Selective serotonin reuptake inhibitors, or SSRIs, increase the brain’s levels of the mood-enhancing neurotransmitter serotonin. L-tryptophan is an essential amino acid that forms the starting point for serotonin synthesis. As too high levels of serotonin in the brain can lead to cardiac arrest, adding L-tryptophan to your diet while taking an SSRI is unsafe.
Low levels of serotonin are strongly associated with depression and anxiety disorders. SSRIs increase the brain’s levels of serotonin by preventing serotonin transporters in the brain from deactivating serotonin. Serotonin cannot enhance the neuron signal when it is inside the neurons. As the serotonin transporter transports serotonin back into the neurons, this molecule deactivates serotonin. By blocking the serotonin transporter, SSRIs increase the brain’s levels of active serotonin.
L-Tryptophan and Serotonin Synthesis
When you consume food or supplements containing the essential amino acid L-tryptophan, the amino acid enters the bloodstream through the walls in the intestinal tract. If L-tryptophan crosses the brain-blood barrier, the brain can convert it into 5-hyrdoxytryptophan, or 5-HTP, and then into serotonin. There is some evidence indicating that L-tryptophan taken as a supplement crosses over into the brain. So, taking L-tryptophan as a supplement may raise the brain’s levels of serotonin.
Serotonin syndrome is a kind of serotonin poisoning that usually occurs as a result of an overdose of a serotonin-enhancing drug or drug interactions. Two drugs, or a drug and a supplement, that both enhance serotonin levels can cause the syndrome. Serotonin syndrome results in an increase in heartbeat, agitation and high fever. The syndrome can lead to cardiac arrest. One of the most famous cases of a death as a result of serotonin syndrome is that of Libby Zion. Libby was hospitalized and given the morphine-like pain medication meperidine. This drug interacted with an antidepressant she was already taking and lead to cardiac arrest.
Because serotonin syndrome is a very serious condition, it is unsafe to take an antidepressant that enhances serotonin levels together with a supplement that may enhance serotonin levels. Tryptophan is essential to the synthesis of serotonin. Since SSRIs work only if the brain synthesizes serotonin, tryptophan is essential to the function of SSRIs. To avoid a tryptophan deficiency, incorporate tryptophan-rich foods, such as chickpeas, whey protein, buckwheat, sunflower seeds, flaxseeds and flax oil, into your diet. As you would have to eat huge quantities of these foods to acutely raise your brain’s levels of serotonin, adding tryptophan foods to your diet is a safe way to ensure that you get enough tryptophan but not too much.
- Drugs.com: L-Tryptophan
- "The New England Journal of Medicine”; The Serotonin Syndrome; E.W. Boyer, et al.; March 2005
- “Journal of Neurology, Neurosurgery and Psychiatry”; Effect of Tryptophan Administration on Tryptophan ... ; S.N. Young, et al.; April 1981
- "Journal of Psychiatry and Neuroscience"; How to Increase Serotonin in the Human Brain without Drugs; Simon N. Young; November 2007