Could tea, chocolate and apples help lower your blood pressure?
By Christian Heiss, University of Surrey
We're constantly told to "eat healthy", but what does that actually mean? Even doctors sometimes struggle to offer clear, practical advice on which specific foods support health, why they work and what real benefits people can expect.
A growing body of research is starting to offer some answers. Along with colleagues, I have researched whether a group of plant compounds called flavan-3-ols could help lower blood pressure and improve blood vessel function. The results suggest these everyday compounds may have real potential for protecting heart health.
From RTÉ Radio 1's Today with Claire Byrne, Dr Paddy Barrett from Blackrock Clinic on how to reduce your blood pressure
Flavan-3-ols – sometimes called flavanols or catechins – are natural plant compounds that belong to the flavonoid family. They're part of what gives plants their colour and helps protect them from sunlight and pests.
For us, they show up in some of our most familiar foods: cocoa, green and black tea, grapes, apples and even some berries. That slightly tart or bitter note you taste in dark chocolate or strong tea? That's flavan-3-ols at work.
Scientists have long been interested in their health effects. In 2022, the Cosmos trial (Cocoa Supplement and Multivitamin Outcomes Study), which followed over 21,000 people, found that cocoa flavanols, but not multivitamin supplements, reduced deaths from cardiovascular disease by 27%. Our study set out to dig even deeper, focusing specifically on their effects on blood pressure and endothelial function (how well blood vessels dilate and respond to blood flow).
From Irish Heart Foundation, what is blood pressure?
We analysed data from 145 randomised controlled trials involving more than 5,200 participants. These studies tested a range of flavan-3-ol-rich foods and supplements, including cocoa, tea, grapes, apples and isolated compounds like epicatechin, and measured their effects on two key cardiovascular markers: blood pressure and flow-mediated dilation (FMD): a measure of how well the inner lining of blood vessels functions.
The studies ranged from short-term (a single dose) to longer-term interventions lasting weeks or months. On average, participants consumed about 586 mg of flavan-3-ols daily; roughly the amount found in two to three cups of tea, one to two servings of dark chocolate, two tablespoons of cocoa powder, or a couple of apples. Regular consumption of flavan-3-ols led to an average drop in office blood pressure of 2.8 mmHg systolic (the top number) and 2.0 mmHg diastolic (the bottom number).
But for people who started with elevated blood pressure or diagnosed hypertension, the benefits were even greater with reductions of up to 6–7 mmHg systolic and 4 mmHg diastolic. That's comparable to the effects of some prescription blood pressure medications and could significantly lower the risk of heart attacks and strokes.
From HSE Talking Health and Wellbeing podcast, a discussion on hearthHealth with Janis Morrissey from the Irish Heart Foundation
We also found that flavan-3-ols improved endothelial function, with an average 1.7% increase in FMD after sustained intake. This benefit appeared even in participants whose blood pressure was already normal, suggesting these compounds may help protect blood vessels through multiple pathways.
Side effects were uncommon and typically mild, usually limited to minor digestive issues, suggesting that adding flavan-3-ol-rich foods to your diet is generally safe.
Supporting cardiovascular health
While the benefits were most pronounced in those with high blood pressure, even people with normal readings saw improvements in vascular function. This suggests flavan-3-ols may help prevent cardiovascular problems before they begin.
From RTÉ Radio 1's Ray D'Arcy Show, Prof Robert Byrne from the Mater Private Network on how to improve heart health
High blood pressure is one of the major drivers of heart disease worldwide, even at levels that don't qualify as full-blown hypertension (140/90 mmHg or higher). Recent guidelines from the European Society of Cardiology now recognise that even "elevated" blood pressure (120–139 systolic and 70–89 diastolic) carries increased risk.
Lifestyle changes, particularly diet and exercise, are recommended by doctors as first-line strategies. But patients and even healthcare providers often lack clear, specific guidance on which foods truly make a difference. Our findings help fill this gap by showing that boosting flavan-3-ol intake through everyday foods may offer a simple, evidence-based way to support cardiovascular health.
What about supplements?
Some studies tested supplements or isolated flavan-3-ol compounds, but these generally showed smaller effects than whole foods like tea or cocoa. This may be because other beneficial compounds in whole foods work together, enhancing absorption and effectiveness.
At present, it appears both safer and more effective to focus on getting flavan-3-ols from foods rather than high-dose supplements, especially for people taking medications, since interactions are not fully understood.
The studies we reviewed suggest that 500–600 mg of flavan-3-ols daily may be enough to see benefits. You could reach this by combining two to three cups of green or black tea, one to two servings (about 56g) of dark chocolate or two to three tablespoons of cocoa powder, two to three apples, plus other flavan-3-ol-rich fruits like grapes, pears and berries.
Small daily swaps, then, like trading a sugary snack for an apple and a piece of dark chocolate or adding an extra cup of tea, could gradually improve your heart health over time. Because flavan-3-ol content can vary between foods, monitoring your blood pressure at home may help you see if it's making a difference for you.
Combined with other healthy habits, flavan-3-ols may offer a meaningful – and delicious – boost to cardiovascular health
More research is needed, particularly in people with diabetes, where the results were less consistent. We also need to better understand how flavan-3-ols interact with medications and whether even greater benefits can be achieved when combined with other healthy habits.
But the evidence is now strong enough to recommend flavan-3-ol-rich foods as part of a heart-healthy diet. As clinicians seek practical, affordable lifestyle strategies for patients, these findings bring us closer to the idea of using food as medicine.
Of course, flavan-3-ols aren't a magic fix and they won't replace medication for everyone. But combined with other healthy habits, they may offer a meaningful – and delicious – boost to cardiovascular health. And unlike many health fads, this isn't about exotic superfoods or expensive powders. It's about foods many of us already enjoy, used a little more intentionally.
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