Editor's note: This article originally appeared on NaturalProductsInsider.com, the sister website to Food & Beverage Insider.

L-theanine is the amino acid found in green tea that makes you relaxed but without feeling drowsy. That has made it a popular ingredient in stress relief and nootropic supplements. But what’s the best dose to give a person its experiential effects—and what counts as pixie dusting a product with the powerful ingredient name but with a meek and mild dose?

A regular cup of green tea naturally contains about 25 mg of L-theanine. In supplements, you can find pills with as much as 500 mg per serving.

So what does the science say? In 2016, a review of five randomized, controlled trials among about 100 people found positive effects on taming acute stress and anxiety using between 200 and 400 mg/day.

At a dose of only 50 mg, within 40 minutes and lasting for at least 105 minutes (the extent of the study), L-theanine has been shown to jack up the pattern intensity of alpha-wave production in the cerebral cortex area of the brain. Alpha waves are a hallmark of an increased relaxed but alert mental state. Researchers concluded that L-theanine has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention. 

One human study using 200 mg/day on 12 people found anti-stress effects after a single dose.

A double-blind, placebo-controlled study among 34 healthy adults who drank a beverage containing 200 mg L-theanine found anti-stress effects that started one hour after consumption, with effects that lasted until the three-hour mark.

Another placebo-controlled study gave 200 mg L-theanine twice daily (so 400 mg/day total) to 20 fifth-year university students during pharmacy practice. The students were tracked from one week prior to the pharmacy practice and continued for 10 days in the practice period. Subjective stress was significantly lower in the L-theanine group compared to placebo.

A dose of 200 mg promotes a reduction in resting heart rate, which further highlights its relaxing properties.

At doses between 250 and 400 mg, L-theanine has been found to improve sleep quality.

Stress is the primary application for which L-theanine is used, with sleep probably the second most popular use. 

So formulating with L-theanine for sleep products requires a higher dose than using it for a stress-relief product. 

Nootropic formulations

L-theanine has gained popularity in nootropic formulations because of a number of studies that combine it with caffeine. The active ingredient in coffee is a well-known stimulant, but combining caffeine with L-theanine, usually at a 1:2 ratio, so usually 100 mg caffeine (the typical amount in a cup of coffee) with 200 mg L-theanine, is where nootropic effects lie.

Here, what research shows is that the L-theanine cuts caffeine’s jittery effects while still leading to positive mental performance around attention and mood.

And just so you don’t think the cognitive enhancement was all about the caffeine, a study using only L-theanine found a single dose of L-theanine reduced the reaction time to attention tasks, while after 12 weeks of taking 100 mg/day L-theanine it increased the number of correct answers and decreased the number of mistakes in working memory tasks.

Is matcha tea the next great nootropic drink?

Interestingly, L-theanine and caffeine are present together, along with epigallocatechin gallate (EGCG), a polyphenolic antioxidant, in the trending beverage, matcha tea.

One human placebo-controlled study used matcha in tea and as a food in a matcha tea bar containing 4 grams matcha tea powder. It found the matcha products were better than placebo in attention and cognitive speed in response to stimuli. However, there was no change in mood—and, of note, while both matcha-infused products were more effective than nothing, the drink was better than the food, highlighting the bioavailability-boosting effects of a liquid delivery format.

In an April 2021 study, researchers found that matcha helps ease mild stress-related cognitive decline and improves reaction time among a very important consumer demographic: young adults. Researchers recruited 42 participants ages 25 to 34 years, who consumed 2 grams of ITO EN’s ceremonial-grade matcha daily for two weeks. ITO recently entered a partnership with Taiyo Int'l, which is the pioneering supplier of the Suntheanine brand of L-theanine. Participants who consumed ceremonial-grade matcha daily had higher attentional function than the placebo group, and also experienced faster reaction times and were better able to identify positive emotions, which may indicate a happier perspective. 

The ceremonial-grade matcha used in this study contains about 50 mg L-theanine per two-gram dose of matcha. As previously noted, this is the lowest dose of L-theanine shown to increase calming alpha brain waves. 

Adding an additional 50–150 mg L-theanine may be the wise formulator idea to get the mood and focus benefits just exactly right. This would correlate to the 200 mg L-theanine found to give anti-stress effects after a single dose. 

This is an important consideration when deciding on product format, because beverages are more likely to be taken in a single-use, occasional setting, while a pill-style supplement format could be seen as being a more chronic-intake product. 

It's important to formulate products that work. So-called pixie dusting—using a sexy ingredient but at levels below an efficacious dose—do real harm to an entire category. If a consumer tries a stress-relief supplement, or a nootropic gummy, or a performance beverage, and does not get the effect as advertised, that consumer may be lost forever, and not just to that brand that blew it but to the entire category.