Serotonin is a neurotransmitter or chemical carried between nerve cells that is responsible for a number of functions in the body. Serotonin has been dubbed the “feel-good” hormone in part because it appears to play a role in mood regulation, and specifically in elevating mood. But this chemical messenger plays a role in everything from digestion to sleep to bone health.
In theory, the concept of “boosting” serotonin might sound appealing, especially if it could help ward off bad moods. But is it really possible to increase serotonin and what effect would it have on the body? Live Science spoke to experts to find out.
What is serotonin?
Serotonin is a neurotransmitter, a type of natural chemical released by the brain and gut that enables communication between cells.
“Serotonin is synthesized using tryptophan, an amino acid that the human body does not produce and must be supplied through the diet,” said Dr. Teresa Poprawski. (opens in a new tab), a neuropsychiatrist and chief physician at Relief Mental Health in Illinois. “Although serotonin is often talked about in relation to the brain, almost all serotonin can be found in the cells lining the gut and in the blood.”
Only 1 to 2% of serotonin is found in the brain, although some sources report as much as 10%, Poprawski said.
Poprawski said that serotonin acts as a neurotransmitter in the brain and spinal cord and can act as a hormone in other tissues.
“Serotonin produced in the brain acts as a neurotransmitter, but serotonin produced in the gut acts as a hormone,” she told Live Science.
How does serotonin work?
Serotonin’s effects in the body depend on whether it acts as a neurotransmitter in the central nervous system (CNS), which consists of the brain and spinal cord, or as a hormone in other tissues.
Poprawski said that in the CNS, serotonin is secreted into the synaptic cleft, the space between two nerve cells, or neurons. One neuron releases serotonin and the other receives it.
“The neuron that secretes serotonin also controls the amount of serotonin in the synaptic cleft by reabsorbing the neurotransmitter, a process called reuptake,” she said. “Certain drugs can slow the rate of this reuptake and extend the effects of serotonin on the receiving neuron.” For example, selective serotonin reuptake inhibitors (SSRIs) are a type of antidepressant used to prolong the effects of serotonin on serotonin-responsive neurons, she said.
In addition to regulating mood, serotonin fine-tunes many CNS functions, including sleep, appetite, learning, memory and libido, Poprawski said.
Dr. Shaheen Lakhan (opens in a new tab), a neuroscientist based in Boston, Mass., said it has long been thought that fluctuating levels of serotonin can directly affect our mood. However, neurotransmitters are more complicated than we previously thought, and there is a much more dynamic interplay between these brain chemicals and various functions of our brain, including mood and behavior, he said.
“Just as advances in smartphones are really driven by the interplay of hardware and software, neural circuits that connect at least two areas of the brain are responsible for complicated functions such as mood, motivation, pleasure, cognition, memory and language,” he said. “In other words, there’s no single part of the brain or single neurotransmitter that exclusively drives these functions. It’s the hardware, the software, and the energy axis that make up the brain’s circuitry; and they’re not simply turned off or on, they’re modulated.”
Outside the CNS, serotonin not only regulates gut function, but also, when bound to platelets in the blood, regulates blood clotting and slows blood flow in the wound healing process, Poprawski said.
Serotonin is also synthesized into melatonin, both in the brain and in the gut, she added. Melatonin is the hormone primarily responsible for controlling our circadian rhythm, which relates to the body’s biological clock or natural sleep-wake cycle.
Do some people have more serotonin than others?
Like many neurotransmitters and hormones, some people produce more serotonin than others because serotonin synthesis depends on many factors that vary between individuals, Poprawski said. “Aspects like [blood levels] the amount of tryptophan and other large amino acids relative to tryptophan will largely depend on individual dietary habits,” she said.
Tryptophan hydroxylase is an enzyme that controls the rate of serotonin production. The activity of this enzyme, in turn, depends on gene expression, meaning which genes are “on” or “off,” which is highly variable and influenced by genetics and environmental factors, Poprawski said.
Is it possible to “enhance” serotonin production?
According to Poprawski, it is possible to increase serotonin production, but most people make enough of the chemical.
If the levels are low enough to require medical intervention, doctors will first need to find out why they have dropped.
Symptoms of low serotonin can include anxiety, depression, lack of concentration, insomnia, overeating, and weight gain, among others.
Serotonin levels are usually low due to a lack of serotonin’s precursor, an amino acid known as tryptophan. Poprawski told Live Science that this can happen due to low levels of vitamin B6, folic acid or magnesium, a diet high in sugar, excessive alcohol and smoking.
“Serotonin production in the brain can be increased, at least theoretically, by dietary intake of tryptophan,” she said. “This serotonin precursor can enter the brain, but the carrier process also facilitates the entry of other, competing amino acids. In practice, the concentration of tryptophan in blood plasma will be directly affected by the concentration of competing amino acids.” Even when tryptophan enters the blood, it must compete with other amino acids to be absorbed into the brain, where it can be used to produce serotonin.
So in theory it is possible to “enhance” serotonin production by eating foods high in tryptophan, but it depends on other foods consumed. Tryptophan is found primarily in protein-rich foods such as poultry, lean pork, lean beef, salmon, soybeans, pumpkin seeds, pumpkin seeds, tofu, and eggs.
But Lakhan said that while we may be able to increase serotonin production, that doesn’t necessarily mean the body will be able to use more, especially if we already have enough.
“You can see evidence of increased serotonin through exercise, diet, nutraceuticals and pharmaceuticals, but that only equates to increasing your body’s available battery, not the full function it enables,” he said. The brain is complex, and serotonin is not only involved in supporting mood. It also helps regulate attention, behavior and body temperature, as well as the production of melatonin, the sleep hormone.
In other words, there may be effective ways we can increase serotonin production and therefore serotonin levels in the body, but that doesn’t necessarily mean it will have a direct effect on your mood.
Last but not least, more research needs to be done in the area of neurotransmitter function and production. If you are concerned about low serotonin levels, talk to your doctor.
This article is for informational purposes only and is not intended to provide medical advice.