THIS is Your Brain on GREEN TEA: New (2025) Science on the Brain Health Benefits of Green Tea *WOW*

Your brain, on green tea, is more focused, less anxious, and way less likely to develop diseases like Alzheimer's, Parkinson's, and Dementia. Those are the findings of a mountain of fascinating new research that has explored how green tea consumption impacts the human brain, and in this video, we are diving into this research and breaking it right down. I began researching this topic formally in 2019 when I published an academic review article about tea-brain interactions, and this article has been cited over a hundred times by researchers around the world. With this endorsement from the scientific community, I thought it was about time to bring this fascinating information to the rest of us, and what better place to do such a thing than the YouTube. We're honing in on two key windows of time in terms of the effects of green tea consumption on the brain. We have the acute effects, which is like the 30 to about 120 minute window of time right after you sip a cup of green tea. These are changes in mood, attention, and cognitive performance. These are coming from caffeine, L-theanine, and some of the other compounds in green tea that we're going to get into in a second. The second window of time is called the chronic effects, and this is how the brain of a green tea drinker looks different through years of daily regular green tea intake, and how such a brain is much less likely to develop diseases like dementia, Alzheimer's, and Parkinson's. For now, let's get into how green tea is impacting the brain. We have our two windows of time, and we have three major green tea molecules, three neuroactive and bioactive compounds in green tea that will be mediating these effects on the human brain. Our first key critical compound is caffeine. Caffeine is the quote-unquote most consumed mind-altering drug on earth. Why is everybody and their mothers dosing up on caffeine throughout the day? Well, acutely, caffeine is improving mood and cognitive performance. It increases attention. People use it as a performance-enhancing drug. Been hitting the gym. It has nothing to do with the gym. You're on drugs. These are the very well-known facts about caffeine intake in the short run, but what is a little bit less known about caffeine is that in the long run, through chronic intake of caffeine, you see significant reductions in risk for Alzheimer's and Parkinson's. Caffeine can actually function as an antioxidant and anti-inflammatory agent in the brain. Moderate, that's the key word here. Too much caffeine is bad, and it affects your sleep latency, actually, your ability to fall asleep, and no benefit of caffeine in the long run can compensate for a loss of sleep or sleep quality. You need to take caffeine in moderation. What is an appropriate amount of caffeine intake daily for humans depends. Humans have a gene called CYP182, and different variants of this gene control your relative ability to degrade and break down caffeine after you've consumed it. If you have a double copy of the slow metabolizer, then you're going to be the person who sips a espresso at 8 in the morning and they still are feeling jittery at 9 p.m. Then you have the fast metabolizers who can drink a cup of green tea and fall asleep 20 minutes later, and then the rest of us are somewhere in between. So it depends on your genetics. It would be nice if you got your genome tested, but you can generally just feel for yourself how much caffeine affects you. Whatever you can drink and not have your sleep affected, that's the right amount for you. Caffeine gets a bad rap, but in reality, if you take it in moderation and you consume it responsibly, it can be pretty good. So the second green tea neuroactive that is mediating these really cool effects on the brain is called L-theanine, and it's this amino acid that has really incredible short-term and long-term effects on the brain. So a really cool review article I found written in 2021 compiled all of the effects that theanine has been found to have on the brain. Some of them were human studies and some of them were animal studies. But you can see we have stress and anxiety relieving effects. We have improved sleep quality. We have alleviation of depression. We have enhanced learning and memory and decreasing risk of neurodegenerative diseases. Study design, different doses of L-theanine, effects, and all these references I have linked in the works cited of this video. Personally, to me, the most interesting of these effects is the anti-stress and anti-anxiety effects. First, because stress and anxiety suck. Hey, Gilmore, you suck. I'd love to punch that guy in the face right now, but I can't, you know, because I'd get in trouble. But secondly, this is the topic that has the most amount of research done about it when you're looking at the effects of green tea and specifically L-theanine on the brain. One of my favorite studies was conducted by Dr. Uno from Japan and she took undergraduate students who were preparing for a final exam and then starting their new job. And so it's a very stressful time in the lives of these students. She had two groups. One was placebo and one was 200 milligrams of L-theanine twice a day. She found during this time, the both subjective and objective markers of stress in these students was significantly lower in the L-theanine group than the placebo group. The subjective stress marker is just asking how stressed out are you right now? And you can rate it 1 to 10. And then the objective marker was measuring the salivary amylase levels. Basically when we're more stressed out, we have more salivary amylase. That study was fascinating, done in humans, subjective and objective measures showing that L-theanine significantly reduced stress in this very stressful time of these students' lives. So there's all types of studies actually just like that that have used human subjects and found that L-theanine had a significant stress reducing and anti-anxiety effect. It's been so clearly observed at this point that researchers are hardly even asking, does L-theanine reduce stress and anxiety? They're more asking, how does L-theanine reduce stress and anxiety? The mechanisms here are actually still an active area of research, but you can check out this article if you want to dive into how this is even humanly possible. For now, let's switch to the chronic side of things. Chronically, through daily regular intake of green tea, you see L-theanine acting again as an antioxidant and anti-inflammatory agent in the brain, which over time contributes to a much lower risk level for Alzheimer's, dementia, and Parkinson's. And indeed, researchers have found a significantly negative correlation between L-theanine intake and risk for Parkinson's disease. And you also see significantly improved cognitive function in middle and older aged individuals. So another effect of regular daily L-theanine intake over time is increased neurogenesis. If you have a human brain cell in a petri dish and you squirt L-theanine on it, then it grows thicker and bigger. It grows more neurites, right? These are the branches of the neuron cell that connect and form connections with other neurons in the brain. So exposed to L-theanine, human brain cells grow, which is pretty incredible. The mechanism is still being worked out, but one article I found by Yoneda showed one potential pathway of L-theanine induced neurogenesis, which you can check out here. And his more recent article is here. These are both working models for how L-theanine works through a number of receptors and signaling molecules to activate neurogenesis in human neurons. A final thing on L-theanine is if you've seen chapter two of the masterclass on tea, you'll remember that L-theanine varies a lot with growing conditions of the tea plant. And it's usually the case that with green tea, it is the more higher grade teas that have more L-theanine levels. If you want to maximize the effects of green tea on the brain, and specifically the L-theanine mediated effects on the brain, then you want to go for the top shelf ----. Now on to our third and probably actually most important neuroactive compound in green tea. That's right, folks. I saved the best for last. We are talking about green tea catechins. Green tea catechins is actually a little family of eight catechins, and the most famous and most abundant in green tea is called EGCG. So what is the function of these green tea catechins in the brain? Well, in the acute time window, you don't see much effect of catechins when it comes to the changes in mood and alertness and cognitive performance in the short run. Green tea catechins are not really the stars of the show. That is more caffeine and L-theanine. However, when we take things long term, when we go chronic, they are doing the lion's share of the work. There's two hugely important ways that these green tea catechins are affecting the brain in the long term. And so the first way is that these green tea catechins are directly acting as free radical scavengers. What is a free radical in the brain? These are basically tiny little asshole molecules that bounce around the cells of your body and destroy things. When they touch the lipids or proteins or DNA of your cells, they rip electrons off of them and make them ineffective. When it happens to your DNA, it can cause mutations that can lead to cancer. But when it happens to proteins and cell membranes, it can cause leakage of things and things just not working properly. Green tea catechins are great at neutralizing these free radicals, making it so that they can't destroy the molecules in your cells. The second big way the green tea catechins are improving brain health and functioning in the brain is green tea catechins are significantly affecting gene expression, the turning on and turning off of key important brain health modulating genes in your brain cells. The first one actually relates back to the antioxidant activity. Something I didn't mention about these free radicals is that aside from being created by toxin exposure, by smoking and drinking and etc. fun activities, they are also created naturally. When we use oxygen to create ATP, we are also generating a small baseline level of free radicals. So basically we've evolved systems inherently in our body to neutralize these free radicals. So we ourselves have our own antioxidant machinery built into our cells and green tea turns up the expression, turns up the genes that create these antioxidant enzymes. One of the most famous ones is called NRF2 and basically exposure to green tea catechins increases the expression of NRF2. That is enhancing our own innate internal capacity for antioxidant function, which I might say is pretty radical. Smacked the lip, tried the barrel and get pitted. You knew the radical pun was coming. So another key gene pathway that's being turned down by green tea catechins is the inflammatory pathway. Green tea catechins are downregulating the expression of inflammation genes. So that is keeping us from getting inflamed chronically, which is great. You mentioned that inflammation is kind of that bridge in between toxin exposure and disease in the long run. It's the exposure to these toxins that creates chronic inflammation and that what a lot of people think is what causes the disease of the brain, such as Alzheimer's, Parkinson's, dementia. So green tea catechins downregulates the inflammation genes and the inflammation response. So the next gene that green tea catechins are changing the levels of and changing the expression of is called CREB. CREB is a really cool gene that upregulates mitochondrial biogenesis, basically increasing the amount of energy and ATP that your brain cells can produce. CREB also turns up the expression of BDNF. And so CREB and BDNF are in one pathway called the CREB-BDNF pathway. And both of those genes are getting activated by green tea catechins and BDNF is huge brain derived neurotrophic factor that induces neurogenesis. That is another thing that's causing the growth in the outbranching of your neurons in your brain. And CREB has also been associated with the healthy normal expression of dopamine and neurotransmitter systems. CREB is going to keep you from bouncing off the walls when you get down some. So basically this profile of gene expression that you get with green tea catechin exposure, we're having more antioxidant activity. We're having less inflammation activity. We're having more CREB-BDNF induced neurogenesis, more growth and outbranching of neurites. And we're having regulated neurotransmission in the brain. You take those and you combine it with the direct free radical neutralizing effects of green tea catechins and you can get a glimpse picture of why a brain that has been consuming green tea for years and years and years looks so different. The architecture of the brain, the physical structure of it, and the biochemistry of that brain is significantly less likely to develop disease. So folks, I wish I could leave the discussion here, right? Because we've covered the three molecules and we've covered the chronic and acute effects, but I simply can't because there's one extra topic within green tea brain effects that is so interesting and maybe could be possibly the most important of everything we've talked about so far. Wow. And it is something called the tea brain gut axis. Research coming out since 2020 in the last couple of years in particular have shown that green tea consumption increases the levels of brain altering bacteria in our gut. There are communities called psychobiotics and green tea enhances, improves the levels of some of these key bacteria like lactobacillus and bifidobacteria that are actually increasing serotonin production and increasing the neurotransmitter levels in your gut and in your brain. And one professor named Zhang Xin from Ningbo University has been leading the charge on uncovering some of these really fascinating ways that tea polyphenols are working through the microbiome to alleviate psychiatric and neurological disorders. His research is honestly mind boggling, or should I say gut boggling and what else boggles my gut? I took all of the information in this video, including the transcript, all of the 104 works cited and 16 of the key figures that you saw flash across the screen and added captions with new information about them. I took all that information, put it into a PDF, which you can download for free using the link in the description. Beyond that, here on YouTube, I have an eight chapter masterclass on tea, which is the ultimate guide to learning about all things tea, including major tea types, tea quality assessment, how to infuse tea properly, global tea history, and more. Chapter one, putting it right there. So check out this video and check out the masterclass as a whole, and I will see you in the next video.