the National Library of Medicine’s encyclopedic database and you come up with roughly 32,000 peer-reviewed studies—and the curve is clearly accelerating as nearly half of those studies have occurred in the past ten years. Food and mood, food and memory, food and learning—all are being investigated, and there’s a growing body of evidence suggesting that what we eat either primarily affects our brain or has secondary effects (for example, whatever you eat that’s heart healthy also may lower the risk of stroke, which is definitely a brain condition).

Here we take a look at some of those food-brain connections.

Stress, Anxiety, Depression, and Food

Let’s face it: most of us don’t treat our brains with kid gloves. Between blowing off sleep, multitasking to the max, and eating poorly, we put our brains under a tremendous amount of stress. Now, our brains are equipped to handle stress through a mechanism called the fight-or-flight response. When the stress happens suddenly (like when you’re driving along and you slam on the brakes to avoid an accident), what you notice, after you’ve done a body check, is that your heart is pounding, your mouth is dry, and you’ve broken out into a sweat. That’s the result of the hypothalamus—an area deep in your primitive brain—sending out a signal to the adrenal glands to essentially “pump up the volume” and shoot a hormone called cortisol, and a few neurotransmitters like norepinephrine and dopamine into your system.

Cortisol et al. are what allowed your ancestors to outrun a saber-toothed tiger (for at least a few seconds, until they reached safety), and, in the modern world, make for those occasional sensational headlines like “Wife Lifts Car Off Husband.” But the fight-or-flight response—and our adrenal system—was never intended to be on full time. That way lies burnout and more. Researchers at Emory University noted that depressed people often had extremely high levels of cortisol in their blood. Another study from Canadian researchers published in Brain and Cognition showed that stress hormones negatively impacted cognition, our ability to process and remember information. If stress continues long enough, it can, as the Latin root of the word distress suggests, “pull us apart,” destroying brain cells in the hippocampus, the memory-creating center of the brain.

Fortunately, to a great degree we can combat stress. Exercise and mind-body work such as yoga and/or meditation certainly help. And food can be a great boon to relaxation. Now here’s where you need to follow the bouncing ball. When cortisol floods the body constantly, it causes the body to break down the amino acid tryptophan more rapidly. This is decidedly not a good thing for your mood, because the higher the levels of tryptophan that stay in the body, the more tryptophan there is to convert into—wait for it—serotonin. Serotonin is the brain’s happy hormone. So, under certain conditions, more tryptophan = more serotonin = better mood. I say “certain conditions” because just eating a ton of turkey (like at Thanksgiving dinner) won’t do the trick, because tryptophan is just one of many amino acids vying for the brain’s attention and absorption. What you’re looking for is foods that have a high ratio of tryptophan in their overall amino acid profile, which increases the odds that tryptophan will make it through the so-called blood/brain barrier and be usable by the brain. You’ll find that in, of all places, pumpkin and sesame seeds (which, not coincidentally, are in this book). Another way of keeping tryptophan in the system is by making sure you get a larger proportion of vegetables on your plate with each protein-filled meal. According to nutrition expert Dr. Michael Greger, the carbs in plant foods are known to cause an insulin release that, Greger writes, “causes our muscles to take up many of the non-tryptophan amino acids as fuel, potentially leaving our tryptophan first in line for brain access.”

Another mood enhancer may be omega-3 fatty acids. These are found in cold-water fish, such as wild salmon, and in walnuts. Researchers looking at Japanese culture noted a marked lack of depression (as much as 90 percent less than among Americans); they also discovered that the Japanese, on average, ate fifteen times more omega-3s than Americans. Investigators in a large study in Montreal found that supplementing the diet with omega-3s brought relief to some patients with major depression who did not have anxiety issues. Other investigators, including Dr. Andrew Weil, cite a diet rich in anti-inflammatory ingredients, such as sardines and extra-virgin olive oil, to be helpful in reducing depression, and Ohio State researchers found that fighting inflammation with omega-3s lowered anxiety in some students.

Memory, Cognition, Learning, and Food

If there’s ever been an elephant lurking under the living room rug, it’s the topic of memory, especially faulty memory. It wasn’t long ago that experiencing a fading memory as one aged was considered inevitable. But that notion is undergoing a critical review, driven by a concept called neural regeneration (aka neurogenesis). Scientists for decades believed that the adult brain was incapable of adding new brain cells, or neurons, to replace those that were damaged or had died off. Recent discoveries have many of them now thinking the opposite: that new cells can be produced, notably in parts of the brain, such as the hippocampus, connected with learning. (Interestingly from a food viewpoint, the other area of the brain that appears to generate new neurons throughout life is in the olfactory bulb, which is where our sense of smell resides.)

Can we supercharge this regeneration process through food, and preserve our minds? Research is suggesting it’s possible. For example, consuming omega-3s is linked to greater activity of a chemical known as brain-derived neurotropic factor (BDNF). BDNF is believed to be responsible for kick-starting the growth of new neurons. A Spanish study found that, in addition to omega-3s, foods rich in vitamin E and flavanols (such as nuts and seeds, broccoli, and citrus fruits) increased BDNF levels, as did following a Mediterranean diet rich in walnuts and almonds. As to where you should get your vitamin E—pills versus food—Dr. Neal Barnard is adamant you go with the latter. “Vitamin E is protective,” he says, “but in a pill it’s only generally one form, alpha-tocopherol; but if you eat walnuts, you get all seven forms.”

Diet may also help counteract naturally occurring molecules within the body that attack memory and cognition. One such molecule is homocysteine, which is a by-product of the protein-building process. A study of 1,140 people aged fifty to seventy in Baltimore found that higher homocysteine levels were “associated with worse function across a broad range of cognitive domains.” The antidote may be increasing your intake of vitamins B₆, B₉ (folate), and B₁₂. Oxford researchers found that when they gave this vitamin regimen to people with mild cognitive impairment, their homocysteine levels dropped greatly and, over a two-year period, their cognitive testing scores jumped by up to 70 percent.

And again, don’t forget exercise. University of Pittsburgh neuroscience researcher Kirk Erickson notes that “exercise activates neurotransmitters and growth factors that affect new neurons in the brain. Exercise can influence gene expression.” He adds, “Throughout our lifespan our brain remains plastic, modifiable, and the things we do in our life, exercise and what we eat, affect the health and plasticity of the brain.”

The Mighty Methylators and Detoxification

The B vitamins, notably B₆, B₉, and B₁₂, also play a huge role in the process known as methylation, which controls the expression and repair of our DNA. Deficiencies in these B vitamins can lead to breakdowns in methylation and thence to improper DNA expression and repair, which in turn may help cause a whole host of mental issues including “depression, pediatric cognitive dysfunction, dementia, and stroke,” says Dr. Mark Hyman. He adds that methylation is “the key to detoxification,” because the process keeps a major player in detoxification, the super antioxidant glutathione, circulating in the body. Hyman also notes that methylation reduces inflammation and keeps neurotransmitters balanced. His suggestion to keep methylation functioning well is to consume plenty of dark, leafy greens, including kale, Swiss chard, spinach, and collards.

And Now a Word from Our Second Brain …

And you thought you only had one brain? Au contraire. Columbia University professor Michael Gershon came up with the term “the second brain” to describe the actions of the gut and enteric nervous system (ENS). The description is apt, for just as the brain in our head has neurotransmitters and nerve cells, so too does the gut—in the enteric nervous system. (The word enteric means “of or having to do with the intestines.”)

The fascinating thing about the ENS is that though it works to control much of the digestion in your gut, it definitely is impacted by what’s going on in the brain inside your head. The two are connected by the vagus nerve, which winds from the brain stem through to the abdomen. The vagus nerve controls our parasympathetic nervous system (PNS), which rides herd, along with the ENS, on digestion. There’s another nervous system, the sympathetic nervous system (SNS), which controls the aforementioned fight-or-flight response. The important thing to remember—at least when it comes to digestion—is that when fight-or-flight is engaged, it shuts down digestion (which makes sense: if you’re running for your life, you don’t have time to chow down, or energy for any metabolic function that’s not going to save your life this very minute).

Under normal, relaxed conditions, just thinking about food is enough to get our digestion rolling, as anyone who has ever opened a menu, read a few words, and found their mouth watering can attest. This so-called “cephalic” stage of eating is amazing. “You may secrete as much as 40 percent of the hydrochloric acid and digestive enzymes needed to break down the foods you eat before you consume a single ounce of food,” write Dr. Gerard Mullin and Kathie Madonna Swift.

But when we’re stressed, and the sympathetic nervous system has the upper hand, signals to the vagus nerve get disrupted, and digestion all down the line suffers. When stress is chronic, a dangerous cycle begins as we try to take in the nutrients we need for a healthy body and brain (that’s why you’re reading this book, yes?), yet stress impairs our GI tract and keeps it from assimilating those very nutrients. Acid reflux, irritable bowel disease—these may well be the result if you’re not treating your second brain very well. As a consequence, your first and principal brain suffers. So do both your brains a favor: before you eat, take a moment, and a few deep breaths. Then let the eating—and healing—begin!

Brain Science and Mindful Choices

It’s easy to get overwhelmed by the sheer volume of science surrounding the brain and food. Even I get dazed trying to wrap my head around all the studies and new information that seem to be coming out on an almost daily basis. My advice? Take the science with a bit of a “gee-whiz!” approach as opposed to thinking, “I have to understand this all, right now!”

I experience the science as both engaging and motivating: I’m excited that so many researchers are interested in this field, and I’m thrilled that food and cooking may really make a difference in how our minds function. Now it becomes a matter of getting behind the stove and doing it, and I’ll be with you all the way.