L-Theanine is arguably an underrated tool when it comes to managing stress and anxiety. It is not an overly popular option amongst the general population, but it consistently appears to have benefits. There also appears to be minimal downsides.
In this post, the research on L-Theanine will be discussed and we will explore whether it is worth taking.
What is L-Theanine
L-Theanine is an amino acid that is naturally found in certain plants. It is consumed commonly in the form of tea.
Although we naturally consume it through tea, the dosage in tea is usually below the optimal dosage for benefits. The content in tea varies, but it is usually <50mg, while the clinically relevant dosage that is often used in research finding benefits is >100mg.
Theoretically, the benefits of L-Theanine come from increased alpha-waves in the brain, which is associated with relaxation.
Stress
Improvements in stress and anxiety are the main benefits of L-Theanine. I will go through these separately to look at the research on each topic individually.
- A 2007 study on 12 people who took 200mg of L-Theanine found reductions in stress.
- A 2016 randomised placebo-controlled trial of 34 people taking L-Theanine also found reductions in stress.
- A 2013 study designed around a high-stress situation (university students on placement) found that 200mg of L-Theanine per day significantly reduced perceived stress compared to placebo.
- A 2019 study using 200mg of L-Theanine compared to placebo in a total of 30 people also had similar findings.
There are more studies beyond those four, but some consistent themes emerge. Every study I’ve seen on L-Theanine and stress shows improvements, with most using a dosage around 200 mg.
Anxiety
Stress and anxiety are often grouped together when people talk about L-Theanine. The research on anxiety-related outcomes is not nearly as promising though.
A 10-week randomised controlled trial involving 450-900mg L-Theanine per day in those with anxiety did not find any advantages over placebo. It did however improve sleep outcomes.
Another study found that 200mg L-Theanine improved relaxation but did not reduce anxiety in experimentally induced anxiety situations.
A 2016 systematic review on the topic of stress and anxiety only found 5 relevant studies in humans that used 200-400mg of L-Theanine. Of those studies, only one involved participants with anxiety, which was the 10-week trial mentioned above.
The four studies that did not involve participants who had been diagnosed with anxiety found improvements in measures of anxiety.
Those improvements are worth noting, but it’s a stretch to say there’s strong evidence that L-Theanine consistently helps with anxiety.
Sleep
L-Theanine does not directly improve sleep. In fact, that is part of its appeal. By helping with relaxation, without having a drowsiness effect, it could be helpful for those who want to perform well in stressful situations.
Although there is no direct effect, research consistently finds that L-Theanine improves sleep. This is likely due to the reductions in feelings of stress.
There is not a massive amount of research, but it looks consistently positive.
Based on the evidence, I would wager it is unlikely to help sleep in those with low stress levels. Considering the majority of people report stress being a factor that affects their sleep though, it makes sense that it consistently helps a large portion of people.
Combining L-Theanine and Caffeine
L-Theanine and caffeine are a common combination that is recommended for those wanting to improve productivity.
Caffeine has well-documented benefits for focus, productivity and cognitive function, amongst other things.
Alongside those benefits, there are some downsides. It can increase feelings of stress and anxiety, increase heart rate, and in some cases increase blood pressure too.
The combination of L-Theanine and caffeine has been shown to improve alertness and cognitive performance while minimising some of the negatives of caffeine.
Of course, L-Theanine does not offset all the other negatives of caffeine, such as the impact on sleep and absorption of certain nutrients.
Are There any Downsides or Side Effects?
L-theanine is one of the safest supplements we have access to.
While long-term data on high doses is limited, some studies suggest that using L-Theanine in typical amounts is unlikely to pose a problem.
One study on rodents used 4,000mg of L-Theanine per kg of body weight per day for 13 weeks, and found no issues. That is an insanely high dosage, so it is reassuring that even with that there were no issues.
There are no common side effects that are reported. Of course, it is always worth double-checking with your doctor, particularly if you are on medications, to see if there are any potential interactions.
Dosage and How to Take
The standard dosage that is the most common recommendation is 200mg per day.
Although going higher appears to be safe, I do not see much reason to go higher at this stage. We see clear benefits from L-Theanine at this dosage. I would only go higher if we start seeing evidence that higher dosages have even more benefits.
It takes L-Theanine 30-50 minutes to peak in the blood. Its half-life ranges from 58 to 74 minutes.
Based on that, it likely makes sense to take L-Theanine ~30 minutes before you want the benefits.
This could be 30 minutes before something stressful, or 30 minutes before bed, for example.
Summary
Although there is not a wealth of research on L-Theanine, the research we have does look promising. There is not much downside to taking it either. If you experience a lot of stress in your life, it is likely worth trialling.
