The Serotonin Story

Most people have a rather vague idea what serotonin is...some brain chemical that is connected to a person’s feeling of well-being. They might also know that serotonin levels are modified by the foods we eat and the drugs we take. Beyond that, most people don’t know a lot.

If you read my previous blog entry, you’ll have an idea how the belief that low levels of serotonin cause depression developed, how this belief enabled some  clever marketing gurus to generate a multi-billion dollar antidepressant industry, and why this myth continues to linger in the public psyche.

This blog entry looks at the history of the discovery of serotonin, and what it REALLY does.

Serotonin was first discovered by an Italian researcher, Vittorio Erspamer, in the 1930s while studying the gastric and sexual function of rats and rabbits, and later dogs, molluscs and octopi. He called the substance enteramine, and noted that it affected intestinal and uterine muscle movement and contractions. In the late 1940s in the U.S., a substance was identified as a blood component responsible for vasoconstriction; researchers there named it serotonin (sero-serum, tonin-tonic or toner). It wasn’t until the early 1950s that scientists tweaked to the idea that enteramine and serotonin were the same substance, and it was 1953 before it was realized, by American researcher Betty Twarg, that in addition to its hormonal function, serotonin also operated in the brain as a neurotransmitter.

A hormone is a substance produced by the body that regulates bodily functions. As a hormone, serotonin helps to regulate the digestive tract, the central nervous system, and the formation and flow or clotting of blood platelets. Approximately 80%-90% of the body’s serotonin can be found in the gut where it regulates intestinal movement. As a neurotransmitter—a chemical that transfers information from one nerve cell to another—serotonin also moderates and affects a person’s moods, sleep, memory, and learning.

The precursor to serotonin, tryptophan, is an essential amino acid derived from one’s diet. Many protein-based foods are high in tryptophan including fish, meat, poultry, dairy products, eggs, beans, peas, seeds, spirulina, oats, and dark chocolate. However, these foods are also precursors for several other (competing, if you will) amino acids. The addition of high carbohydrate foods such as whole grain breads and pasta, and fruits such as bananas, dates and tomatoes can increase the conversion of tryptophan to serotonin over some of the other amino acids, increasing the feel-good result.

Low levels of serotonin in the body may result in fatigue, impaired cognitive function, insomnia, anxiety, and/or depression. On the other hand, unnaturally high levels of serotonin (usually as a result of supplements or drugs, prescribed or otherwise, or withdrawal of drugs that affect the serotonergic system such as antidepressants or lithium) can result in what’s known as serotonin syndrome with symptoms that include agitation, nausea, vomiting, diarrhoea, increased heartbeat, tremors or muscle spasms, mental confusion, and/or hallucinations. Severe untreated serotonin syndrome can result in death.

As with many things, moderation seems to be the key to keeping serotonin levels balanced and functioning properly in the body and brain. Eating a well-balanced diet should provide all of the tryptophan and triggers your body needs to manufacture appropriate levels of serotonin. Regular exercise and mood-modifying practices such as meditation also encourage the body to maintain a healthy level of serotonin.

One final idea: there is a school of thought that suggests increased levels of serotonin may come from feeling good rather than the other way around. It’s the old chicken and egg argument: which came first? It seems to me that it doesn’t really matter—one is bodily material, the other is mental/emotional-ethereal. It does us well to take care of our personal well-being on both the physical and the mental/emotional level. It also does us well to remember that serotonin is just one of the many natural substances that help our bodies and minds to function properly, and that deliberately throwing one out of balance (e.g., as with taking prescribed antidepressants that affect one or more neurotransmitters—be it serotonin, dopamine, norepinephrine) will undoubtedly affect the functioning of everything else in the body.

For more information on the role of serotonin and other neurotransmitters, and the drugs developed to "control" them, see my new book Reframing Mental Illness.