The year is 2019. It is Thanksgiving. Your family has gotten together for a massive Thanksgiving feast. You just finished your 3rd helping of turkey with all the fixings. You're now sitting on the couch with the top button of your pants undone wondering two things:
- Why didn't you wear sweat pants?
- How is it that turkey always makes you feel so pleasantly warm and sleepy?
I have the answers:
- Because the pandemic hasn't struck yet and people still expect you to wear regular pants most of the time.
- A magical little amino acid called tryptophan.
What does a tryptophan do?
Tryptophan is a key nutrient for happy, calm brain chemistry and for supporting your body's stress response and immune system.
It is an essential amino acid, which means your body can't make it, you have to get it from your diet or supplements.
Once it's in you, it will go down one of three pathways:
- To become serotonin and melatonin
- To build proteins (like muscle tissue)
- The kynurenine pathway - which makes important molecules for stress response and the immune system
The majority of tryptophan is used in the 3rd pathway - Kynurenine. This increases under conditions of chronic stress and infections and limits the amount available for making serotonin and melatonin in the brain (3).
What's the big deal with serotonin?
Serotonin acts as both a hormone and a neurotransmitter. In plain terms, that means it is both a brain chemical affecting mood, behavior, sleep, and cognitive function, AND it works as a chemical messenger affecting glands and organs throughout the body (4).
Serotonin is a major multitasker. It is involved in:
- mood regulation
- sex drive
- sexual function
- body temperature regulation
- heart rate
- pain perception
- stress response
Low levels of tryptophan can lead to lower serotonin levels (3). This has been linked to mood disorders such as anxiety and depression, sleep issues, digestive problems, and sexual dysfunction (4). The way that serotonin is made and used in the body is complex and still an area of intense research. One thing we know is that when it's not working properly, it causes problems.
How tryptophan helps with sleep
As previously mentioned, we need to get enough tryptophan to make serotonin and melatonin, as well as to support making proteins and proper stress response. When you are sick or stressed, you burn through your tryptophan faster and need to get more of it.
Athletes and active people who are eating lots of protein and/or supplementing with BCAAs can benefit even more from tryptophan supplementations because BCAAs compete with tryptophan for absorption in the brain (3).
Traditional thanksgiving meals pack a perfect storm for getting lots of tryptophan into the brain. The carbs in the potatoes, sweet potatoes, stuffing and pumpkin pie increase insulin. Insulin tells your cells to take the sugars and amino acids (protein parts) out of your blood stream to use them. But insulin doesn't clear tryptophan from your blood stream. So everything else gets cleared out, while tryptophan gets an open highway to your brain. This floods the brain with the materials it needs to make lots of serotonin and melatonin(1). The result is your happy and sleepy thanksgiving glow.
Studies have shown that supplementing with tryptophan can help with your mood and sleep any day of the year.
In over 4 decades of research, studies as far back as 1970 have shown beneficial effects using L-tryptophan supplements in healthy adults as well as insomniacs (8). Benefits include increasing serotonin and melatonin in the brain, increased average total sleep time, increased drowsiness before bed, improved sleep quality, and increased deep sleep. All of this without any morning 'hangover' or compromised next day performance (8).
One study involving 35 adults, found that eating tryptophan-enriched cereal at breakfast and dinner helped people to fall asleep faster, sleep longer, and have fewer sleep interruptions (5).
A 2016 review article that analyzed data from over 26 000 Americans found that tryptophan intake was positively associated with increased sleep duration (6).
How to take it
The dosing of tryptophan varies wildly in published research, from 250mg to 5g. I tend to stay on the side of the minimum effective dose, especially when taking supplements with multiple combined ingredients.
Since studies with 250mg have shown improved subjective and objective sleep measures including increased deep sleep, this is what I recommend (9, 10).
- Spring, B. “Recent research on the behavioral effects of tryptophan and carbohydrate.” Nutrition and health vol. 3,1-2 (1984): 55-67. doi:10.1177/026010608400300204
- Davis, Ian, and Aimin Liu. “What is the tryptophan kynurenine pathway and why is it important to neurotherapeutics?.” Expert review of neurotherapeutics vol. 15,7 (2015): 719-21. doi:10.1586/14737175.2015.1049999
- Höglund, Erik, Øyvind Øverli, and Svante Winberg. "Tryptophan metabolic pathways and brain serotonergic activity: a comparative review." Frontiers in endocrinology 10 (2019): 158.
- Berger, Miles et al. “The expanded biology of serotonin.” Annual review of medicine vol. 60 (2009): 355-66. doi:10.1146/annurev.med.60.042307.110802
- Bravo, R et al. “Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans.” Age (Dordrecht, Netherlands) vol. 35,4 (2013): 1277-85. doi:10.1007/s11357-012-9419-5
- Lieberman, Harris R et al. “Tryptophan Intake in the US Adult Population Is Not Related to Liver or Kidney Function but Is Associated with Depression and Sleep Outcomes.” The Journal of nutrition vol. 146,12 (2016): 2609S-2615S. doi:10.3945/jn.115.226969
- Wyatt RJ, Engelman K, Kupfer DJ, Fram DH, Sjoerdsma A, Snyder F. Effects of L-tryptophan (a natural sedative) on human sleep. Lancet. 1970 Oct 24;2(7678):842-6. doi: 10.1016/s0140-6736(70)92015-5. PMID: 4097755.
- Silber, B. Y., and J. A. J. Schmitt. "Effects of tryptophan loading on human cognition, mood, and sleep." Neuroscience & biobehavioral reviews 34.3 (2010): 387-407.
- Hudson, Craig, et al. "Protein source tryptophan versus pharmaceutical grade tryptophan as an efficacious treatment for chronic insomnia." Nutritional Neuroscience 8.2 (2005): 121-127.
- Hartmann, E. R. N. E. S. T., and CHERYL L. Spinweber. "Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake." The Journal of nervous and mental disease 167.8 (1979): 497-499.