Monday, July 24, 2017

How Does Tea Affect the Brain?

As many of you know I'm pretty strict about not covering health benefits here on the blog. They aren't why I drink tea and in most cases, I think they are overemphasized for marketing purposes. That being said it is undeniable that tea does affect our bodies in many ways. I thought it might be interesting to dive a little deeper into what substances in tea have an effect on the human brain.


Caffeine is one of the most widely used psychoactive substances in the world. It naturally occurs in tea and is partially responsible for the bitter taste that we experience. Caffeine is structurally similar to adenosine, a neurotransmitter that plays an important role in regulating sleep cycles. Adenosine is built up over the course of the day which eventually triggers our body to rest. Caffeine binds to adenosine receptor sites in the brain so that rather than slowing down we feel energized.

Luckily for us, this effect is not a permanent one. If the adenosine receptors are blocked the body will create new ones. Just as with many other drugs, this is why people can become addicted to caffeine. The body demands more and more of the substance in order to achieve the desired effect. It is also why we might experience withdrawal symptoms if our brains are deprived of caffeine. This seems to be less of a problem in tea circles than it is with the coffee crowd but it's still important to make sure that we don't overdo it. According to the Mayo Clinic, a healthy adult can safely consume up to 400mg of caffeine per day.


L-Theanine is an amino acid found in tea which relaxes the central nervous system and promotes alpha brain wave activity. This can lower anxiety and help us to feel more relaxed. It also increases the levels of dopamine and GABA in the brain. Given what we now know, it isn't so surprising that tea has been so intimately associated with zen and meditation throughout its history.

Some studies have found that L-Theanine is even more effective when it is combined with caffeine (aka tea!) than when it is taken on its own. Shade grown teas such as matcha and gyokuro contain higher levels. L-Theanine is a substance that is almost exclusively found in the Camellia Sinensis. Scientists have only found it in two other sources, guayusa and a species of mushroom.


EGCG, or epigallocatechin gallate, is a polyphenol that receives a lot of the attention when it comes to studies on the health benefits of tea. Although conclusive studies are still needed, some studies have found that EGCG has the potential to prevent oxidative damage to brain cells, increase neurogenesis, and improve working memory. It's important to note that the FDA does not allow health claims to made about tea. Retailers can reference studies but the wording must be very careful in order to avoid legal hot water.



GABA, or gamma-Aminobutyric acid, is a neurotransmitter that plays a role in reducing excitability in the central nervous system. It is naturally found in tea in low levels but the amount can be increased by essentially making the tea in a vacuum. The leaves are exposed to a nitrogen rich environment during the oxidation step. This process was originally developed in Japan as a natural method for preserving food. Teas that are labeled as GABA should contain at least 150mg per 100g of leaves. Although I can't say that I've noticed any benefits from drinking GABA tea, they have a unique fruity taste that is worth exploring.

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EGCG chemical structure image: Public Domain, Link