Various writers over the past century have compared the human brain to an elegant machine. Imagine that this machine is full of wires and that the wires are different-colored. Some are blue, some are red, some are green, and so on, but they all convey information from one part of the machine to another.
Now imagine that the blue wires are organized differently than the red wires, that the red wires are organized differently than the green wires, and so on. If you were to look inside your brain, you would discover that although its pathways are organized like the colored wires in your telephone or computer, it doesn’t actually use wires at all but instead uses cells, or neurons, to process information: One neuron is connected to the next and to the next, and so on. Indeed, this elegant machine, your brain, is composed of approximately 100 billion neurons, and within a single structure, the cortex, these neurons make an estimated 0.15 quadrillion connections with each other. These billions of neurons are not uniquely colored, but they do release unique chemicals, called neurotransmitters, onto each other.
What happens when molecules of a foreign substance—say, a drug or a morsel of food—interact with the neurons in this elegant machine? What happens to their neurotransmitters and,
as a result, to you?
The major point that I want to make in this book is that anything you consume—the drugs you take, the foods you eat—can affect how your neurons behave and, subsequently,
how you think and feel. In the course of illustrating this point, I examine what neuroscientists currently know about the actions of specific drugs and food in the brain and seek to advance your understanding of your own brain by demonstrating how its workings can be altered by what you “feed” it. Thus, I describe several neurotransmitter systems, including a little about their
basic role in the brain, and explore how various substances—be they plant extracts, nuts, mushrooms, spices, chocolate, or medicinal and recreational drugs—can influence these neurotransmitters in terms of their production, their release from the neuron, and their ultimate inactivation and excretion from the body. I also discuss the brain’s role in certain experiences—
for example, hallucinations, religiosity, pain, and the aging process—and the extent to which these experiences are influenced by what we consume. In addition, I consider the role of evolution in determining the brain’s responses to the food and drugs that we consume and place the use of some of these substances in cultural history.
A long time ago, our ancestors discovered that ingesting some plants or the body parts of certain animals produced effects that were rather unpleasant or even lethal.
Reference to these substances once appeared in a collection of prayers of comfort for the dying and referred to a type of spiritual medicine, at the time called a pharmacy, which was used principally to alleviate suffering near the end of life. Simply put, a pharmacy was a poison. Originally, the term pharmakos ( ϕαρ μ ακος ) referred to a human scapegoat, who was sacrificed, sometimes literally by poisoning, as a remedy for the illness of another person, usually someone far more important
in the local society. Later, around 600 BCE, the term came to refer to substances used to cure the sick. It is, of course, related to two terms now in use today: pharmacology, the scientific investigation into the mechanisms by which drugs affect the body, and psychopharmacology, the study of the effects of drugs upon the brain — effects that in turn are defined as “psychoactive.”
This book explores not only several drugs but also a range of foods with these effects. In fact, the single unifying property of these substances is that they are all psychoactive in some way;
they can affect your brain and therefore your behavior. By the end of the book, I hope that you will appreciate that the distinction between what is considered a drug (i.e., something that your brain wants or needs to function optimally) and food (i.e., something that your body wants or needs to function optimally) is becoming increasingly difficult to define. Indeed, the routine use of some substances, such as stimulants and depressants, is so universal that most of us do not even consider them to be drugs but, rather, actual food. Is coffee, tea, tobacco, alcohol, cocoa, or
marijuana a nutrient or a drug? For many people, the distinction has become rather blurred. I suggest that anything you take into your body should be considered a drug, whether it’s obviously
nutritious or not. As you will see, even molecules that are clearly nutritious, such as essential amino acids like lysine and tryptophan (which can be purchased in any grocery store today), exhibit properties that many of us would attribute to a drug.
REALLY BASIC NEUROSCIENCE AND PHARMACOLOGY
Just how food and drugs affect the brain is the focus of this book, and in subsequent chapters, we examine the details underlying the specific mechanisms involved in this process. But to the ground that discussion, we need first to consider some very basic anatomy and chemistry involving the brain and to generally define the key mechanisms involved in the brain–drug interactions.
Why are our brains located in our heads? Wouldn’t they be safer if they were deep in our chest, similar to the location of our hearts? Brains, regardless of how small or simple, have evolved at the best possible location to perform their principal function: survival of the individual and the species. With very few exceptions, brains are always located at the front end of an animal’s feeding “tube” or mechanism, which in humans and many other organisms is the tubular system (the alimentary canal) that extends from the mouth to the anus. Your brain makes it possible for you to find food by sight, sound, and smell and then to organize your behavior so that the front end of your feeding tube can get close enough to taste the food and check it for beneficial or potentially harmful contents before you ingest it. Once the food is in your feeding tube, it is absorbed and becomes available to the cells of your body. Your entire feeding tube and associated organs, also known as the gastrointestinal system, use nearly 70% of the energy you consume just to make the remaining 30% available to the rest of your body.
Your brain uses about 14% of the available consumed energy, and your other organs that allow you to reproduce and move around your environment (including your muscles and bones) utilize about
15 % . As you can see, very little energy is left over for other tasks in the body. These percentages give you some idea of the priorities — sex and mobility — that billions of years of evolution have set for your body to achieve.