Decoding How Flavonoids Boost Brainpower
This Week’s Research Highlight
From Garden to Gray Matter
We’ve long known that eating colorful fruits and vegetables is good for our health — with beneficial effects ranging from our metabolism to the cardiovascular system.
But emerging science suggests that these plant-derived pigments, called flavonoids, may also enhance cognition. And these cognitive advantages seem to become even more important as we get older.
Flavonoids work their mental magic through multiple pathways. In the short term, they improve blood flow to the brain, leading to quick boosts in mental performance which usually peak around two hours after consumption. However, the long-term effects are even more intriguing. When consumed regularly over weeks or months, flavonoids trigger lasting changes in brain function.
One thing that makes these plant compounds special is their size — they're small enough to cross the blood-brain barrier, a selective gateway that keeps many substances out of our brain tissue. This has been demonstrated dramatically in animal studies: when rats consume blueberries for ten weeks, scientists can actually find berry compounds distributed throughout their brain tissue!
Researchers have been trying to puzzle out the cellular and molecular mechanisms that underlie these cognitive improvements. The answer might lie in brain-derived neurotrophic factor (BDNF) — a molecular "fertilizer" for your brain that helps strengthen connections between neurons, supports the formation of new ones, and keeps your hippocampus (the brain’s memory hub) running smoothly. In essence, BDNF is what allows you to think, learn, and remember.
To gain more insight into how dietary flavonoids influence BDNF — and in turn, cognitive performance — researchers at the University of Reading in the UK conducted two different trials, each tackling the question through slightly different approaches.
Trial 1: Fruit and Vegetable Study
The first trial enrolled 154 participants aged 26-70 years, who typically consumed about 3 portions of fruits and vegetables daily.
The researchers divided participants into three groups:
- High-flavonoid fruit and vegetable group (>15 mg of flavonoids per 100 g of food)
- Low-flavonoid fruit and vegetable group (<5 mg of flavonoids per 100 g of food)
- Control group (maintaining usual diet)
The high-flavonoid group received foods known to be rich in these compounds, while the low-flavonoid group received alternative fruits and vegetables that were otherwise matched in terms of other nutrients like vitamins, minerals, and fiber. This helped ensure that any differences observed could be attributed specifically to flavonoid content, rather than other nutritional factors.
To facilitate participant compliance, the research team provided all fruits and vegetables to participants' homes weekly.
Trial 2: Cocoa Flavanol Study
In contrast, the second study focused on supplementary intake of flavonoids from a single source — highly concentrated cocoa. Cocoa is unique because it is extremely high in flavanols, a subclass of flavonoid.
Forty healthy older adults (aged 62-75 years) were randomly assigned to one of two different cocoa drinks — one high in flavanols (494 mg) and one low in flavanols (23 mg). The drinks were carefully formulated to match in taste, appearance, and nutrient content (including caffeine), differing only in their flavanol levels.
So, instead of getting a broad mixture of flavonoids from whole foods, like in the first trial, participants in the second trial consumed a single class of flavonoids (flavanols) in a highly concentrated form that would be nearly impossible to achieve through diet alone.
To put the comparative dosing into perspective here, the high-flavonoid group in the first trial achieved an intake of 198 mg per day of total flavonoids, which included 27 mg of flavanols. Meanwhile, the cocoa flavanol supplement group was getting 494 mg of flavanols in a single daily dose.
Measuring Effects on Brainpower
In order to measure the biochemical effects of both interventions, the researchers collected blood samples to measure BDNF levels throughout the studies.
Furthermore, the team used a comprehensive battery of cognitive tests to assess various aspects of brain function. These tests evaluated:
- Executive function
- Working memory
- Episodic memory
- Spatial memory
- Processing speed and attention
What They Found
Before either of the interventions even began, the researchers noticed something important — participants who started out with higher BDNF levels performed better, on average, on their baseline cognitive tests.
This suggests, as you might suspect, that serum BDNF levels could be a useful indicator of individual cognitive function, and also lends further support to its use as a relevant biomarker for this study specifically.
Participants with the highest baseline levels of BDNF (above 300 pg/ml) consistently showed better cognitive performance compared to those with lower levels.
As far as the interventions, let's start with the fruit and vegetable trial.
After 6 weeks, the participants consuming high-flavonoid fruits and vegetables began showing significant increases in BDNF levels, which became even more pronounced at the 18 week mark.
And if we look at their cognitive function scores, we can see that the rise in serum BDNF was closely followed by improvements in brainpower.
Meanwhile, the low-flavonoid group, despite eating the same amount of additional fruits and vegetables, didn't show similar improvements.
This tells us that it's not just about eating more fruits and veg, or even increasing intake of nutrients — the flavonoid content specifically is what matters.
The results from the cocoa trial were quite similar. When participants consumed the high-flavanol cocoa drink, their BDNF levels increased significantly. And the rise in growth factors was associated with an improvement in global cognitive scores.
The Best of Both Worlds
So which is better: diverse flavonoids from whole foods, or concentrated cocoa flavanols?
Let’s start with the whole fruit and vegetable approach. One major advantage is the variety of flavonoids it offers. Each flavonoid subclass—such as flavanols, anthocyanidins, or flavonols—has a unique chemical structure and interacts with our bodies in distinct ways. When consumed together, these compounds may even have synergistic effects, amplifying their health benefits. This is one reason why nutritionists encourage us to "eat the rainbow" — a diverse diet ensures we reap the full spectrum of phytochemicals and their associated advantages.
Diagram from Linus Pauling Institute
For example, if we look back at the list of assigned foods in the study, participants would have gotten flavanols from apples and grapes, anthocyanidins from berries, flavonols from leafy greens, flavanones from citrus fruits, and flavones from peppers. Each food could contribute a unique piece to the puzzle of cognitive health.
On the other hand, cocoa is a concentrated source of one specific flavonoid subclass, which is notable for its ability to cross the blood-brain barrier and directly influence cognitive function. While this approach doesn’t provide diversity, it delivers a potent dose of a compound with well-documented effects on brain health — almost like a targeted intervention.
For instance, when researchers at Columbia University Medical Center had healthy older adults consume a high cocoa flavanol drink (very similar to this trial), they showed improvements in memory tests equivalent to turning back the clock three decades. According to senior author Scott Small, "If a participant had the memory of a typical 60-year-old at the beginning of the study, after three months that person on average had the memory of a typical 30- or 40-year-old."
The bottom line? Both approaches can work. Each led to significant improvements in cognitive performance and increases in BDNF levels. The practical takeaway is that these strategies don’t have to compete — they can complement each other. Just as we combine general fitness routines with targeted training for specific goals, we can integrate a diverse intake of flavonoid-rich foods into our daily diets while using concentrated sources like cocoa for an extra boost.
What’s clear is that flavonoids, whether from whole foods or concentrated sources, are a powerful tool for brain health. These plant compounds, originally evolved to protect their parent species, have become invaluable allies in our quest for better cognitive function.
Random Trivia & Weird News
An Italian grandmother nearly killed her family (inadvertently) by serving them 25-year-old hot chocolate.
Back in 2015, a well-meaning Italian nonna served hot cocoa from packets that had been quietly aging since 1990.
The family gathering turned into an impromptu emergency room visit, with three children, an adult guest, and finally the grandmother herself succumbing to the ancient mix. Police, apparently not swayed by the "it was still good!" defense, charged her with causing injury through neglect.
The local newspaper reminded readers exactly how old the cocoa was by referencing Italy's crushing World Cup defeat to Argentina that same year — because in Italy, even food poisoning stories need a soccer reference.
Podcasts We Loved This Week
- Joe Klemczewski & Eric Helms: Are we doomed? Trust, misinformation, and the future of health & fitness science. Via Sigma Nutrition Radio.
- Vivek Murthy: Surgeon General highlights link between alcohol and cancer. Via Science Friday.
Products We Like
CocoaVia
Getting therapeutic doses from regular dark chocolate or cocoa powder presents some challenges. Processing methods like alkalization (dutching) can significantly reduce flavanol levels. And most commercial chocolate products just don’t contain a whole lot of flavanols.
To put it into perspective: A typical 100g bar of dark chocolate (70-85% cocoa) contains somewhere between 100-200mg of flavanols. So to get 494mg of flavanols just from dark chocolate, you'd need to eat around 2.5-5 bars of dark chocolate — that's like 1000-2000 calories just from chocolate! Clearly, this wouldn't be a practical or healthy way to achieve this intake.
Each scoop of the powder contains 500 mg of cocoa flavanols — almost exactly the amount tested in clinical research, including today’s feature study. They also offer capsules but the powder is more cost-effective, and it’s not hard to use.
humanOS Catalog Feature of the Week
Neurotrophic Factors and Blood Flow — from Nutrients for Thinking
In this lesson, we cover:
- How flavonoids overcome the blood-brain barrier challenge that plagues many pharmaceutical compounds
- The story of fisetin, a strawberry-derived flavonoid being studied at the Salk Institute
- Why the brain, despite being only 2-4% of body mass, requires 20% of our blood supply
- The surprisingly rapid cognitive benefits observed in both children and adults after consuming flavonoid-rich foods
This lesson is part of our Daily Performance & Diet course, which explores how dietary choices affect cognitive function, energy levels, and long-term brain health.
Ready to dive deeper into the science of brain-boosting foods?
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- Scroll down to find DP Diet - 05 - Neurotrophic Factors and Blood Flow
Wishing you the best,
