Medically reviewed by Katelyn Hagerty, FNP
Written by Our Editorial Team
Last updated 12/11/2022
There are lots of supplements out there that claim they can help with stress and anxiety. In fact, if you walk down any vitamin aisle, you’ll see lots of different products with labels claiming to have a calming effect.
One supplement you may come across is L-theanine. Many people say supplements containing this substance can have positive effects on mental health, the body and the nervous system — and that it can help with anxiety.
But is the hype deserved? Keep reading to learn more about what L-theanine is, whether it is effective for symptoms of anxiety and what the right dosage is.
L-theanine (sometimes just called theanine), is an amino acid that can be found in green tea and certain mushrooms. It can also be found in supplement form.
Both L-theanine and caffeine (which green tea is high in) are thought to have beneficial effects on cognitive function and mood.
Wondering how it works? Not to get too science-y on you, but it’s a non-protein amino acid that crosses the blood-brain barrier. Once it crosses that barrier into the brain, it has neurophysiological and pharmacological effects — including a potentially calming effect.
It is also related to glutamine, which many think increases levels of a neurotransmitter called GABA, and the feel-good neurotransmitters serotonin and dopamine.
It is generally considered to be a safe dietary supplement. But you should know that supplements containing L-theanine are not regulated or approved by the FDA.
Some potential beneficial effects of theanine supplements include:
Help with treating cancer: Animal studies done in the lab suggest it could have anti-tumor properties, but human research needs to be conducted.
Stroke risk reduction: Studies conducted in Japan found that green tea consumption may lower risk of stroke. However, it’s not clear if it was the L-theanine in the tea that contributed.
In addition to these benefits, many people say L-theanine administration can help with psychological stress and anxiety.
You probably know that just because people say something, it’s not necessarily true. So, can theanine really help with anxiety? To answer this question, it’s best to turn to research.
Before diving in, you should know more research needs to be done to definitively say if L-theanine can help with anxiety in humans. But with that caveat, here’s a look at the studies that have been done.
Remember when we mentioned that L-theanine is often found in tea? Research suggests that sipping tea that contains L-theanine can relax the mind. The catch: This effect has been found with higher doses than are usually found in tea.
In a review of five randomized controlled trials of 104 participants total, researchers found that L-theanine may lead to lowered stress and anxiety for people going through times of stress.
Another study looked at people living with schizophrenia and schizoaffective disorder and found that L-theanine administration decreased anxiety in those people.
As you can see, these clinical studies and clinical trials suggest promise when it comes to L-theanine having an anti-stress effect or lowering anxiety symptoms. However, more research needs to be done on this amino acid to conclude if it can really ease anxiety in otherwise healthy adults.
L-theanine supplements are usually found in doses between 50mg and 200mg, but there are no guidelines in place for effective theanine dosage ranges.
One way to determine what may be an effective dosage to lower anxiety levels would be to look at what dosage of L-theanine was used in the studies. In one of the studies that found L-theanine may lower stress, participants took 200mg a day.
For context, the average cup of green tea contains between eight and 30 mg of L-theanine.
If you are interested in taking L-theanine for any reason, you should speak to a healthcare professional about what dosage would be best for you.
Wondering what adverse effects may come along with taking L-theanine? To be honest, there aren’t many.
Some suggest looking at the acute effects of green tea or green tea extract, as you may experience the same effects when taking a L-theanine supplement.
Potential side effects of green tea leaves are nausea and stomach pain. Green tea can also have negative side effects on your sleep. This is due to the effects of caffeine, which green tea has a good deal of.
Those who are pregnant or breastfeeding should also avoid L-theanine supplements because there just isn’t enough research that shows it is safe for these people.
If you are taking other medications, you should check in with a healthcare provider before you start taking -theanine. This is because it can potentially cause harmful drug interactions. For example, theanine can have negative effects when combined with medications taken for high blood pressure. It can also be problematic when taken with sedatives.
Finally, you should always disclose any health conditions you have (beyond anxiety) to a healthcare professional before you start taking something new. It’s possible that any supplements or new medications you take may have adverse side effects if you have certain health conditions.
Generally speaking, the pharmacological effects of prescription drugs for anxiety, like sertraline, have been proven to be an effective way to treat anxiety. However, some people prefer to turn to natural supplements like theanine.
But does L-theanine really work to lower anxiety levels? There are some small studies — one of which was done on animals — that seem to suggest that it could.
There are no recommended dosage guidelines for taking L-theanine for anxiety. It may also interact poorly with other medications, such as high blood pressure medications.
Because of this, it’s important to consult a mental health professional before you start taking L-theanine or any other supplement for anxiety. If you’d like, you can schedule an online consultation to discuss your anxiety and what supplements or medication may be most beneficial.