If you asked me ten years ago where the next revolution would be in medicine and, in particular, brain health, never in my wildest imagination would I have said “gut bugs.” But it’s true: today’s leading edge of science is establishing a link between healthy brain function and healthy gut function. It turns out that the gut is where a community of microbes collectively known as the microbiome thrives, collaborating with our physiology with every breath we take, beat of our heart and firing of a neuron.
More than 35 years ago I decided to become a neurologist, a specialist in brain disorders. And I have to admit that in the early years of my practice, I was hugely frustrated. I pretty much practiced under the idea of diagnose and adios. In other words, I would spend time making a proper diagnosis, but once that happened, there was often little I could offer my patients. In fact, throughout much of my career, I’ve had to tell patients and their caregivers that I have nothing to treat, let alone cure, a grave neurological disease that will inevitably shatter an otherwise vibrant life. It’s a heart-wrenching place to be, one that you just don’t get used to no matter how many times you go through it. What gives me hope, however, is this burgeoning area of study on the microbiome that I believe will result in revolutionary approaches to relieving the suffering.
Past and Present
We’ve made huge strides in the past century lowering the death rates of many life-threatening maladies, including infectious diseases, some forms of cancer and heart disease. But when you consider brain-related afflictions, the picture is vastly different. Let’s consider a few numbers.
In the ten wealthiest Western nations, death from brain disease in general, which largely reflects death from dementia, has risen dramatically over the past 20 years. And the United States leads the way. In fact, a 2013 British report showed that since 1979, death due to brain disease increased a breathtaking 66 percent in men and 92 percent in women in America. This surge, which is affecting people at younger and younger ages, is in sharp contrast to the major reductions in risk of death from all other causes.
In 2013, the prestigious New England Journal of Medicine published a report revealing that we spend about $50,000 annually caring for each dementia patient in this country. That amounts to approximately $200 billion a year, twice what we spend on caring for heart disease patients and almost triple what we spend on treatment for cancer patients. Over the next 40 years, the total cost of care for these patients is expected to exceed $20 trillion.
Mood and anxiety disorders are also increasingly diagnosed. About one in four adults in the U.S.—more than 26 percent of the population—suffers from a mental disorder. Anxiety disorders afflict more than 40 million Americans, and nearly 10 percent of the U.S. adult population has a mood disorder for which powerful drugs are prescribed. Depression, which affects one in 10 of us, including a quarter of women in their 40s and 50s, is now the leading cause of disability worldwide.
Headaches, including migraines, are among the most common disorders of the nervous system. Nearly half of the adult population wrestles with at
least one headache per month. And they are more than an inconvenience; they are associated with disability, personal suffering, damaged quality of life and financial cost. Multiple sclerosis, a disabling autoimmune disease that disrupts the nervous system’s ability to communicate, now affects an estimated two and a half million people worldwide, with close to half a million in America, and is becoming increasingly more prevalent. The average lifetime cost of treating someone with MS exceeds $1.2 million.
And then there is autism, which has surged seven-to-eight-fold just in the past 15 years, making this truly a modern day epidemic. Billions of dollars are being spent on these and other enfeebling brain-related ailments, yet we are seeing precious little progress. Now for the good news: stunning new science coming from the most well respected institutions around the world is discovering that, to an extraordinary degree, brain health is inextricably linked to the organisms that populate and live in the gut.
Unfortunately, most of today’s neurologists were trained to focus on what goes on in the nervous system, and specifically in the brain, in a myopic way. The entire medical industry is characterized by distinct disciplines divided by body part or individual system. But this perspective is grossly out of touch with current science. In my education, I wasn’t satisfied with this highly narrow-minded view of the body being just a bunch of separate parts and systems. Years ago, I began studying nutrition and ultimately became a fellow of the American College of Nutrition. This has served me well in light of our new understanding that, in fact, the digestive system is intimately connected to the nervous system. These two systems in no way stand apart. And perhaps the most important aspect of the gut that has everything to do with your general wellness is its internal ecology—the various microorganisms that live within it that comprise your microbiome.
Meet Your Microbiome
Historically, we’ve learned to think of bacteria as agents of death. The bubonic plague, after all, wiped out nearly one third of the population in Europe between 1347 and 1352, and certain bacterial infections are still worldwide killers today. But the time has come to embrace another side of bacteria’s story in our lives.
We must consider how some of these microscopic bugs are not detrimental but fundamental to life. The Greek physician and father of modern medicine, Hippocrates, first said in the third century B.C.E., “All disease begins in the gut.” This was long before civilization had any proof or sound theory to explain this idea. We didn’t even know bacteria existed until the Dutch tradesman and scientist Antonie van Leeuwenhoek looked at his own dental plaque through a handcrafted microscope in the late 17th century and spied a hidden world of what he called “animalcules.” Today, he is considered the father of microbiology.
Right now, your body is colonized by a multitude of organisms that outnumber your own cells by a factor of about ten. (Luckily, our cells are much larger, so those organisms don’t outweigh us ten to one!) These roughly hundred trillion invisible creatures—microbes—cover your insides and outsides, thriving in your mouth, nose, ears, intestines, genitalia and on every inch of your skin. If you could isolate them all, they would fill up a half-gallon container.
Scientists have so far identified some 10,000 species of microbes, and because each microbe contains its own DNA, that translates to more than eight million genes. Think of it: fully 99 percent of the genetic material in your body is found not in your genes, but in the genes of the bacteria living on and inside you!
Most of these organisms live within your digestive tract, and while they include fungi and viruses, it’s the bacteria that take center stage in supporting every conceivable aspect of your health. And you interact not only with these organisms but also with their genetic material. What’s even more amazing is that these microbes not only influence the expression of our DNA but new research also reveals that, throughout our evolution, microbial DNA has become part of our own DNA. In other words, genes from microbes have inserted themselves into our genetic code to help us evolve and flourish.
These new discoveries have lit a fire under me. Understanding the human microbiome offers the promise that change is possible. So, you likely understand why I’m so excited. And honoring the optimal health of your microbiome is easier than you think.
Although the human genome we all carry is almost the same, give or take the relatively small handful of genes that encode our individual characteristics such as hair color or blood type, the microbiome of even identical twins is not the same. Scientific research is now acknowledging
that the state of the microbiome is so key to human health—with a sweeping say in whether or not we live robustly to a ripe old age—that it should be considered an organ in and of itself. And it’s an organ that has gone through radical changes over the past two million years. We have evolved to have an intimate, symbiotic relationship with these microbial inhabitants who have actively participated in shaping our survival since the dawn of humankind. (And, indeed, they lived on the planet for billions of years prior to our emergence.) At the same time, they have adapted and changed in response to the environments we have created for them within our bodies.
The importance of the microbiome motivated the National Institutes of Health (NIH) to launch the Human Microbiome Project in 2008 as an extension of the Human Genome Project. Some of America’s best scientists have been charged with exploring how changes in the microbiome are associated with health. Moreover, they are studying what can be done with this information to help reverse many of our most challenging health problems. Although the project is investigating several parts of the body that host microbes, including the skin, the most extensive area of research is focused on the gut, since it’s home to most of your body’s microbes and, as you’re about to discover, a center of gravity of sorts for your entire physiology.
Just What Do These Gut Bugs Do For Us?
The latest science tells us that the intestinal flora that take up residence on the delicate folds of your intestinal walls:
• aid in digestion and the absorption of nutrients.
• support immune system function and cleansing functions within the body.
• produce and release important enzymes and substances that collaborate with your biology as well as chemicals for the brain, including vitamins and neurotransmitters.
• help you handle stress through the flora’s effects on your endocrine—hormonal—system.
• assist you in getting a good night’s sleep.
Put simply, our microbiome influences practically everything about our health, including how we feel both emotionally and physically.
The Ultimate Brain Maker
Think of the last time you felt sick to your stomach because you were nervous, anxious, scared or perhaps over-the-moon elated. Maybe it was before taking an important test, speaking before a group of people or getting married. Scientists are just learning that the intimate relationship between your gut and brain is actually bidirectional: just as your brain can send butterflies to your stomach, your gut can relay its state of calm or alarm to the nervous system.
This two-way highway is made possible by the vagus nerve, the longest of the twelve cranial nerves. It’s the primary channel of information between the hundreds of millions of nerve cells in your intestinal nervous system and your central nervous system. Also known as cranial nerve X, it extends from the brain stem to the abdomen, directing many bodily processes that we don’t consciously control. These include such important tasks as maintaining the heart rate and controlling digestion. And it turns out that the population of bacteria in the gut directly affects the stimulation and function of the cells along the vagus nerve. Some of the gut’s microbes can actually release chemical messengers, just as our neurons do, that speak to the brain in their own language through the vagus nerve.
When you picture your nervous system, you probably think of your brain and spinal cord. But that’s just the central nervous system. You must also consider your intestinal or enteric nervous system, the one that’s intrinsic to the gastrointestinal tract. The central and enteric nervous systems are created from the same tissue during fetal development, and they are connected via the vagus nerve. Vagus means “wanderer,” an apt name for this nerve, which wanders through the digestive system. (The word vagabond comes from the same root.)
The neurons in the gut are so innumerable that many scientists are now calling the totality of them “the second brain.” Not only is this second brain regulating muscles, immune cells and hormones, but it’s also manufacturing something really important: the “feel-good” chemical serotonin. An estimated 80 to 90 percent of the amount of serotonin in your body is actually manufactured by the nerve cells in your gut! The fact that our enteric nervous system can act independently from the main brain and control many functions without the brain’s input or help is why some researchers assert that our second brain may not be “second” at all.
Your gut also has its own immune system that represents 70 to 80 percent of your body’s total immune system. This speaks volumes about the importance of your gut.
Each large group of gut bacteria has many different strains, and each of these strains may have different effects. The two most common groups of organisms in the gut, representing more than 90 percent of the bacterial population in the colon, are Firmicutes (pronounced fir-MIH-cue-tees) and Bacteroidetes (pronounced BAC-teer-OY-deh-tees). Firmicutes are notorious as “fat-loving” bacteria, for it’s been shown that the bacteria in the Firmicutes family are equipped with more enzymes to digest complex carbohydrates, so they are much more efficient at extracting energy (i.e., calories) from food. They also were just recently found to be instrumental in increasing fat absorption. Researchers have discovered that obese people have elevated levels of Firmicutes in their gut flora, compared to lean people, who are dominated more by Bacteroidetes. In fact, the latest research shows that the relative proportion of these two groups to each other, the Firmicutesto-Bacteroidetes (or F/B) ratio, is critical for determining health.
While it’s thought that each of us was once germ free when we were in our mother’s womb, a relatively sterile environment, I expect this notion to be challenged very soon. New science is just emerging that suggests the fetus may be exposed to microbes in utero through the placenta, and that the microbiome actually begins there. But the current thinking is that the moment we move through the birth canal and are exposed to organisms in the vagina, our microbiome begins to develop. And while you may not want to picture this in your mind, even a mother’s fecal material in the perianal area helps to inoculate the newborn with health-sustaining microorganisms.
Although you can’t change what kind of microbiome developed in (and on) you as an infant, the good news is that you still have the power to support and nourish a healthy microbiome through what you eat, what you’re exposed to in the environment and what kind of lifestyle you lead. Let’s briefly run through the three biggest forces that work against the health of your gut’s good bugs.
• Force #1: Exposure to substances that kill or otherwise adversely change the composition of the bacterial colonies. These include everything from
environmental chemicals to certain ingredients in food (e.g., sugar, gluten), water (e.g., chlorine) and drugs such as antibiotics.
• Force #2: Lack of nutrients that support healthy, diverse tribes of bacteria.
• Force: #3: Stress. While it may sound like a cliché to say that stress is bad for your health, it’s even worse than we previously thought due to its
detrimental impact on the microbiome.
Clearly, some of these are impossible to avoid at all times. There will be situations, for example, when antibiotics are lifesaving and necessary. But the biggest takeaway of all is that what you eat is arguably the most significant factor related to the health and diversity of the microbiome. In fact, in my opinion, a key reason why we haven’t been able to make progress is because we’ve been traumatizing our microbiome through our modern diet that’s high in sugar and manufactured fats. And some of the foods that you may think are healthy are actually assaulting your good gut bacteria—things such as wheat products and diet sodas.
I mention diet sodas in particular because millions of people think they’re making a better choice to drink artificially sweetened beverages over regular soda. But research has just demonstrated, to the surprise of many scientists, that artificial sweeteners do a number on our gut bacteria.
Artificial sweeteners not only change the composition of the gut bacteria, but they also favor the overgrowth of species that increase the risk of metabolic conditions such as diabetes and obesity even more than sugar-sweetened beverages do.
The inescapable truth is that we have co-evolved with these microorganisms throughout our journey on this planet. They are the body’s—and brain’s—best friends. And they are as much a part of our survival as our own cells are. Unfortunately, many of us are mistreating our intestinal flora and subjecting them to hazardous conditions.
It’s time to take care of them as they deserve. Only then will we be able to make serious, meaningful headway against many of our modern afflictions and live a long, mentally vigorous life. Adapted from Brain Maker (Little, Brown 2015).