No one knows exactly how much of which dietary components are needed for optimal mental functioning. However, it has been established that nutrition plays a vital role in intellect, memory, thinking, and personality.


Most of the research linking nutrition with stress has focused on physical stress such as surgery, burns, or intense exercise. However, there is a growing body of literature that shows that emotional and mental stress not only alters hormone levels in a manner similar to physical stress, but further compromises optimal functioning by changing eating patterns, reducing nutrient absorption, increasing nutrient excretion, and altering the use of nutrients in stress related metabolic processes.


We know that within the brain, poor nutrition can limit blood circulation, which is important in supplying brain cells with the building blocks and oxygen they require for proper function.

Many studies now link depression to a lack of certain vitamins, especially the B vitamins which are used in nervous system function. Although vitamin B6 deficiency is rare in the United States, many people, especially women, do not get enough in their diets. A less than adequate intake may produce subtle changes in mood, even before a deficiency can develop.


The ingestion of different nutrients affect levels of chemicals in the brain called neurotransmitters. Neurotransmitters transmit impulses from one nerve cell to another, and they influence mood, sleep patterns, and thinking. Deficiencies (shortages) or excesses of certain vitamins or minerals can damage nerves in the brain, causing changes in memory, limiting problem-solving ability, and impair brain function. The four neurotransmitters that are manufactured directly from food components are serotonin, dopamine, norepinephrine, and acetylcholine.

1. Serotonin
Serotonin is a multi-functional neurotransmitter. Low serotonin levels cause insomnia, depression, food cravings, and increased sensitivity to pain. It can also cause aggressive behavior, and poor body-temperature regulation.

Serotonin is manufactured in the brain from amino acids (a building block of protein), called tryptophan, that affects the levels in the brain. As more tryptophan enters the brain, more serotonin is produced. Higher serotonin levels enhance mood and have a sedating effect, promoting sleepiness. This effect is partly responsible for the drowsiness some people experience after a large meal.

Eating a protein-rich meal decreases tryptophan which leads to low serotonin levels. Conversely, a carbohydrate-rich meal enhances the uptake of tryptophan by the brain by triggering a release of a hormone called insulin in the body. Insulin lets blood sugar into cells where it can be used for energy, but insulin also has other effects in the body. As insulin levels rise, more tryptophan enters the brain. In turn, tryptophan is converted to serotonin which produces a calming, drowsy effect.

2. Dopamine and 3. Norepinephrine (adrenaline)
Dopamine and norepinephrine (adrenaline) are manufactured from the amino acid tyrosine. Whatever the source of stress, physical or emotional, the body reacts by pumping out adrenaline, which triggers a cascade of other hormonal and nervous responses through the body preparing us to either fight or flee. Although the majority of today's stresses require no rapid physical action, our bodies still respond in this ancient and time honored way. Within less than a second of experiencing anxiety, the heart rate quickens, eyesight sharpens and blood is diverted to muscles and thickens in anticipation of repairing a wound received in battle.

Low levels of dopamine and norepinephrine are associated with depression, decreased ability to deal with stress, and a decline in mental functioning.

4. Acetylcholine
Choline, a fat like substance that is both produced by the body and found in food it is vital for the neurotransmitter acetylcholine. Acetylcholine is associated with memory and cognitive ability. A study at the University of Massachusetts showed that healthy people who took a drug that blocked acetylcholine flunked a memory test, but passed the test when they took a drug that increased acetylcholine levels. Other studies show that maintaining optimal choline levels may not only improve learning ability, but may slow certain forms of age-related memory loss.

Protein and Amino Acids

Proteins are made up of amino acids linked together in various sequences and amounts. The human body can manufacture some amino acids, but there are 8 essential amino acids that must be supplied by food. A complete or high-quality protein contains all 8 essential amino acids in the amounts needed by the body.

Foods rich in high-quality protein include meats, milk and other dairy products, and eggs. Dried beans and peas, grains, and nuts and seeds also contain protein, although the protein in these plant foods may be low in one or more essential amino acids. Generally, combining any two types of plant protein foods together will yield a complete, high-quality protein. For example, a peanut butter and jelly sandwich combines grain protein from the bread with nut protein from the peanut butter to yield a complete protein. A bean-rice hot dish combines bean and grain protein for another complete protein combination.

In summary, the neurotransmitters manufactured from the intake of protein and amino acids affect brain functioning and mental health. High levels of stress and poor eating patterns lead to nutritional deficiencies that may impact these neurotransmitter levels which in turn affect brain function.

In an ideal world, to break the cycle, you would decrease your level of stress. However, if this is not practical or probable, the next best solution is to arm yourself with a strong defense: a well nourished body and brain.

Nutrition and Diseases of the Nervous System 1999.
Nutrition in Clinical Practice. 2001.
Medical Nutrition Therapy for Neurologic Disorders 2000.

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About The Author

Michelle L. Taylor is the Wellness Program Director at Monarch Health Promotions in Tucson, Arizona

Please feel free to contact her on the web at or by phone at (520) 404-4558