The amino acid L-theanine is said to promote concentration, calm down and thus even improve sleep without making you tired. And it works best with caffeine. But isn’t all this contradictory? FITBOOK explains what the substance is all about and what it contains.
A natural active ingredient that promises more mental performance, but still ensures that you stay relaxed – and without any side effects? What sounds like the perfect remedy for our sometimes hectic everyday life actually exists: L-theanine. The amino acid is mainly found in real tea (Camellia sinensis), with green tea having a slightly higher proportion than black tea.
The Effects of L-Theanine
Scientists have found that the L-theanine in tea acts as a sort of antagonist to caffeine. Because caffeine not only wakes you up, but also has unpleasant side effects. Especially in higher doses, it can lead to tachycardia, inner restlessness, insomnia and increased blood pressure. This is where L-theanine comes into play, as it is said to be able to neutralize the negative effects of caffeine. What happens is the often-described effect of green tea: it gently wakes you up – not as stimulating as coffee, but long-lasting – and relaxes you at the same time.
As early as 1999, a study by the University of Shizuoka in Japan showed that L-theanine stimulates the so-called alpha waves in the brain.1 This causes relaxation without causing sleepiness. The scientists determined that L-theanine and thus the consumption of green tea lead to a reduction in stress. They also reported on earlier animal studies on rats that had shown that L-theanine also had a positive effect on the animals’ learning performance and memory. Another study from Japan in 2006 confirmed the relaxing effect of L-theanine on people.2 Tests on rats also showed that the substance has a blood pressure-lowering effect.3
The industry is trying to potentiate the effects of L-Theanine and sell it in dietary supplements. Because what works well in tea should be reinforced with an artificially high-dose drink or snack – at least that’s the theory.
Green tea contains a particularly large amount of L-theanine, which reduces stress and at the same time promotes concentrationPhoto: Getty Images
What does the Federal Office for Risk Assessment say about L-theanine?
Although L-theanine is considered harmless in naturally occurring amounts such as in tea, the Federal Office for Risk Assessment (BfR) believes that the risk of negative effects on the ability to react and alertness in the case of very high artificially administered doses has not been sufficiently clarified. For this reason, the use of artificially added L-theanine in drinks is not permitted in Germany.
«Due to the fact that too little is known about the desired and undesired effects of isolated L-theanine in the human organism, the BfR rejects the addition of isolated L-theanine in beverages,» says an assessment from 2003.4
What is amazing, however, is the fact that isolated L-theanine is freely available as a powder and that anyone can use it to enrich their own drinks and other foods. It is also often sold in capsule form.
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The assessment of the US authorities
The US Food and Drug Administration (FDA) has few concerns and awarded L-theanine the rating “harmless to health” back in 2007.
According to their study evaluation, the FDA assumes that 250 milligrams of L-theanine per serving can be taken in drinks and food without hesitation. That would roughly correspond to what a normal tea drinker consumes per day. According to the FDA, a heavy tea drinker can consume up to 825 milligrams of L-theanine per day. This value is therefore also classified as harmless.
You can generally save on powder or capsules with the active ingredient: if you want to relax but also want to be mentally fit, you can simply drink black and green tea more often. It also contains many other valuable ingredients such as antioxidants.
Sources
- 1. Lekh Raj Juneja, Djong-Chi Chu, Tsutomu Okubo, Yukiko Nagato, Hidehiko Yokogoshi.
L-theanine – a unique amino acid of green tea and its relaxation effect in humans.
Trends in Food Science & Technology, Volume 10, Issues 6–7 (1999) - 2. Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biol Psychol. 2007 Jan;74(1):39-45. doi: 10.1016/j.biopsycho.2006.06.006. Epub 2006 Aug 22. PMID: 16930802.
- 3. Hidehiko Yokogoshi, Yukiko Kato, Yuko M Sagesaka, Takanobu Takihara-Matsuura, Takami Kakuda, Naokazu Takeuchi, Reduction Effect of Theanine on Blood Pressure and Brain 5-Hydroxyindoles in Spontaneously Hypertensive Rats, Bioscience, Biotechnology, and Biochemistry, Volume 59, Issue 4, 1 January 1995, Pages 615-618, https://doi.org/10.1271/bbb.59.615
- 4. Federal Office for Risk Assessment. Statement of the BgVV updated by the BfR in August 2003 (retrieved on June 23, 2021)