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L-tryptophan is an essential amino acid that is a precursor to the brain neurotransmitter serotonin. A diet that’s deficient in tryptophan reduces serotonin production in the brain and can lead to depression, anxiety, mood disorders, insomnia, poor cognition, and other brain conditions. On the contrary, research shows that a high-tryptophan diet can have a positive effect on reducing such symptoms.
So how do we get L-tryptophan in our diets? And if we aren’t getting enough, do tryptophan supplements help? We’ll start with the food part of the equation.
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10 Tryptophan Foods… and Supplements
When we think of tryptophan foods, turkey typically comes to mind first. But this powerful little brain nutrient also can be consumed via other food sources along with supplements.
Foods highest in L-tryptophan include:
One important note to keep in mind is that many of these tryptophan foods are all also high in other amino acids, which can compete with L-tryptophan for absorption in the gut. Therefore, the best way to improve L-tryptophan absorption is to eat meals high in carbohydrates and lower in competing protein sources (hence, the enhanced sleepiness effect when consuming L-tryptophan in turkey with other carbohydrates during the holidays).
The best way to improve your L-tryptophan levels is to take high-quality tryptophan supplements.
How Do Tryptophan Supplements Work?
Tryptophan supplements are typically available in 500 mg and 1000 mg tablets and capsules. You should take L-tryptophan on an empty stomach, preferably 15 minutes before mealtimes or two hours after eating to increase the absorption.
While carbohydrates increase the absorption, they generally aren’t recommended as a high-carb diet can actually make mood and depression symptoms worse. As long as you take an L-tryptophan supplement on an empty stomach, the amino acid will be absorbed properly.
Tryptophan Supplements: What Dosage?
For sleep disorders, 1,000 mg of tryptophan is recommended 30 minutes to one hour before bedtime. Start with 1,000 mg (1 gram) and increase each night by 500 mg, as needed, up to 15 grams total, until the desired dosage for sleep is achieved.
For depression, anxiety, or other mood symptoms, try 500 mg of tryptophan three times daily, and take the last dose 30 minutes to one hour before bed time.
The benefits of consuming either tryptophan foods and supplements are wide-ranging:
- Tryptophan reduces depression and improves mood. A large meta-analysis study published in The Journal of Clinical Psychiatry showed that people with low concentrations of L-tryptophan in their blood were more apt to developing major depressive disorder. This makes sense when you understand that a deficiency of the brain chemical serotonin is one of the main causes of depression. L-tryptophan converts into serotonin through a multi-step process using enzymes called tryptophan hydroxylase and aromatic L-amino acid decarboxylase. This complex chemical process is not what’s important–what is important are the end results. Sufficient levels of L-tryptophan in the body can reduce depression and anxiety. Furthermore, another in-depth study about L-tryptophan published in the journal Nutrients in 2016 showed the link between L-tryptophan depletion and mood. According to the researchers, it was clear that improved L-tryptophan levels were consistently associated with better mood. (See also “Serotonin Supplements to Treat Depression, Anxiety, and Insomnia Yourself.”)
- Tryptophan plays a role in cognition. Remember that L-tryptophan is the chemical precursor to serotonin. This brain neurotransmitter plays a significant role in cognitive performance as low serotonin levels are correlated to impaired memory. In a 2016 study published in the journal Current Opinion in Clinical Nutrition & Metabolic Care, researchers noted, “It has become more and more evident that there exists an association between food and brain functions like mood and cognition. Tryptophan represents a key element for brain functioning, because of its role as a precursor for production of neurotransmitter serotonin (5-hydroxytryptamine). . . . Not only a diet rich in tryptophan but also a diet rich in antioxidants can have a positive impact on mood and cognition. This could be of special relevance for individuals who present with low grade inflammation conditions.”
Another study published in 2017 revealed that the tryptophan metabolic pathway could be a novel target for creating new drugs designed for treatment of Alzheimer’s disease.
- L-Tryptophan may provide help for insomnia. One of the key benefits of consuming tryptophan foods or tryptophan supplements—with significant research supporting its efficacy—is that it’s a natural remedy for insomnia. Scientists have verified that L-tryptophan improves both the time it takes to fall asleep as well as the quality of sleep. L-tryptophan is effective in reducing sleep onset time on the first night of administration in doses ranging from 1 to 15 grams.(For more on insomnia and sleep hygiene, see What Is Insomnia? Symptoms, Treatment, and Sleep-Saving Tips.
L-tryptophan should be used with caution with other anti-depressants like citalopram (Celexa), desvenlafaxine (Pristiq), vilazodone, linezolid, and phenelzine because of increased risk of a serious condition called “serotonin syndrome,” which is caused by excessive serotonin in the brain. The degree of serotonin syndrome symptoms can range from mild to severe and can include high body temperature, agitation, increased reflexes, tremor, sweating, dilated pupils, and diarrhea.
A side effect of taking L-tryptophan supplement is weight loss, which could actually be a health benefit for those who are overweight. Additional side effects include dizziness, drowsiness, fatigue, nausea, and heart palpitations.
Talk to your doctor before taking tryptophan supplements, and do not take more than the recommended dose, especially when combined with tryptophan foods. Consuming too much tryptophan from supplements can cause overdose symptoms, such as trembling, shivering, overactive reflexes, confusion, fever, vomiting, diarrhea, restlessness, and agitation.
 Ogawa, S., Fujii, T., Koga, N., Hori, H., Teraishi, T., Hattori, K., . . . Kunugi, H. (2014). PlasmaL-Tryptophan Concentration in Major Depressive Disorder. The Journal of Clinical Psychiatry, 75(09).
Originally published in 2017, this post is regularly updated.