In Taylor Swift’s recent essay for Elle, "30 Things I Learned Before Turning 30," the singer revealed many things about her life, but one surprising discovery is that she’s a fan of particular supplements. "Vitamins make me feel so much better! I take L-theanine, which is a natural supplement to help with stress and anxiety," she wrote. L-theanine isn’t a new thing, but with Swift touting its effects, more people may be wondering about its effects. Science says that L-theanine can have many different effects on the body and nervous system — and that science can be complicated.
The FDA considers L-theanine a generally safe dietary supplement in the U.S., so you don’t need a prescription to use it. (This does not mean that supplements containing L-theanine are regulated or approved by the FDA, which only reviews supplements for safety.) And it’s been the target of a lot of scientific interest because it seems to have many positive effects on human health. In a review of the science around L-theanine in 2019, scientists wrote: "Several studies have reported that the consumption of this amino acid has many therapeutic effects, including improvements in brain and gastrointestinal function, cancer drug therapeutic efficacies, antihypertensive effects, and improved immune function." However, the scientists add that further research has to translate these studies into repeated results in humans.
So what’s the hype about, and is T-Swift really getting her relaxation from a supplement? Here’s what science says about it.
1It’s Naturally Found In Tea
You likely ingest a bit of L-theanine regularly; it’s an amino acid most commonly found in both green and black teas. It’s one of the main active ingredients in tea, alongside others like catechins. Chocolate companies have been adding it to very dark high-cacao content chocolate to observe the health benefits, and a study (using chocolate provided by The Hershey Company, which reviewed the study before publication) found that chocolate spiked with L-theanine actually seems to help heart function and lower blood pressure. If you’re a tea drinker, though, that’s likely where you’re getting most of your dosage.
2Its Potential Effects On Anxiety Are Mixed
Green tea in particular is meant to be calming, and it’s theorized that L-theanine may be the reason why. However, while the overall picture is pretty positive, studies on the issue have had mixed results. A study in 2007 gave 12 people a stressful task, and found that L-theanine reduced their heart rates and levels of stress hormones in their saliva. People given a multitasking stressful task in a 2016 study also reported lower levels of stress when they were given an L-theanine drink an hour beforehand, and their saliva showed lower levels of stress hormones up to three hours afterwards.
However, another study in 2004 found that L-theanine might be most relaxing when you’re calm, not when you’re doing something stressful. And the latest research from March 2019, published in Journal of Psychiatric Research, found that when it came to people with generalized anxiety disorder, treatment with L-theanine didn’t make any apparent difference in their symptoms, though they did report sleeping a little better than people who were given placebos.
The difference may be that L-theanine can help low levels of anxiety around specific tasks but not more general or disordered anxiety, but it’s not entirely clear.
3Small Studies Indicate It Could Help The Immune System
A review of L-theanine in Beverages in 2016 pointed out that two studies have linked it to better immune system function. In one, elderly patients who had L-theanine supplements were more protected from upper inflammatory tract infections, while in another, people who were given L-theanine and another amino acid called cysteine recovered more effectively after an operation to remove their stomachs. Obviously, these are very specific circumstances, so it’s difficult to generalize to say that L-theanine is great for the immune system in general.
4It Relaxes The Brain’s Activity
One interesting effect of L-theanine is that it appears to change the brain’s electrical activity, which may account for its reputation as a calming substance. In an experiment in 2008, scientists wanted to test whether a small dose of L-theanine, the amount you’d normally get from a cup of tea, would affect alpha brain waves. An increase in alpha brain activity, they explained, "relaxes the mind without inducing drowsiness."
Alpha brain waves occur when you’re very relaxed but still awake, and tend to happen just before you fall asleep. You’re awake, but not very alert or aroused. In the study, even the small amount of L-theanine found in tea increased alpha have levels in peoples’ brains. It’s possible this is why L-theanine may increase feelings of relaxation.
5It May Help Alertness When Combined With Caffeine
Don’t want to chill out? The neurological effects of L-theanine change a lot when they’re combined with caffeine — which, considering the caffeine levels in tea, is how we normally encounter it. A study in 2010 found that combining the two helped people to feel alert and awake, and improved their results when they were switching rapidly between tasks.
It appears that the combination helps us focus with laser-like precision on what we’re doing. In 2018, scientists found that in people who had a combination of the two, their brains were much less likely to respond to distractions, or to show signs of mind-wandering, while doing a task. Want to get some work done without getting distracted by everything in sight? Get some green tea.
6It Boosts The Production Of Some Neurotransmitters
This is a fascinating one: L-theanine appears to boost the levels of some neurotransmitters, the substances that provide communication in the brain and have been linked to mental health. "L-theanine increases dopamine, serotonin, and the inhibitory neurotransmitter glycine," wrote scientists in Nutraceuticals in 2016.
However, there aren’t universal skyrocketing levels across the board, particularly not when it comes to dopamine. Anxiety organization Calm Clinic noted, "L-theanine does not consistently increase the brain’s serotonin ‘happy’ neurotransmitter, associated with positive mood enhancement, but has been shown to result in an increase in some instances." They added that there is "some belief" that L-theanine can increase levels of the neurotransmitter GABA, which is tied to feelings of relaxation, but that this needs further investigation.
If you do want to get hold of some L-theanine for anxiety, it’s a good idea to talk to your doctor first, particularly if you’re already being treated for an anxiety disorder. It’s also worth remembering that while the supplement is considered generally safe, it’s important to do your research on other ingredients that might show up in your supplement formula. Overall, science says Taylor Swift is probably on to something — but as always, take your supplements with a grain of salt.