Gary Wenk - Your Brain on Food: How Chemicals Control Your Thoughts and Feelings

Your Brain on Food

How Chemicals Control Your Thoughts and Feelings

Gary L. Wenk, PhD

Departments of Psychology and Neuroscience and Molecular Virology, Immunology and Medical Genetics The Ohio State University Columbus, OH

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Library of Congress Cataloging-in-Publication Data

Wenk, Gary Lee.

Your brain on food : how chemicals control your thoughts and feelings/

Gary L. Wenk.

p. ; cm.

ISBN 978-0-19-538854-1

1. Psychopharmacology. 2. Neuropsychology. 3. Neurochemistry. I. Title. [DNLM: 1. Brainphysiology. 2. Emotions. 3. Neurotransmitter

Agentsphysiology. WL 300 W475y 2010]

RM315.W46 2010

615.78dc22

2009047354

1 3 5 7 9 8 6 4 2

Printed in the United States of America on acid-free paper

for Jane

PREFACE

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 doesnt 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 substancesay, a drug or a morsel of foodinteract 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 consumethe drugs you take, the foods you eatcan 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 substancesbe they plant extracts, nuts, mushrooms, spices, chocolate, or medicinal and recreational drugscan 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 brains role in certain experiences for example, hallucinations, religiosity, pain, and the aging processand the extent to which these experiences are influenced by what we consume. In addition, I consider the role of evolution in determining the brains responses to the food and drugs that we consume and place the use of some of these substances in cultural history.

The brain contains over 100 known, or suspected, neurotransmitter chemicals and probably as many that have not yet been discovered. I have chosen to focus on those neurotransmitter systems most commonly associated with the psychoactive effects of drugs and nutrients that, in many cases, are regularly consumed today. In general, I discuss mostly brain stimulants in the first half of the book and mostly depressants in the second half, although, as you will see, this dividing line is far from hard and fast, mainly because the brain does not always behave in such a dichotomous manner. Therefore, some stimulants appear later in the book; some depressants appear earlier; and some substances that influence a given neurotransmitter discussed in one chapter turn up again as they relate to neurotransmitters discussed in other chapters. However, there is a constant across these chapters: Ive tried to organize much of the information about specific neurotransmitter systems according to the action of two types of substancesthose that mimic these systems, thereby acting as agonists, and those that block them, thereby acting as antagonists. These and other fundamental concepts in pharmacology, as well as information about the basic neuroscience of the brain, are further explained in Chapter 1. In contrast, I have deliberately paid little or no attention to substances that have psychoactive effects on the brain but whose mechanism(s) of action have not yet been adequately defined in the scientific literature, such as lithium. Furthermore, I have made no attempt to detail the many, still poorly understood, additional roles played by the neurotransmitters that I do discuss.

In essence, this book is intended not as an exhaustive review of all that is known about the topic of drugs and the brain but as a briefand, I hope, enjoyableintroduction to it. By the end of the book, you will know more than just how a select group of drugs or food works in your brain, you will be able to predict how substances that I did not discuss, and those that have not even been invented yet, might also affect your brain. Even better, you may look back on the chapters youve read and discover that they are much too simplistic for you now and that you want to learn more about greater complexities of brain function than this book covers. If reading this book motivates you to learn more about neuroscience and its associated topics, then I will have succeeded in my goal to advance your understanding of your brain. The suggested readings that Ive listed at the end of the book offer an excellent next step in that advancement.

This book could not have been written without the encouragement and generosity of my mentors, colleagues, family, and friendsparticularly David Olton, who patiently motivated my curiosity in the effects of drugs on the brain; James McGaugh, who inspired my interest in behavioral pharmacology; Giancarlo Pepeu, who has continued to nurture my interest in the role of drugs in the history of culture; Peabo Bryson, who challenged me to explore the role of neuroscience in religion; Paul Gold, for the many thought-provoking discussions on the Utah slopes; and Jacqueline Crawley, for her boundless enthusiasm and stimulating insights into the function of the brain. Their wisdom helped focus my fanciful ideas into rational theories. I will always be grateful to Catharine Carlin at Oxford University Press for her unflagging support and optimism at the beginning of this long journey. I also feel very privileged to have worked with Marion Osmun, my editor, who provided a nurturing combination of advice, encouragement, and bracing perspective. I am also grateful to the thousands of students who have taken my psychopharmacology classes and whose personal stories enliven these pages. Finally, for more than 30 years, I have been blessed to share my life with a woman of unrivaled intelligence and uncommon patience. Her profound personal wisdom has enriched my life in countless ways. This book is dedicated to Jane.