In upcoming chapters, we’re going to be exploring all of these connections—the indelible links between your gut and its microbial inhabitants, your immune system, and the orchestra of hormones that course through your body in sync with a day-night cycle. These connections influence the state of your entire physiology and, as important, your mental health and overall sense of well-being. While it may seem odd to talk about the gut-based immune system in terms of mental health, the latest science reveals that it may be the body’s—and mind’s—center of gravity. Just as I write this, yet another new study has emerged that overturns decades of textbook teaching about the brain and immune system. Researchers at the University of Virginia School of Medicine have determined that the brain is directly connected to the immune system by lymphatic vessels we didn’t know existed.25 That we had no idea about these vessels given the fact that the lymphatic system has been so thoroughly studied and charted throughout the body is astonishing on its own. And such a discovery will have significant effects on the study and treatment of neurological diseases, from autism and multiple sclerosis to Alzheimer’s disease and, yes, depression. It’s time we rewrite the textbooks. And it’s time we treat depression for what it really is.
So if depression isn’t a disease, then what is it? As I briefly mentioned in the introduction, depression is a symptom, a vague surface sign at best that doesn’t tell you anything about its root cause. Consider, for a moment, that your toe hurts. Any number of things can cause a toe to hurt, from physically injuring it to a bunion, blister, or tumor growing inside. The hurting is a sign that something is wrong with the toe, simple as that. Likewise, depression is the hurting; it’s an adaptive response, intelligently communicated by the body, to something not being right within, often because things are also off in our environment.
Depression doesn’t always manifest with feelings of serious melancholy and sadness or the urge to sit on the couch all day brooding. I can’t even remember the last patient I saw who was like the person you see on a TV commercial for an antidepressant. All of my patients experience anxiety—an inner kinetic discomfort, restlessness, unease, and a lot of insomnia. In fact, most cases of depression involve women who are very much on the go and productive, but they are also anxious, scatterbrained, overly stressed out, irritable, forgetful, worrywarts, unable to concentrate, and feeling “wired and tired” at the same time. And many of them have been dismissed by the medical system; their psychiatric problems were created by mistreatment as they fell into the vortex of endless prescription medications.
Take, for another example, a forty-two-year-old patient of mine we’ll call Jane, who fell into this black hole after being treated for irritable bowel and acne with drugs, including the now discontinued Accutane (isotretinoin). Jane experienced a depressed mood, a common side effect of Accutane, and was then put on an antidepressant as she stopped the medication (isotretinoin is a retinoid, a strong medication used to treat severe acne; it causes birth defects in babies born from mothers who take it during pregnancy, so it’s carefully regulated and only available in its generic form under a special program). After the death of her parents, which triggered more symptoms of depression, Jane was diagnosed with a thyroid problem, and her doctor at the time prescribed radioablation therapy, which destroys thyroid tissue with radioactive iodine 131. This led to her having acute panic attacks, and she soon began taking Xanax. Symptoms of more thyroid problems, including brain fog, extreme fatigue, and physical pain, culminated in a diagnosis of fibromyalgia. Jane was then treated with birth control pills and an antibiotic and soon developed chronic yeast infections, bloating, and abdominal pain. By the time she came to me, Jane had a twenty-four-hour home health aide.
Jane’s experience reflects that of so many people labeled as depressed and sent away with yet another prescription. The system creates patients who are otherwise healthy and just need to recalibrate their bodies using simple lifestyle interventions, mostly around diet—not drugs. After all, it is through diet that we communicate with our environment. It’s a dialect that we’ve forgotten how to speak.
AN EVOLUTIONARY MISMATCH
Take a look around you and appreciate the world we live in today with its technologies and conveniences: computers, cars, cell phones, and supermarkets. But also consider the mismatch between this scenario and the days when we had to forage for our food and sleep under the stars. Our caveman days are still very much a part of our DNA because evolution is slow; what seems like ages in cultural time (20,000 years ago) is but a blink of an eye in biological time. Which brings me to ask the question: Is all this depression simply a sign of an evolutionary mismatch?
This is the term that encompasses the source of most modern ills. We are engaged in lifestyles that are not compatible with what our genome has evolved over millions of years to expect. We eat a poor diet, harbor too much stress, lack sufficient physical movement, deprive ourselves of natural sunlight, expose ourselves to environmental toxicants, and take too many pharmaceuticals. Our wayward departure is marked by two specific revolutions in the history of mankind: the Neolithic, or agricultural, Revolution and the Industrial Revolution. For 99 percent of our existence, we followed the so-called Paleolithic diet, which is devoid of inflammatory and “insulinotropic” foods like sugar, grains, and dairy. Our body’s microbial ecology has been one of the primary victims of this shift—the 90 percent of our cells that are non-human in nature and that account for the majority of our body’s activities, which in turn impact the expression of our genes. I’ll be going into greater depth about the human microbiome in Chapter 3, but I’ll give you a short primer here because this discussion is important and will be carried throughout the book.
Although we’ve learned to think of bacteria as agents of death for the most part because certain strains can cause lethal infections in compromised hosts, new science is compelling us to consider how some of these microscopic bugs are fundamental to life—and mental health. As you read this, some 100 trillion microbes are colonized in your intestines alone.26 They outnumber your own cells by a factor of about ten, covering your insides and outsides. And they contain estimates of more than 8 million genes of their own, which means that fully 99 percent of the genetic material in your body is not your own. It belongs to your microbial comrades. These microbes not only influence the expression of our DNA, but research 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 (mitochondrial DNA being the prime example) to help us evolve and flourish.
A great many of these invisible creatures live within your digestive tract, and while they include fungi, parasites, and viruses, it’s the bacteria that appear to hold the proverbial keys to the kingdom of your biology, as they support every conceivable feature of your health. In the future we’ll likely see how the other microbes contribute at least as much to our health as bacteria do. The microbiome is so crucial to human health that it could be considered an organ in and of itself. In fact, it has been suggested that since without it we could not live, we should consider ourselves a “meta-organism,” inseparable from it. This inner ecology helps you digest food and absorb nutrients, supports the immune system and the body’s detoxification pathways, produces and releases important enzymes and substances that collaborate with your biology (including chemicals for the brain, such as vitamins and neurotransmitters), helps you handle stress through its effects on your endocrine—hormonal—system, and even ensures you get a good night’s sleep. Put simply, your microbiome influences practically everything about your health, including how you feel both emotionally, physically, and mentally.
What compromises a healthy microbiome? Not surprisingly, your microbiome is vulnerable to three antagonizing forces: exposure to substances that kill or otherwise negatively change the composition of the bacterial colonies (these substances include everything from environmental chemicals and drugs like antibiotics to ingredients such as artificial sugars and processed gluten-containing foods); a lack of nutrients that support healthy, diverse tribes of good microbes; and unrelenting stress.
I’ve devoted an entire section to the amazing features of the microbiome, so you’ll gain plenty of knowledge about how it plays a role in your physical and mental well-being and how you can maintain an optimal colony of tribes. We have coevolved with these microorganisms