Chocolate: decadent, delicious... and good for your brain?

Two human studies add to the evidence that flavanols are brain-boosters. Belinda Smith reports.

As if we needed another reason to eat chocolate – two studies show that flavanols, a compound found in cocoa, reverse age-related memory loss.

A study led by Adam Brickman from Columbia University in New York and published in Nature Neuroscience found a high-flavanol diet enhanced blood flow to a memory-forming part of the brain. Not too long after, Daniela Mastroiacovo from the University of L’Aquila in Italy's Abruzzo region reported in the American Journal of Clinical Nutrition that seniors who were fed hefty daily doses of flavanols performed better on cognitive tests after only eight weeks.

“Both of these studies add to the growing body of literature that suggests high flavanol exposure will reduce memory decline and even seems to improve memory over time,” says Ian Musgrave, a molecular pharmacologist at the University of Adelaide.

You need to eat at least a couple of blocks of good quality dark chocolate a day to receive the benefits from the flavanols in the cocoa. – iStock

But before you race for the chocolate, there’s a rub. You’d need to eat at least a couple of blocks of good quality dark chocolate a day to get the effective dose of flavanols – and there’s almost none in milk chocolate. That's definitely not good for the waistline or one's general health. Instead the participants in both of these studies were given flavanols in specially designed tablets and drinks.

Brickman gave 37 volunteers aged 50-69 years either a high dose of flavanols (900mg) or a low dose (10mg) each day for three months. The two groups then had an MRI scan to measure the blood flow to the dentate gyrus – a key region for memory formation whose function usually declines with age. In those on the high-flavanol diet, the dentate gyrus was receiving a greater blood supply.

They also compared memory tests taken before and after the three-month treatment period and found those taking high doses of flavanols had memory improvements too.

Beyond mental improvements, the study also found the subjects’ health had generally improved.

Beyond mental improvements, the study also found the subjects’ health had generally improved.

“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,” says Scott Small, a neurologist at Columbia University Medical Centre and senior author of the study.

Mastroiacovo built on these results in her study and gave 30 volunteers aged 61-85 years a drink containing 993mg of cocoa flavanols every day for eight weeks. Comparable groups received a drink with 520mg or 48mg of the supplement.

To test their subjects’ mental muscle, the researchers plied them with tests that measured attention and recall, the ability to follow commands, language skills and the overall speed of their performance. Subjects were ruled out before the experiment started if they showed any clear signs of disorientation or memory loss.

Those on the high-flavanol diet outperformed the controls in tests of verbal fluency and processing speed. And consistent with what had been found in the former study, they also found the subjects’ health had generally improved – their blood pressure and insulin resistance were lowered.

So how do flavanols improve cognitive function? The brain relies on a dense network of blood vessels to supply it with oxygen, glucose and other nutrients, and to carry away waste. If that network is healthier, the brain is able to work more efficiently. While not fully understood, “cocoa flavanols can have profound effects on [the performance of blood vessels], and we now know, specifically within the brain,” says senior author Giovambattista Desideri, director of the Geriatric Division at the University of L’Aquila.

But although these studies add to the growing body of research on the benefits of flavanols, not everyone is convinced seniors should be dosing themselves with high levels of the stuff.

It’s promising to see benefits after only a couple of months, Musgrave says. But he points out that medical research is littered with examples such as memory improvement after taking ginkgo biloba where beneficial effects seen in small groups “disappear like snow in the sun” when tested more broadly.

Not all scientists are convinced that the cocoa bean, above, will deliver benefits to the ageing brain. They say larger studies need to be done. – iStock

Brickman’s study also had a small sample size – only 37 people in total – and, Musgrave points out, those memory results were barely statistically significant. “Perhaps the subjects in that small group responded particularly well by chance alone,” he says.

So rather than “everyone buying flavanol tablets and scarfing them down by the handful,” Musgrave says, we first need to carefully look at their effects in the wider population over a longer period – something that, Desideri says, is on the cards: “It is likely that in the future we could propose evidence-based nutritional interventions based on regular cocoa flavanol consumption to support healthy ageing. [But] for now we’d like to know how they work and how long the effects last.”

“If we can establish those effects,” Musgrave says, “it would be really exciting.”

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