Tryptophan’s Role in Anxiety

Tryptophan is known for its ability to make those who consume it in large amounts experience a sleepy sensation. It’s the fun fact we hear every thanksgiving, citing that turkey is responsible for delivering tryptophan to our cells and making us all want to take a nap after dinner. This is because this amino acid, tryptophan, is a precursor to our neurotransmitters, serotonin and melatonin, which regulate our sleep-wake cycle.

Why should we care about tryptophan? Well, as we age, transport of tryptophan across the blood-brain barrier begins to decrease.(1) In addition, oxidative stress can decrease activity of tryptophan hydroxylase, the rate-limiting enzyme responsible for producing both serotonin and melatonin in our cells.(2) Which means that, if we are under oxidative stress as many are, our tryptophan enzymes may not be as active, thus hindering our production of both serotonin and melatonin. As we age, and throughout our lives, it becomes increasingly important to optimize both our tryptophan intake and our antioxidant status.

Could tryptophan’s relaxing effects help with anxiety?

This question of whether tryptophan can help with anxiety is relevant to the more than 40 million adults in the US who suffer from anxiety each day. We know that serotonin and melatonin regulation play a role in mood and cognitive function in addition to sleep regulation, which points toward potential for tryptophan supplementation to be beneficial in individuals with anxiety.

Research has certainly shown that tryptophan CAN play a role in mental health in several ways.

• In mice, we have seen that a lack of tryptophan intake can induce anxiety-like effects. (3)
• A systematic review found that plasma tryptophan was inversely related to postnatal depression scores in mothers in three out of four studies. (4)
• Another study found that tryptophan depletion can result in several negative impacts to mental health, including a significant reduction in serotonin release, mood lowering, memory impairment, and worsening of depression in untreated depression patients. (5)
• In IBS patients, tryptophan depletion resulted in worse anxiety symptoms than those patients who were not depleted. (6)

So, we know that modifying concentrations of tryptophan can alter our mental state overall through decreasing or increasing production of serotonin. But what is its role in anxiety?

Tryptophan intake and anxiety symptoms

Here are some studies that have looked at dietary tryptophan and its impact on anxiety.

• Participants who were given tryptophan-enriched cereals at breakfast and dinner (totaling 120 mg tryptophan/day) saw significant decreases in anxiety about events in comparison to when they were given non-enriched cereals (7).
• People who followed a high-tryptophan diet (10 mg/kg of body weight per day) saw significant improvements in self-rated anxiety and significantly higher positive mood scores, compared to when they were randomized to a lower tryptophan diet (<5 mg/kg body weight per day). (8)

In addition, Trudy Scott, a colleague of Dr. Brown, has several impressive documented success stories of women improving their anxiety symptoms with a combination of dietary intervention and tryptophan supplementation. You can read her latest case here.

Tryptophan and mood overall

In addition to tryptophan’s role in anxiety and depression, there are some impressive findings that show it can impact our overall mood for the better. Here are a few astonishing studies:

• Quarrelsome individuals who were given tryptophan supplements of 3g/day total (spread out over 3 doses) saw increases in positive mood and pleasantness. (9)
• Tryptophan supplementation increased interpersonal trust in a study of 40 healthy adults. (10)
• In a study of 32 adults, just 800 mg of tryptophan supplementation increased how much money participants donated to charity, compared to placebo. (11)

Overall, tryptophan supplementation and/or tryptophan-rich diets show promising results in the area of mental health. It is increasingly important each day to optimize our intake of tryptophan, especially in today’s modern world where stress—both oxidative and mental—is on the increase.

References:

1. Porter, R. J., et al. 2005. Effects of acute tryptophan depletion on mood and cognitive functioning in older recovered depressed subjects. American Journal of Geriatric Psychiatry 13(7):607-615. doi: 10.1176/appi.ajgp.13.7.607.
2. Hussain, A. M., and A. K. Mitra. 2004. Effect of reactive oxygen species on the metabolism of tryptophan in rat brain: Influence of age. Molecular and Cellular Biochemistry 258:145-153. org/10.1023/B:MCBI.0000012849.16750.00.
3. Zhang, L., et al. 2006. Rats subjected to extended L-tryptophan restriction during early postnatal stage exhibit anxious-depressive features and structural changes. Journal of Neuropathology & Experimental Neurology 65(6):562-570. doi.org/10.1097/00005072-200606000-00004.
4. Trujillo, J., et al. 2018. A systematic review of the associations between maternal nutritional biomarkers and depression and/or anxiety during pregnancy and postpartum. Journal of Affective Disorders 232:185–203. doi:10.1016/j.jad.2018.02.004.
5. Bell, C., et al. 2001. Tryptophan depletion and its implications for psychiatry. The British Journal of Psychiatry: The Journal of Mental Science 178:399–405. doi:10.1192/bjp.178.5.399.
6. Shufflebotham, J., et al. 2006. Acute tryptophan depletion alters gastrointestinal and anxiety symptoms in irritable bowel syndrome. The American Journal of Gastroenterology 101(11):2582–2587. doi:10.1111/j.1572-0241.2006.00811.x.
7. 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.
8. Lindseth, G., et al. 2015 The effects of dietary tryptophan on affective disorders. Archives of Psychiatric Nursing 29(2):102–107. doi: 1016/j.apnu.2014.11.008.
9. aan het Rot, M., et al. 2006. Social behaviour and mood in everyday life: The effects of tryptophan in quarrelsome individuals. Journal of Psychiatry and Neuroscience 31(4):253–262.
10. Colzato, L. S., et al. 2013. Tryptophan promotes interpersonal trust. Psychological Science 24(12):2575–2577. doi:10.1177/0956797613500795.
11. Steenbergen, L., et al. 2014. Tryptophan promotes charitable donating. Frontiers in Psychology 5:1451. doi.org/10.3389/fpsyg.2014.01451.