Green Tea: Brain Tonic or Just Hot Water Salad? A Look at What the Science Says

Green tea has been around forever, literally thousands of years, and people swear by its benefits. Now, with green tea hitting the mainstream in the West, everyone wants to know if this stuff is actually doing anything for our brains. Luckily, a systematic review (Mancini et al. 2017) has dug into the scientific literature to find out if green tea, its extracts, or key components like L-theanine and EGCG actually impact our cognition, mood, and brain function. They sifted through studies conducted on humans, looking for interventions with green tea compounds and outcomes related to the brain or neuropsychology. They ended up reviewing 21 studies, and overall, the quality of these studies was assessed as good.

The Bottom Line: Yes, There’s Something There

The headline? The studies reviewed offer evidence that green tea does influence psychopathological symptoms, cognition, and brain function. Think reducing anxiety, improving memory and attention, and even showing up as activation in brain areas associated with working memory in fancy functional MRI scans. So, it’s not just placebo or ancient folklore; there’s a biological angle here.

It’s Not Just One Magic Molecule

Here’s where it gets a bit more nuanced, and frankly, less sexy for the supplement peddlers. The review highlights that the beneficial effects of green tea can’t be pinned down to just one ingredient. This is a key takeaway. For example, when it comes to improving cognition, the studies suggest that the benefits are most notable when you get the combined punch of both caffeine and L-theanine, two major components found in green tea. Giving people just caffeine or just L-theanine seemed to have less impact on cognition compared to the dynamic duo together. This suggests a synergistic effect, meaning they work better as a team.

Diving Into the Components

Let’s break down what the review found for the individual players and the tea itself:

•Green Tea and Green Tea Extract (GTE): Short-term, GTE showed improvements in memory and attention, and brain imaging (fMRI) indicated increased activation in areas crucial for working memory. One study using fMRI specifically found that green tea enhanced connectivity between brain regions during working memory tasks, leading to improved performance. Long-term, habitual green tea consumption was linked to a lower risk of functional disability and cognitive impairment in older folks, with benefits increasing with the amount consumed (up to about 500 ml per day). It was also associated with better performance on a range of cognitive tests in older adults.

•EGCG: This polyphenol, epigallocatechin gallate, is abundant in green tea. Studies found that EGCG intake had a calming effect and relieved stress, showing increased overall activity in certain brain wave frequencies (alpha, beta, theta) in EEG scans, linked to frontal brain regions. While some studies showed reduced cerebral blood flow in the frontal cortex with EGCG, cognitive improvements from EGCG alone were primarily noted in specific patient populations, such as improved visual memory recognition in individuals with Down’s syndrome.

•L-Theanine: This amino acid is another key green tea component. Alone, L-theanine showed some benefits in reducing stress and anxiety in short-term studies. However, findings on its standalone cognitive effects were mixed, with one study even reporting headaches and worse performance on a cognitive task. Long-term use of L-theanine as an add-on therapy benefited patients with schizophrenia or schizoaffective disorder by reducing positive symptoms and anxiety, though cognitive improvements weren’t found in this group.

The Caffeine Connection

The review strongly emphasizes the role of L-theanine when combined with caffeine. This pairing consistently showed beneficial short-term cognitive effects across several studies, including enhanced attention, faster reaction times, and improved memory. Volunteers also reported feeling more alert and less tired with this combination. These effects often surpassed those seen with either L-theanine or caffeine administered on their own, reinforcing the idea of synergy.

Limitations and What We Don’t Know

Before you start mainlining green tea, the review points out some important caveats. The studies were quite varied, making it impossible to just crunch all the data together in a meta-analysis. Pinpointing the exact minimal effective dose or duration for achieving consistent benefits, either acute or chronic, remains unclear from the reviewed literature. Also, focusing just on EGCG and L-theanine means we’re not accounting for potentially relevant effects or interactions of other compounds in green tea.

The Takeaway for Your Brain

So, what’s the actionable intelligence here? Based on this review, including habitual, daily green tea consumption of at least 100 ml per day in your lifestyle appears desirable for protecting your neurocognitive function, particularly as you age. While the specific mechanisms are still being teased out, and more research is certainly needed on optimal doses, long-term effects, and how the various compounds interact, the evidence suggests there’s real potential for green tea to offer tangible benefits for your brain and mood. Just don’t expect a single EGCG pill to solve all your problems; the power seems to be in the blend, especially the L-theanine and caffeine working together.

Source Reviewed:

Mancini, E., Beglinger, C., Drewe, J., Zanchi, D., Lang, U. E., & Borgwardt, S. (2017). Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine, 34, 26-37. https://doi.org/10.1016/j.phymed.2017.07.008