How Tryptophan Impacts Your Sleep

I’m sure many of us have heard the word tryptophan before. Does it ring a bell? Or bring back vivid memories of those post-thanksgiving dinner naps? Every year around November, people start talking about the fun fact that tryptophan is the substance in turkey that makes us fall asleep after thanksgiving dinner.

Does tryptophan actually make you sleepy?

Sure, thanksgiving comes with a whole host of other variables that could make you sleepy. The day is full with family, in-laws, lots of other food, wine, and busy kitchen work. Regardless, there is truth to the statement that tryptophan, the amino acid in turkey, makes you sleepy.

Here’s how it works:

Tryptophan is one of the 9 essential amino acids that we must obtain from our diet. It is estimated to make up about 1% of dietary protein intake. More importantly, tryptophan is a precursor to serotonin. (1) Serotonin, commonly regarded as our happy hormone, is a precursor to melatonin, which is elevated when we are in the sleep portion of our sleep-wake cycle.

Because of this vital role in our sleep-wake cycle, insufficient levels of tryptophan can cause detrimental effects to your sleep cycle, energy levels, mood, and concentration (2). And this is common. With our increasingly technology-reliant lifestyles, we are constantly exposed to blue light, which triggers our body to release more daytime neurotransmitters like serotonin, and less melatonin. So, our body often thinks that since it’s still seeing so much light, we should be alive, awake, alert, and enthusiastic (not so much fun when you just want to have a good night’s sleep).

Image from: https://en.wikipedia.org/wiki/Serotonin

So, can tryptophan supplementation improve your sleep?

Because we know that tryptophan ingestion can increase serotonin, thus providing our body with substrate to produce melatonin, it has been researched as a sleep aid. Here are a few studies showing the relationship between sleep quality and duration:

• Usual tryptophan intake from food was positively associated with sleep duration, as seen in NHANES data from 2001 to 2012. (2)
• Blood levels of tryptophan are significantly lower in obese subjects with sleep deficits, as compared to those without sleep deficits. (3)
• Middle aged/elderly patients who consumed a tryptophan-enriched cereal twice a day (120 mg tryptophan) increased their sleep efficiency and sleep time, while decreasing their total nocturnal activity. (4)
• Supplementation with 4 grams of L-tryptophan increased duration of stage-3 daytime sleep compared with placebo. (5)
• A review paper identified that L-tryptophan supplementation at doses of 1 gram or more produces an increase in rated subjective sleepiness and a decrease in sleep latency (time to sleep). (6)
• A study conducted with insomnia patients found that increases in tryptophan intake, either through food sources or pharmaceutical grade supplementation, resulted in significant improvements in subjective and objective measures of insomnia. (7)

If you are someone who is struggling to get to sleep each night, increasing your intake of tryptophan, or supplementing with it is certainly worth a try. Research has shown in several different populations that tryptophan can be beneficial for decreasing time needed to fall asleep, and in increasing sleep quality and duration. Supply your body with the necessary components to regulate its sleep-wake cycle, and you will surely feel better.

References:

1. Melancon, M. O., et al. 2014. Exercise and sleep in aging: Emphasis on serotonin. Pathologie-Biologie 62(5):276–283. doi:10.1016/j.patbio.2014.07.004.
2. Lieberman, H. R., et al. 2016. Tryptophan intake in the US adult population is not related to liver or kidney function but is associated with depression and sleep outcomes. Journal of Nutrition 146(12):2609S–2615S.
3. Samad, N., et al. 2017. Serum levels of leptin, zinc and tryptophan in obese subjects with sleep deficits. Pakistan Journal of Pharmaceutical Sciences 30(Suppl. 4):1431–1438.
4. Bravo, R., et al. 2013. Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans. Age (Dordrecht, Netherlands) 35(4):1277–1285. doi:10.1007/s11357-012-9419-5.
5. Nicholson, A. N., and B. M. Stone. 1979. L-tryptophan and sleep in healthy man. Electroencephalography and Clinical Neurophysiology 47(5):539–545. doi:10.1016/0013-4694(79)90255-4.
6. Hartmann, E. 1982-1983. Effects of L-tryptophan on sleepiness and on sleep. Journal of Psychiatric Research 17(2):107–113. doi:10.1016/0022-3956(82)90012-7.
7. Hudson, C., et al. 2005. Protein source tryptophan versus pharmaceutical grade tryptophan as an efficacious treatment for chronic insomnia. Nutritional Neuroscience 8(2):121–127. doi:10.1080/10284150500069561.