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Food & Mood
The Complete Guide to Eating Well and Feeling Your Best
By Elizabeth Somer
Henry Holt and CompanyCopyright © 1999 Elizabeth Somer
All rights reserved.
How Food Affects Your Mood
What a miracle you are!
With little or no effort, you can remember simple and complicated facts and events, so that by the time you have reached adulthood, you are a rich canvas of experiences, memories, and relationships.
You can feel a wide array of emotions, from ecstasy and grief to boredom and apathy.
You can solve problems, untangle puzzles, develop plans, and form opinions.
You have a unique sense of humor and a one-of-a-kind personality, as well as personal dreams and hopes for the future.
You are unique in the foods you love, the foods you hate, the foods you crave, and the foods you eat daily. Even how you decide what food satisfies a craving and how you go about soothing that need is peculiar just to you.
At the very foundation of each of these traits, talents, and preferences is an orchestra of cells and chemicals that allow your basic nature to develop and interact with the world. Who you are depends on how well that orchestra, called your nervous system, plays its music.
Getting to Know Your Neurons
The smallest functioning unit of the nervous system is the nerve cell, or neuron. This cell "talks" to other nerve cells and tissues by relaying electrical messages within the brain and back and forth through the nervous system to the rest of the body. To instinctively pull your hand away from a hot burner on the stove, blink an eye, feel hunger, decide what to eat, prepare a meal, hear a noise and recognize its origin, memorize a song, smell cinnamon and know it's coming from the bakery down the street, or perform any of the millions of thoughts, feelings, and actions you do every day requires that thousands of your 100 billion nerve cells and an equivalent number of support cells (called glia) communicate efficiently.
The neuron is not your typical cell. Most cells in the body are relatively spherical, but the nerve cell is shaped more like a tree. On one end are its branches, called dendrites, which allow the nerve cell to receive incoming messages from other neurons. These messages are relayed down the "trunk" of the nerve cell (called the axon), much like voice messages are carried on telephone wires. The axon can vary in length, from a fraction of a millimeter to three feet long (see Illustration 1.1). The messages eventually reach the "roots," or axon terminals, of the nerve cell, which bump against dendrites on other nerve cells. Nerve cells don't touch. Instead they are separated by tiny spaces that flow between the axon terminal of the sending nerve cell and the dendrites of the receiving nerve cell. This tiny space is called the synapse.
In order to relay the message from one nerve cell to the next, the sending nerve cell must find a way to "jump" the gap, or synapse, to get to the other side. Without some way to transmit messages across this gap, messages would stop at the end of the sending nerve cell, and all processes dependent on the nervous system, from moods to movements, would come to a halt.
To ensure this does not happen, nerve chemicals called neurotransmitters are stored in tiny sacs at the end of the axon terminals. The electrical message (such as a thought or a feeling message) traveling down the axon arrives at the terminal and causes some of these sacs to release their neurotransmitters. These nerve chemicals flow across the synapse, tickle the receiving nerve cell, and keep the message moving from one nerve to another, much like handing the baton to the next runner in a relay race. Once the neurotransmitter has relayed its message, it is broken down or reabsorbed back into the receiving nerve cell's storage space to be used again. In this way, neurons communicate with each other and send "state-of-the-union" messages from the body to the brain, and back again. The brain processes this information by sending messages back and forth among its billions of nerve cells and then releasing orders for action to the muscles and organs of the body — all within a split second and with no conscious effort on your part. Every dip or rise in mood, every hunger pang, every thought, every response — in short, who you are — is orchestrated by these nerve cells and their neurotransmitters.
A Symphony of Chemicals
Until recently, scientists had identified only a few chemicals and hormones that regulated body and brain processes, including insulin, adrenalin, noradrenaline, and glucagon. But in the past twenty-five years the chemical story has become considerably more complex with hundreds of newly identified compounds that regulate everything from your mood and what you want to eat to whether or not you experience headaches or develop heart disease.
The participants in this chemical symphony include neuropeptides such as neuropeptide Y (NPY) and galanin; amines; prostaglandins such as the prostacyclines and thromboxanes; the leukotrienes; and numerous hormones, from cholecystokinin (CCK), estrogen, and testosterone to cortisol, prolactin, and adrenocorticotropic hormone (ACTH). It is likely these and many other chemicals we've discovered recently are just the beginning and that many more compounds will be identified in the future.
At least seventy neurotransmitters have been identified that regulate nerve function, including memory, appetite, mental function, mood, movement, and the wake-sleep cycle. Table 1.1, "Some of the Chemicals That Influence When and What You Eat," provides a partial list of these neurotransmitters and other hormonelike compounds along with their effects on appetite. Disruption of even one neurotransmitter dramatically alters nerve cell function and instigates a cascade effect on other neurotransmitters, which can have profound effects on one or more of our physical, emotional, and mental processes. In essence, if an electrical message comes down the axon but there are insufficient amounts of the correct neurotransmitter at the terminal, then the message is not communicated to the next neuron, and the information flow stops. For example, too little of the neurotransmitter acetylcholine results in memory loss, while too little of the neurotransmitter norepinephrine causes depression. Too much of other neurotransmitters can over-communicate a message. For example, excessive amounts of norepinephrine causes the mental disorder called mania.
To further complicate the symphony, these neurotransmitters are housed in central regions of the brain — such as the hypothalamus — that also regulate reproduction and communicate closely with other brain centers — such as the amygdala — that control emotions. Our food preferences, desires, cravings, and loves are literally hardwired into our basic instincts for survival, safety, and love!
What You Eat Affects How You Feel
What you eat directly and indirectly affects all these nerve chemicals, which in turn influence your moods, energy level, food cravings, stress levels, and sleep habits. For example:
1. Many neurotransmitters are composed of either amino acids — the building blocks of protein obtained from the diet — or a fatlike substance called choline, also obtained from food. When you consume too little of one or more of these dietary building blocks, your body limits production of the neurotransmitter dependent on their availability, and you experience changes in mood, appetite, and thinking. For example, the nerve chemical histamine is built from the amino acid histadine. Histamine is important in regulating alertness; brain energy metabolism; the release of hormones; appetite; and coordination.
2. Vitamins or minerals, such as the B vitamins, vitamin C, vitamin E, iron, selenium, and magnesium, are assembly-line workers in the manufacture of neurotransmitters; some aid neurotransmitter activity, as in the case of iron, and some protect neurotransmitters from damage, as in the case of vitamin E. If your diet does not supply ample amounts of these "helpers," neurotransmitters are not made or stored in sufficient amounts, and you feel grumpy or can't think straight. Correct these deficiencies, and mood and thinking improve.
3. Some neurotransmitters become more or less active depending on dietary intake. Either overconsuming or dramatically restricting a particular food, such as fats or carbohydrates, can trigger imbalances in neurotransmitters that can contribute to depression, irritability, food cravings, mood swings, and thinking problems (see Illustration 1.2, above).
4. Nutrients such as protein, zinc, vitamin B, iodine, folic acid, and vitamin B are essential for the normal development of the nervous system. Insufficient intake of these nutrients from conception through the early years of life results in potentially irreversible damage to the nervous system, thus permanently altering personality, mental function, and behavior.
5. Some food additives, such as monosodium glutamate (MSG), and chemicals, such as tyramine (found in aged cheeses), can influence brain activity and result in mood changes, or can interfere with the manufacture or release of neurotransmitters. Other additives can block neurotransmitters so the receiving neuron is unable to understand the message. Still other additives alter the structure of a neurotransmitter, increase your cells' output of neurotransmitters, or affect the enzymes that normally regulate how much neurotransmitter remains in the gap between nerve cells. Any of these changes can have profound, yet sometimes subtle, effects on your mood and thinking.
The Diet-Made Chemicals: Serotonin, Dopamine, Norepinephrine, and Acetylcholine
The manufacture of most neurotransmitters is controlled by the brain. But some are directly influenced by what you eat, especially the amino acids (the building blocks for protein). For example, there are five neurotransmitters whose origins can be directly linked to the food we eat. Tryptophan, an amino acid found in meat and milk, is the building block for serotonin, and dopamine and norepinephrine are influenced by the amount of tyrosine in the diet. Histadine intake helps regulate production of histamine, and threonine is the building block for a nerve chemical called glycine. Some fatlike compounds also turn on production of nerve chemicals. For example, eating choline-rich foods boosts acetylcholine production. The levels and activity of these neurotransmitters are sensitive to food intake, and changes in dietary patterns can have profound effects.
Serotonin: General Mood Regulator
The neurotransmitter serotonin performs a variety of functions. High serotonin levels boost your mood, curb your food cravings, increase your pain tolerance, and help you sleep like a baby. Low levels of serotonin result in insomnia, depression, food cravings, increased sensitivity to pain, aggressive behavior, and poor body temperature regulation.
No other neurotransmitter is as strongly linked to your diet as is serotonin. This neurotransmitter is manufactured in the brain from an amino acid called tryptophan, with the help of a variety of nutrients including vitamins B and B, and folic acid. As blood and brain levels of tryptophan rise and fall and as vitamin intake fluctuates between optimal and deficient, so follow serotonin levels. Serotonin levels rise twofold when people take tryptophan supplements, which reduce the time it takes for an insomniac to get to sleep; boost mood in people battling depression; calm people prone to violence; increase tolerance to pain; and help curb carbohydrate cravings. People who take medications — such as fenfluramine, for weight loss — that boost serotonin activity also report improvements in mood and a drop in calorie intake. This serotonin-stimulating drug also increases alertness and sociability and decreases feelings of tiredness and irritability. (A cousin to tryptophan available in supplements is 5-hydroxytryptophan [or 5-hydroxy-L-tryptophan (5-HTP)], which improves mood in some people, but whether it is safe or effective for other symptoms of serotonin deficit is unknown.)
Ironically, eating a protein-rich meal lowers brain tryptophan and serotonin levels, and eating a carbohydrate-rich snack has the opposite effects. Tryptophan is a large amino acid that shares an entry gate into the brain with several other large amino acids, such as tyrosine. When you eat a protein-rich meal, you flood the blood with both tryptophan and its "competing" amino acids, and they fight for entry into the brain. Tryptophan gets crowded out, and only a small amount gets through the blood-brain barrier (the series of membranes, enzymes, and blood vessels that separate the brain from the body and, as a whole, act as the gatekeeper protecting the brain from harmful substances, such as some drugs, radioactive compounds, and disease-causing viruses). (See Illustration 1.2.) As a result, serotonin levels do not rise appreciably after a meal or snack that contains protein, even if that food is high in tryptophan.
In contrast, a carbohydrate-rich meal triggers the release of insulin from the pancreas. This hormone causes most amino acids floating in the blood to be absorbed into the body's (not the brain's) cells — all, that is, except tryptophan, which remains in the bloodstream at relatively high levels. With the competition removed, tryptophan can freely enter the brain, causing serotonin levels to rise. The high serotonin levels increase feelings of calmness or drowsiness, improve sleep patterns, increase pain tolerance, and reduce cravings for carbohydrate-rich foods. (See "Diet and Serotonin Levels".)
Dopamine and Norepinephrine: Mood and Energy Elevators
Dopamine and norepinephrine (also called noradrenaline) are manufactured from the amino acid tyrosine with the help of several other nutrients, including folic acid, magnesium, and vitamin B. When your dopamine and norepinephrine levels drop, you're more likely to feel depressed, irritable, and be moody; consuming more tyrosine boosts levels of these neurotransmitters and improves mood, alertness, ability to cope with stress, and mental functioning.
Like tryptophan, tyrosine is found in protein-rich foods. Unlike tryptophan, tyrosine levels in the blood and brain rise when a person consumes pure tyrosine or, to a lesser extent, eats a protein-rich meal. The same processes that lower tryptophan levels — that is, high levels of competing amino acids and no insulin — are the very processes that favor tyrosine. Consequently, tyrosine and tryptophan are at odds with one another: For tryptophan/serotonin levels to rise, tyrosine levels must be low; conversely, when tyrosine and its corresponding neurotransmitters are high, tryptophan levels are moderate to low.
This seesaw relationship between tyrosine and tryptophan results in a similar effect on appetite. Eat a carbohydrate-rich breakfast, such as pancakes or waffles, and serotonin levels rise, which will shut off the desire to eat more carbohydrates. At the next meal you'll be more likely to select a low-carbohydrate, high-protein selection, such as a tuna sandwich with milk, which raises dopamine/ norepinephrine levels. And so we swing back and forth from carbohydrates to proteins throughout the day, in part because of fluctuations in these neurotransmitters. To examine your own mood swings and energy levels, try Quiz 1.1, "What You Eat and How You Feel".
Raising blood levels of tryptophan always increases the manufacture of serotonin in the brain, but raising blood levels of tyrosine increases dopamine and norepinephrine levels only if:
1. The nerve cells are using these neurotransmitters and need more; or
2. Nerve cell numbers are reduced, as in aging.
In the second case, fewer cells are working harder (that is, sending more messages and needing more neurotransmitters) in an attempt to compensate for the dwindling numbers of cells. Tyrosine supplements boost dopamine levels in Parkinson's disease patients with degeneration of the nerves that produce dopamine.
A building block for tyrosine, the amino acid phenylalanine, is found in the brain in small amounts. Although its structure resembles that of amphetamines, it is unknown whether phenylalanine can affect behavior or curb appetite. However, a few studies show that this amino acid might help curb depression and improve symptoms of attention deficit disorder in adults.
Acetylcholine: The Memory Manager
When it comes to choline, the food-and-mood link is straightforward. Unlike amino acids, which must compete for entry into the brain, the fatlike substance choline has no competitors. The more you consume, the more it makes its way into the brain, where it is converted to a neurotransmitter called acetylcholine. This nerve chemical is important in memory and general mental functioning; dwindling acetylcholine levels, which are common with aging, result in memory loss and reduced thinking ability. Choline also might be effective in the treatment of tardive dyskinesia (a nerve disorder characterized by uncontrollable movements), mania, and possibly Alzheimer's disease. You can boost brain levels of choline by consuming choline-rich foods such as wheat germ and eggs, taking lecithin or choline supplements, and/or taking nicotinamide (a form of the B vitamin niacin), which enhances brain concentrations of choline.
Excerpted from Food & Mood by Elizabeth Somer. Copyright © 1999 Elizabeth Somer. Excerpted by permission of Henry Holt and Company.
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