Food Is Information

8: Food Is Information, Brain Food

GENES LOAD THE GUN. LIFESTYLE PULLS THE TRIGGER.

The past chapters have revealed just how much our brains are affected by our diet and lifestyle choices. From the way our neurons communicate with one another to the birth and growth of new brain cells, our personal day-to-day choices are continually influencing what’s going on inside our brains. We will now see how these effects are controlled not only by our lifestyle choices but also by the interplay of our behavior and genetic predisposition. Let’s begin by addressing the delicate and highly complex theme of our genetic individuality.

As Dr. James D. Watson said back in the 1960s, “We’re not all equal, it’s simply not true. That isn’t science.” As the quote points out, it takes none other than the man who discovered DNA’s double helical structure to confirm just how complex, variable, and highly individual our genes are. This inherent individuality occurs in a substantial portion of our genome, giving rise to distinctive characteristics such as hair and eye color. These variations depend on the subtler genetic information carried in our DNA. Whenever you are looking into a loved one’s eyes, you are experiencing nothing less than a distinctive display of their signature genetics at work.

How this actually occurs is less obvious.

Our genetic variability is the result of thousands of years of continuous genetic mutations. A mutation is a permanent change in our DNA. For example, originally, all humans had brown eyes. But some six thousand to ten thousand years ago, a genetic mutation occurred that produced the first blue-eyed human. When this first happened, one can only imagine the sensation it caused! Since then, the blue-eye gene has spread the world over and today is considered a fairly common trait.

Genetic mutations have happened throughout the course of evolution. Some are positive, such as the mutations that ultimately led to the beauty of different eye colors or to the increased size and power of our brains. Other mutations are harmful and lead to disease. However, these “bad” genetic mutations are rare, affecting less than 1 percent of the population.

To sum it up, there are a handful of genetic mutations that can make us sick, and a myriad of genetic variants that simply make us different.

This is particularly true as far as our brains are concerned. The human genome sports an estimated 15 million variations, a large part of which involve brain function. Just imagine that each and every one of us carries at least some permutations of all these variations, and the term “diversity” assumes a whole new meaning.

Our brains possess something akin to a fingerprint. While the architecture of the brain, with its various partitions into functional areas and specific structures, might be roughly the same in all of us, there are large variations when it comes to brain size, shape, activity, and molecular composition. Such differences are not only based on our unique genetic makeup, but are shaped, molded, and written upon by our backgrounds, education, and experiences. Add to that the many foods we’ve been exposed to, our cultural environments, and all the places we’ve explored since the day we were born, and it only makes sense that no two brains could ever be alike.

This tremendous variability is never more evident than when viewing brain scans. I have been doing brain imaging for over fifteen years, inspecting and quantifying hundreds, if not thousands, of scans. Among them are those of the young and old and every age in between, those of men and women, those of the happy and the unhappy, of the healthy and less fortunate. In addition, I’ve studied equal numbers of scans showing the effects of neurological diseases like Alzheimer’s, Parkinson’s, or stroke. Not a single day goes by that I do not stand in awe at the uniqueness that each patient’s scan reveals, each one different and distinct from the next.

In the end, it is our unique genetic makeup, combined with our own lifestyle and behavior, that determines the fate of our brains, and therefore our chances of aging gracefully over the course of a lifetime—or of forgetting names and faces instead.

While it is true that one’s brain blueprint largely depends on the DNA it has received from its parents, recent discoveries have led to rethinking the old view that “you are your DNA” in favor of a much more dynamic model. In this new model, genes are pivotal in establishing some aspects of brain health, but it is our current, ongoing lifestyle choices that play a central role in turning those genes on or off. As strange as this might sound, you actually have the power to activate or silence your genes, and this discovery is called epigenetics.

Epigenetics refers to the fact that while your lifestyle choices won’t modify the structure of your DNA, they do have the ability to modify the way your DNA works. Where you live, who you interact with, how you exercise, which medications you take, and—yes, you guessed it—especially what you eat cause changes inside your body that in turn switch your genes on or off. This can occur once in a lifetime or continuously over time, thereby influencing your chances of retaining or not retaining optimal cognitive fitness.

What all this boils down to is that your DNA is not your destiny after all. The genetic lottery might determine the cards in your deck, but the way you are living your life deals you the hand you are actually playing. We’re back to where we started—genes load the gun, but lifestyle pulls the trigger.

SWITCHING OFF YOUR DNA

Among all the lifestyle factors that are known to have an impact on the action of human DNA, food is the one that plays a predominant role. Everybody exercises once in a while, takes medications now and then, or is exposed to environmental toxins on occasion (which all impact your DNA). But when it comes to food, we partake in meals each and every day, and several times a day at that, and we do this consistently over the course of an entire lifetime. It is this continuous exposure to food that makes diet the most important factor ever to affect our DNA.

Several studies have shown that some dietary nutrients have the ability to influence and regulate our DNA’s behavior. These happen to be the same nutrients the brain needs most, such as omega-3s, choline, several antioxidants, and B vitamins. Over the past decade, this realization has prompted nothing short of a revolution in the nutrition field. It has in fact become clear that the effects of nutrition on health can only be fully appreciated with a deeper understanding of how nutrients act at a genetic and molecular level.

The interaction between food and genes has become the major focus of a new discipline called nutrigenomics, which aims at revealing how food directly influences DNA activity. This novel perspective has brought new meaning to the old adage “We are what we eat” by demonstrating that what we eat is busy determining what we are to become. At the same time, our genes affect our reaction to food as well, making us receptive to certain foods and intolerant of others.

It turns out that diet, far from merely being a source of fuel or sustenance, is instead a “genetic on/off switch.” Some foods directly influence our DNA by turning on the good genes that make us more resistant to disease, while others turn off these same genes, making us more likely to get sick.

This is because food is information. Dietary nutrients are nothing less than biological signals that, upon entering our systems, are “read” by your cells. Believe it or not, your cells are coded with detectors that are busy searching for specific nutrients. Let’s say they spot healthy omega-3s entering your bloodstream via your meal. Once they do that, they let your DNA know that help is on the way. Then it’s as if your DNA takes a deep breath and slows down the body’s production of other anti-inflammatory compounds as a result. This is just one example of how a common dietary ingredient can powerfully influence your genes. Depending on whether a nutrient is considered friend or foe, a corresponding genetic response will be cued accordingly.

Whether we look at how food affects our genes or how our genes affect our reaction to food, this new, burgeoning science has thrown open the doors to our genetic individuality being key when it comes to how we approach health and nutrition. As a result, the age of a one-size-fits-all approach is fast becoming a thing of the past. Instead, we stand at the forefront of a new, personalized approach to our health, and in turn, our nutrition.

BIO-INDIVIDUALITY

These discoveries point out that there is not one perfect way of eating that will work equally well for everybody. This concept, often referred to as biological individuality, is an idea currently gaining unprecedented respect and interest in the medical field.

Bio-individuality insists on the fact that each human being has a unique biochemistry that influences behavior, mental health, hormonal production, allergic tendencies, immune capacity, and of course, nutritional needs. Because of the genetic differences in the ways our bodies process food, some of us are naturally deficient in some nutrients while possessing an overabundance of others. As the proverb goes, “One man’s meat is another man’s poison.” Indeed, it was recently discovered that many human genes have a heightened sensitivity to diet.

This is true both for the individual and for certain populations. Lactose intolerance is a perfect example. Many people are lactose intolerant, which means that they have difficulty digesting lactose, a type of sugar contained in milk. This happens because they lack an enzyme called lactase, which is responsible for breaking down lactose. Since humans digest mother’s milk as infants, the gene that produces lactase switches off on its own post-weaning.

However, once humans began herding cattle, being able to digest cow’s milk as adults became an evolutionary advantage. Milk is a good source of fat and protein, as well as calcium, vitamin D, and several B vitamins including the brain’s beloved choline. Some populations adapted to this by keeping the lactase gene turned on and thus continuing to produce lactase in their bodies throughout adulthood. Other populations that were not dependent on cattle (such as some parts of China, Thailand, and Africa) did not develop this ability. To this day, people who stop producing lactase after weaning are lactose intolerant as adults.

At an individual level, we find even more varied and unpredictable differences. As a result, we are each genetically unique in the way we process our food. For example, some people are naturally less efficient at assimilating brain-essential nutrients such as vitamin E, some B vitamins, or omega-3s. Others have difficulties controlling trace minerals like copper, iron, and zinc. Still others have insufficient levels of stomach acid or impaired intestinal function and have trouble digesting their food. Making things more complex yet is the fact that we each have a different microbiome.

MEET YOUR MIGHTY MICROBIOME

The term “microbiome” refers to the collection of bacteria, viruses, fungi, and other microbes that inhabit the human body.

Just like planet Earth has its own ecosystem filled with animals, plants, and all sorts of organisms, the human body hosts a complex ecosystem of its own, which is home to a fantastic diversity of life. Of this ecosystem, very little of it actually belongs to our species. All sorts of microbes can be found thriving upon our skin, inside our mouths, and along all the body’s various nooks and crannies. They have a particularly large stakeout in the GI system. The body of an adult human harbors nearly 100 trillion bacteria, with more than 95 percent of them located in our gut.

Scientists have long known that bacteria reside within humans, but their presence and relevance remained underappreciated until the discovery of the microbiome. It turns out that in our bodies, bacterial cells outnumber human cells by about 10 to 1. In other words, up to 90 percent of our cells are non-human. Even though bacterical cells are much smaller than ours, ninety percent is a lot of cells. If you grouped them together they would be about the size of a football and weigh up to 3 pounds.

Not only are there millions of bacteria residing inside us, but these bacteria derive from thousands of different species, each equipped with their own genetic material. As a result, we are literally inundated by non-human DNA. It is nothing short of mind-blowing that the human genome (aka our DNA) is extremely small as compared with that of these much simpler organisms. Our DNA comprises about 23,000 genes, while the microbes inhabiting our bodies are representative of an incredible 4 million distinct genes of their own.

This raises a whole range of thought-provoking existential and scientific questions, not the least of which is: Should we be worried?

Some microbes, especially viruses, can definitely harm humans. For example, some viruses give us measles and the flu. Some bacteria can also be detrimental, like when they cause strep throat or food poisoning. But in reality, fewer than 1 percent of bacteria causes disease in humans. The vast majority are not only harmless but downright helpful. As it turns out, our gut microbes are major players in our overall health, literally from head to toe.

First and foremost, they help us digest food, each one having the ability to absorb various nutrients to a greater or lesser degree, and each one reacting differently to the foods we eat. For instance, our capacity to absorb vitamins like B12, along with several minerals essential for a healthy nervous system, is highly dependent on the health and diversity of our gut microbiome. Moreover, these friendly bacteria are able to produce essential vitamins like folate and also help maintain adequate levels of amino acids like tryptophan, which is in turn necessary to produce neurotransmitters like serotonin.

Additionally, our gut flora produces fatty acids that are beneficial for the body, like butyrate, an excellent source of energy for our muscles. But what is particularly surprising about these bacteria-made fatty acids is that they can directly alter the function of the blood-brain barrier, the cellular fortress protecting the brain against infections and unwanted pathogens. The fatty acids produced by our gut microbes can both strengthen the barrier and make it more lax, effectively regulating how many nutrients and foreign substances can pass through the brain’s defense system.

Last but not least, our gut flora acts as a mighty warrior for the immune system, defending us against disease-causing microbes. There is a delicate balance between the gut’s strength in keeping out the bad guys while at the same time managing to absorb and harbor the good guys. In general, the intestinal lining must be permeable enough for nutrients and other molecules to both enter and exit the intestine. However, if the lining becomes too permeable, “leaky gut” can occur. In this case, the space between cells opens up too much, allowing leakage of intestinal contents, such as large food molecules or bacteria, into the circulation. When our body senses these foreign invaders in our bloodstream, it triggers an inflammatory response, one aimed at escorting the intruders back out. In the long run, the inflammatory response aimed at defending us from the bad guys can backfire, damaging our intestinal cells and microbiome, too, making the gut even more inflamed and leaky. This vicious circle further impairs the system’s ability to absorb the proper nutrients, leaving it vulnerable to food sensitivities or allergies. If this weren’t disturbing enough, as we’ll see in the next pages, the brain is potentially at risk of being affected as well.

BUGS AND BRAINS

Recent studies have revealed that alterations in the gut microbes can influence the risk of brain disorders such as autism, anxiety, depression, and even dementia. This has resulted in increased attention to the concept that a healthy gut is critical to a healthy brain.

I can only tell you the beginning of this story because the story has only just begun. While there’s been an explosion of research on the microbiome with regard to brain health in recent years, this field is still in its infancy. It is also important to underline that most microbiome research so far (including antibiotic treatment or even fecal transplants) has been largely based on experiments using rodents. Given the huge differences between mice and men, there is no guarantee that these findings will hold up in humans. That said, some initial studies done on humans support the existence of a relationship between the world of the microbiota and the health of our brains. This initial research has triggered tremendous interest by the professional and lay media, not to mention national funding agencies, leading to a justifiably meaningful shift in the way we view many brain diseases.

Historically, the gut and its collection of microbes have been largely ignored by Western neurology and psychiatry. To this day, students are taught that the brain is anatomically isolated and well guarded by the blood-brain barrier that keeps out pathogens including bacteria. There are some exceptions, like when such pathogens happen to bypass the blood-brain barrier causing disease, as in the case of meningitis. But for decades, scientists thought of microbes as either fairly harmless things hitching a free ride through our bellies (which therefore had nothing to do with what was happening inside our brains) or direct threats to our well-being that had to be gotten rid of.

This view has dramatically changed, as a number of new studies have shown that our gut bacteria not only influence how people eat but also how we think and feel.

Some of the most convincing work in this regard has been done on anxiety and depression. For instance, animals genetically engineered to be without a microbiome (the so-called germ-free mice) have increased anxiety-like behaviors and an exaggerated response to stress. They also demonstrate bizarre behaviors, tend to be antisocial, exhibit memory problems, and even show reckless tendencies. However, scientists found that they could stabilize the animals’ behavior by supplying them with friendly bacteria. This not only lowered their stress levels but also directly increased production of GABA (the neurotransmitter that calms nervous activity) in their brains.

Additionally, the microbiome turned out to be closely involved with neuro-development. For decades, doctors and parents alike have noted that anywhere between 40 percent and 90 percent of children with autism also demonstrate some GI symptoms, such as food allergies and digestive issues. Recent studies are showing that there might indeed be a connection with issues present in the child’s microbiome. For instance, some of the symptoms expressed by germ-free mice, such as limited social interactions, a tendency toward repetitive behavior, and a reduced communication with their peers, are similar to human autism. Treating these “autistic” mice with Bacteroides fragilis (a bacterium that is sometimes reduced in children with autism) improved the animals’ behavior. It made them less anxious, more communicative with other mice, and less prone to showing repetitive patterns.

As you might have noticed, all the research reviewed so far was carried out on lab animals. However, there is some evidence that probiotics (i.e., live microbes that reside in your gut and benefit the host, aka you) can alter brain function in humans as well.

One of the best-known studies to date used functional MRI (fMRI) to test whether eating probiotic foods like yogurt would elicit changes in brain activity in a group of young participants. Functional MRI is a brain imaging technique that measures changes in blood oxygen levels as a proxy for neuronal activity. This method gives us a snapshot of those brain regions that get activated (or not) in response to different forms of stimulation. In this study, twenty-five healthy women were divided into a group who ate a cup of probiotic yogurt twice a day for a month and a control group who did not eat any yogurt. All participants were then shown upsetting pictures of people with angry, sad, or frightened facial expressions to gauge their emotional responses while being monitored with fMRI. Perhaps surprisingly, there were significant differences in the way yogurt eaters and non–yogurt eaters reacted to this test. The former showed a more moderate response in the face of negative emotional stimulation as compared to the latter. In other words, they were able to remain calmer than those who were without the probiotic supplementation. Wouldn’t it be great if doctors prescribed yogurt instead of Xanax?

Besides the microbiome’s role in influencing anxiety and stress levels, new research indicates that it might be a preeminent factor in determining brain longevity. Over the course of a lifetime, people who consume a diet high in fiber and low in animal fat (animal fat does not agree with our friendly gut flora) have the healthiest microbiomes. On the contrary, the microbiome of those whose diets are low in fiber but high in animal fat are very fragile and tend to easily collapse. These findings suggest that the lessening of healthy gut bacteria could contribute to the cognitive decline observed in old age.

Many people are even wondering whether dementia itself could be due to bacterial infections or malfunction. As of today, there is no clear evidence that an unhealthy microbiome would in and of itself cause dementia. Nonetheless, many viruses and bacteria can profoundly affect the brain, generating symptoms like confusion, brain fog, and memory loss. For example, the human immunodeficiency virus (HIV-1) that causes AIDS can also cause a form of dementia known as “HIV-related dementia” with symptoms that mimic those of Alzheimer’s. The herpes simplex virus that causes sores around the mouth can trigger brain inflammation (encephalitis), thus eliciting cognitive and mood disturbances. Syphilis, a well-known bacterial disease contracted chiefly by infection during sexual intercourse, can spread to the brain and lead to severe cognitive impairment. Because of their ability to affect cognitive health, these pathogens are routinely screened for in the evaluation of dementia.

When I was at NYU, we had an interesting experience with a woman referred to us with a diagnosis of MCI, often a prodromal stage to Alzheimer’s. She was literally terrified at the thought that she might end up developing dementia, as her mother had died of it just a few years prior. After running several blood tests, our medical director spotted something unusual: the patient had a massive yet completely asymptomatic UTI (urinary tract infection). She reported no pain, no irritation or itching—despite the fact that her urine was full of bacteria and blood cells. Needless to say, antibiotic treatment was initiated immediately. When the patient returned to complete her evaluations a few months later, she received a diagnosis of normal cognition. You can just imagine her relief at being herself again, with no Alzheimer’s in sight.

In the end, even though the data is still limited, it seems to point to the fact that the microbiome is involved in several aspects of brain health and behavior. This raises hope that optimizing our diet and lifestyle to favor healthy gut bacteria might also be a viable strategy to manage, or even prevent, anxiety, depression, and autism, as well as the cognitive changes that might occur with aging. But how exactly are we to do that?

GOOD HABITS: PREBIOTICS, FIBER, AND FERMENTED FOODS

First and foremost, our gut health relies on regular consumption of both prebiotic and probiotic foods.

Prebiotics are literally food for your body’s good microbes. This is because these foods are particularly rich in a distinctive kind of carbohydrate called oligosaccharides, which happen to be your gut flora’s favorite meal. These carbs are unique in that, while all other carbs are broken down in the small intestine, oligosaccharides can’t be digested there and consequently flow down to the large intestine virtually untouched. Here, they play the critical role of feeding our friendly bacteria and keeping them healthy. These bacteria-supportive carbs come from foods that are not particularly sweet but do have an ever-so-slightly sweet aftertaste, such as onions, asparagus, artichokes, and burdock root. You can also find prebiotics in garlic, bananas, oats, and milk.

Besides nourishing our friendly bacteria, certain oligosaccharides are drawing increasing attention because of their cholesterol-lowering, cancer-fighting, and detoxification effects. These include the beta-glucans found in mushrooms (reishi and shiitake mushrooms have shone in many studies) and the glucomannans abundant in aloe vera juice. I’m a big fan of both, so expect to hear more about these foods in the next chapters.

Additionally, fiber-rich foods are crucial to our microbiome’s well-being by supporting digestive health and regularity. A healthy digestion is key to removal of waste products, harmful toxins, and bad bacteria—all of which can harm our gut flora. Cruciferous veggies like broccoli, high-fiber fruit like berries, and all kinds of leafy greens, as well as legumes and unsugared whole-grain cereals, are good examples of fibrous foods we should consume on a regular basis to ensure proper gut health.

Besides prebiotics and fiber, our gut microbes crave probiotic foods. These foods contain live bacteria (probiotics) that, upon reaching the intestine, replenish our microbiome’s good guys. Probiotics are naturally provided by fermented and cultured foods, including fermented milk such as yogurt and kefir, but also pickled vegetables like sauerkraut. More specific recommendations are included in chapter 12.

BAD HABITS: ANTIBIOTICS, MEAT, AND PROCESSED FOODS

In addition to knowing what to add to your diet and lifestyle, it’s equally important to know what to avoid. Any foods and agents that are disruptive to your gut’s health, either by increasing its permeability or by causing inflammation, can also decimate your microbiome in the process.

Antibiotics are the first entry on the microbiome’s Most Wanted list. The microbiome is negatively affected by the overuse of antibiotics, since antibiotics are not fussy and inadvertently kill our good microbes along with the bad ones. Up until World War II, when medical conditions like pneumonia and wound infections could often prove fatal, antibiotics were a major success. However, they have since become overprescribed in many countries, leading to a pandemic of antibiotic-resistant disease. At the same time, there is the added complication of their having diminished both our microbiota’s stability and its diversity.

I am not by any means suggesting that you should avoid taking antibiotics when you need them. However, many Americans take antibiotics as a quick-fix measure or even “just in case.” For example, I have heard people say, “I have the flu, I need antibiotics.” Contrary to popular opinion, that’s not necessarily the case, as the flu is often caused by viruses, not bacteria. Discuss this with your doctor the next time you feel under the weather. Incidentally, most European doctors recommend eating yogurt (or taking a probiotic supplement) before or with your antibiotics to protect your GI tract and at the same time replenish your bacterial pool.

After medicines, food is the major factor influencing our intestinal function. While antibiotics might enter our bodies only once in a while, food is constantly altering the status and health of our gut microbes. Of all foods known to have a negative impact on our microbiome, commercially raised meats top the list.

Believe it or not, meat can be a major source of deadly “superbugs.” Animals raised in confined animal feeding operations (CAFOs)—which is the norm in modern-day factory farming—are routinely given low doses of antibiotics to prevent diseases caused by the crowded and unsanitary conditions in which they are forced to live. In fact, of all the antibiotics sold in the United States, as much as 80 percent of them are used to treat livestock instead of people! The problem is that when we eat the meat, we also ingest the antibiotic. As a result, for many people meat is the primary source of antibiotic overload.

What’s worse, half of all the meat sold in American grocery stores harbors drug-resistant bacteria that can cause severe food-borne illnesses. According to a recent study by the U.S. Food and Drug Administration (FDA), antibiotic-resistant strains of Salmonella and Campylobacteron were found in 81 percent of ground turkey, 69 percent of pork chops, 55 percent of ground beef, and 39 percent of chicken meat all across the country. Even more disconcerting, federal data shows that 87 percent of all meats tested positive for Enterococcus bacteria and Escherichia coli (E. coli), which means that the meat had at one point come in contact with fecal matter.

This is one of the many reasons why I recommend eating only organic, grass-fed, free-range, or pasture-raised meat, dairy, eggs, and other animal products, since organic standards do not allow non-medical use of antibiotics.

Processed foods are another major threat to our gut. Besides being high in unhealthy sugars, such as high fructose corn syrup and refined white sugar, processed foods often contain emulsifiers, which are particularly detrimental to the microbiome. Emulsifiers are food additives used to improve the texture, appearance, and shelf life of many foods, and are included in everything from ice creams to baked goods, salad dressings, creamers, and dairy and nondairy milks (yes, even your “healthy” almond milk can be bad for you if it contains emulsifiers). It turns out that these substances can increase permeability in the gut lining, causing an influx of bad bacteria into the bloodstream. This in turn can cause colitis and intestinal inflammation such as irritable bowel syndrome (IBS), as well as the metabolic dysfunctions that can lead to obesity, high blood sugar, and insulin resistance.

Next time you go grocery shopping, take a closer look at the ingredients label on any packaged foods you pick up and check for these common food additives: lecithin, polysorbates, polyglycerols, carboxymethylcellulose, carrageenans, xanthan gum, guar gum, propylene, sodium citrate, and datem of mono- and di-glycerides. These are all red flags on our path to optimal cognitive fitness.

GLUTEN: IS IT REALLY AS BAD AS WE FEAR?

Last but not least, let’s talk about gluten. Gluten is a protein contained in a variety of grains including wheat, rye, and barley, which has made the headlines lately with regard to having potentially harmful effects on brain health.

There are many things we don’t yet know about gluten consumption and its effects on human health. What we do know is that gluten can have a negative effect on gut health. Some people have particularly strong reactions to it, especially those patients with celiac disease who are genetically susceptible to gluten and must avoid foods that contain it. In these patients, gluten causes increased intestinal permeability, creating the leaky-gut environment described earlier, with subsequent symptoms of a weakened immune system and inflammation. Similar reactions are sometimes observed in people who don’t have celiac disease, possibly due to negative interactions with their microbiome. In the end, the way your gut reacts to gluten depends on your DNA, both human and microbial, so you need to listen to your body and respond accordingly.

It is much less clear whether gluten is in any way connected with brain health. I’m often asked if gluten is bad for your brain and if it should be avoided. Currently, there is no conclusive evidence of a connection between gluten consumption and cognitive decline or dementia. To check on this yourself, you can use the same tool scientists use to look for peer-reviewed publications: PubMed (www.ncbi.nlm.nih.gov/pubmed). If you search “gluten and Alzheimer’s or dementia,” you will find the most current information on the subject. Be careful to include only journals with English titles, such as the Journal of Alzheimer’s Disease or Neurology. As of March 2017, there are only ten papers or so that look into the relationship between gluten and cognitive disorders, mostly with regard to patients with celiac disease. To give you a sense of what scientists consider a much more significant finding, run a search on “glucose and Alzheimer’s or dementia” instead. With this pairing, you’ll find close to four thousand papers that report significant and beneficial associations. Given the relationship between the gut and the brain, further clues might come up in the future as more scientists start looking into gluten as a possible risk factor for cognitive impairment. For the moment, the jury is still out. What I can tell you is that so far there is no evidence that eating grains will make you forget names or lose your keys.

While gluten has not been proven to harm our brains, the absence of fiber has. There is plenty of evidence that fiber deficiencies negatively affect the microbiome and therefore, to some extent, the brain. As previously discussed, we also need fiber to stabilize our blood sugar levels and to support a healthy immune system. Since gluten is found in the many grains and cereals that contain fiber, eliminating gluten from the diet stands to compromise an adequate fiber intake. As such, I recommend caution before eliminating grains from your diet. Here’s my commonsense approach: find out what works for you. If you are among those who tolerate gluten, carefully chosen, organic, non-GMO whole-grain foods are an important addition to a gut-healthy, and subsequently brain-healthy, diet.

But if you’re concerned, speak to your doctor about being tested for gluten allergies or sensitivities. Should you turn out to have a negative reaction to gluten, by all means watch your gluten intake. It’s important to assess our choices wisely. In this case, naturally gluten-free grains include amaranth, buckwheat, millet, rice, sorghum, teff, and quinoa (technically, quinoa is a seed). Tofu is also naturally gluten-free—but your average soy sauce is not. What most people don’t realize is that gluten is present in many foods and products besides grains. Take a look at Table 8 for a list of the many unexpected yet common places we find gluten.

As we reach the end of this chapter, the bottom line is: every person’s diet should reflect their genetic uniqueness with the goal of optimizing their health and mitigating risk of disease. Although this field is just developing, we already have the necessary tools in place to assess the effects of various foods on our DNA, human and non-human, and how their interactions support or affect our brains. Also keep in mind that nutrients alone won’t achieve our aims. So many of our anxieties around diet take the form of our search for the perfect nutrient, the ultimate superfood, or the one magic pill that will cure all our ills. We tend to obsess over the specific qualities of various foods and supplements, mull endlessly over proteins versus carbs versus fat, and debate which fish oil supplement to take. But as we’ve learned, no matter what we seek, the answer ultimately lies in the nutrients existing in unadulterated versions of the foods we eat. And they can only reach us when we actually pick up the food and eat it. How we eat and how we approach food is really what matters. In order to change our diets, we can begin by relearning the art of eating, which is a question of lifestyle as much as it is nutrition.

Our next step is to take a closer look at those who have indeed mastered the art of eating right for their brains as well as for their overall well-being. Let’s turn now to those that are the exception to the rule: the centenarians.

Food ItemExamples
Grain cerealsWheat, rye, barley, oats (unless gluten-free)
Wheat derivativesWheat berries, durum, semolina, farina, farro, graham
Malt and malt derivativesMalted barley flour, malted milk or milkshakes, malt extract, malt syrup, malt flavoring, malt vinegar
PastaWheat pasta, raviolis, dumplings, couscous, gnocchi, noodles (except rice noodles)
Baked goodsBread, pastries, crackers, cookies, croutons, pizza
Breakfast foods (often contain malt extract/flavoring) Breakfast cereal (including corn flakes and rice puffs), granola and granola bars made with regular oats, pancakes, waffles, French toast, crepes, biscuits, granola bars
Sauces, gravies (often contain wheat flour as a thickener)Soy sauce, cream sauces made with a roux
Processed meats Deli meat, cold cuts, pastrami, salami, bologna
CondimentsSalad dressings, marinades, mayonnaise, ketchup
Fried foods (often made with batter containing wheat flour)French fries, fried chicken, chicken nuggets, fast foods, doughnuts, fried baked goods
Candy and candy bars
Creamers and nondairy creamers
Soup, commercial bouillon and broths
Meat substitutes made with seitan (wheat gluten)Vegetarian burgers, vegetarian sausage, imitation bacon, imitation seafood
Eggs served at restaurants (might contain pancake batter)Omelets, scrambled eggs, frittata
BeveragesBeers, ales, lagers, malt beverages that are made from gluten-containing grains, wine coolers, vodka (unless gluten-free)
Drug fillers (often contain starch)Some drugs, over-the-counter medications and dietary supplements
Lipstick, lip gloss, and lip balm (often contain starch)
Any foods cooked in shared food-preparation equipment (pasta pot, toaster, deep fryer)

Table 8. Common gluten-containing sources and where to find them.