What You Should Know Before Taking a L-Theanine Supplement, According to Dietitians

THE INTERNET IS all about wellness these days. With so many stressors weighing us down in times like these, we’ll try just about anything to find a sense of calm in a hectic world.

Right now, the magic supplement touted for its anxiety-reducing properties on outlets like TikTok and Instagram is L-theanine. It’s not only about stress-relief—it’s also being marketed as the secret weapon in your quest for peak cognitive performance by helping maintain focus. But what is it exactly? And can it really boost your noggin?

Ahead, dietitians reveal what you should know before taking a L-theanine supplement.

What is L-theanine?

KATE INGRAM, M.P.H., R.D., DESCRIBES L-theanine as a compound found in tea that has the ability to help you relax and focus.

“Have a demanding task at work late in the day but don’t want coffee jitters? Tea’s combination of caffeine and L-theanine can give you a calm yet alert mental state that could help boost productivity and effectiveness,” Ingram explains, citing a 2021 study on caffeine and L-theanine published in Cureus.

Are There Any Benefits to Taking L-theanine?

AS MENTIONED ABOVE, L-theanine may help people feel focused and calm, because science has shown that it can pass through the blood-brain barrier. Because of this potential perk, L-theanine is now also sold as a supplement. In supplement form, it typically has about 200 mg per serving, quite a bit more than the standard 6 mg or so in a cup of tea.

There’s some science to suggest brain benefits: People who supplement with L-theanine may sleep more soundly, stressless, think better, and potentially stave off mental decline. “But the key word is suggest,” says Perri Halperin, R.D., a clinical nutrition coordinator at MountSinai Health System in N. Y. C.

No supplement has yet been proven to boost your immunity. Yes, a 2023 study review did find that L-theanine supplementation can help the immune system function—in livestock.

What Are The Risks of Taking L-theanine?

“L-THEANINE IS GENERALLY recognized as safe, however it is always best to consult your healthcare provider before starting any supplement,” says Ingram. This is especially the case if you have underlying health conditions or are taking other medications. L-theanine supplements could interact with some anti-anxiety, blood-pressure, and sleep meds. Side effects include headaches, dizziness, nausea, and jitteriness.

Do I Really Need to Take L-theanine?

AS INGRAM PUTS it, “why start a supplement when you can just have a cup of tea?” Plus, with tea you have so many other health benefits such as its potential to improve gut health, promote weight loss, and protect you against chronic disease, Ingram says.

Bottom line: You might get a more set dose of L-theanine if you take it in supplement form, but you’ll be paying a lot for something you can get from just brewing a cup of tea. “Tea is certainly a cost-effective way to give it a try,” Ingram says. And, as always, talk to your doctor or a registered dietician before beginning any type of supplement to ensure that it’s something that will work best for you.

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