4 min read

L-Theanine: Everything You Need to Know About This Powerful Supplement

You may have read L-theanine on an ingredient label or have seen it on your Instagram feed, but we wouldn’t be surprised if you don’t know what L-theanine actually is. That’s where we come in!

Read on to get thorough, simply presented answers that will deliver everything you need to know about L-theanine without thrusting you into vivid chemistry class flashbacks.

Infographic on everything you need to know about L-Theanine

What is L-theanine?

L-theanine has emerged as a popular cognitive supplement that’s been claimed to provide some pretty magical benefits, from aiding with sleep to calming stress.. So what is it and where does it come from?

It all begins with tea. 

After regular old water, tea is the second most-consumed drink on the planet (psst, sorry coffee drinkers, and don’t worry, we’ll get to you in a moment, we promise).

Image of green clay tea kettle and mug

Tea is widely recognized as a potent source of antioxidants. But along with its antioxidant-rich properties, tea also contains an amino acid called L-theanine. Bingo.

L-theanine is believed to positively affect brain function in humans and sure enough, evidence from electroencephalograph (EEG) studies reveals that it does impact our minds.

But, here’s the real magic. L-theanine works to increase alpha frequencies in the brain which can relax us and help us stay focused. Yet, unlike other relaxing supplements, L-theanine doesn’t put you in a tired and drowsy state. You get all the calm, but none of the sleepiness. Another study suggests that L-theanine directly impacts our ability to pay attention and be more alert.

Where to get L-theanine

The issue with tea is that it only has about 20 mg of L-theanine per cup and L-theanine appears to work better in higher doses to affect brain and cognitive function.

L-theanine is not produced naturally by your body, but it can be found in green tea leaves, black tea leaves, and certain kinds of mushrooms.

Today, you can buy L-theanine in tablet or powder form and find it as an addition to healthy drinks or nootropic beverages. Supplement companies offer L-theanine in doses ranging from 50 mg up to 500 mg.

Image of Cafe Mocha Soylent 

At Soylent, we add L-theanine to all the drinks in our lineup that have caffeine in them, due to the compelling research on what L-theanine does when paired with caffeine. 

Which leads us to...

L-theanine: Caffeine’s Level-headed Friend

Hey coffee drinkers, we said we’d get to you, didn’t we? 

7 in 10 Americans drink coffee every week and 63% of Americans drink it daily. For most of us, coffee is the morning elixir of life—the stuff that makes us bright-eyed and bushy-tailed and ready to take on the world.

Yet, have you ever finished a coffee only to find that you’re feeling not merely alert and awake but also uncomfortably jittery and anxious?

This is because caffeine activates your “fight or flight” response. The best L-theanine use is alongside your morning cup of joe. Research shows that when L-theanine foods or supplements are paired with caffeine, the two team up to improve cognitive performance and alertness while erasing the jittery, anxious feelings that can arise when caffeine is consumed by itself.

List of the benefits and properties of Soylent

We intentionally added 75mg of L-theanine to both our Cafe Mocha and Complete Energy drinks. As mentioned, any Soylent product that contains caffeine also comes with L-theanine to balance it out.

The Tip of the Iceberg

L-theanine is proving to be a tried-and-true pairing with caffeine and a popular supplement in general. But it may have more benefits than what has been discovered thus far.

The National Institute of Health reported the findings of a randomized control trial in which participants were given 200 mg of L-theanine per day for four weeks. The study was constructed around uncovering L-theanine’s potential to reduce stress, anxiety, and depression, and to raise overall cognitive function.

Image of woman smiling

In the presence of L-theanine, participants reported lower and better scores on the Self-rating Depression scale, State-Trait Anxiety Inventory-trait, and Pittsburgh Sleep Quality Index. In terms of cognitive measurements, both verbal fluency and executive function scores went up with the intake of L-theanine.

The abstract of the study concluded by saying, “our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.” 

According to Memorial Sloan Kettering Cancer Center’s website, there are no reported side effects or negative symptoms from taking L-theanine, though excessive consumption of green tea can have side effects due to the levels of caffeine present. 

Only time will tell the extent to which L-theanine can benefit us. For now, we’re happy to know it’s positively impacting our brain function and mellowing out our morning cup of joe. 


L-theanine is an amino acid found in tea that’s making a big splash as a useful supplement in beverages, mixed into nootropic blends, and by itself as tablets or in powder form. L-theanine’s primary uses are for relaxing and focusing the mind and potentially helping with sleep and cognitive function. 

When paired with caffeine, L-theanine works to counterbalance and soften the jittery effects caffeine can have on its own. 

This wraps up everything you need to know about L-theanine. Are you keen to give it a try? Pick up a bottle of our Cafe Mocha and see if you can feel the focusing effects of L-theanine paired with caffeine.