Flavonoid
Research

Plants' defence against stress

Flavonoids are found in all plant-based foods and beverages.

The biggest sources are fruit — particularly apples, citrus and berries — as well as vegetables, tea, red wine and dark chocolate.

"They're compounds that plants produce as a defence mechanism against stress."

"This stress can include things such as UV radiation from the sun or invading pathogens from bugs that land on the plant.

"And so the hypothesis is that they can have a similar protective effect in humans and animals who eat these plants as foods."

But exactly how this protective effect works is unclear.

Dr Bondonno says about 6000 different flavonoid compounds have been identified, along with hundreds of potential actions on the body.

"Clinical trials looking at heart disease have shown that flavonoids can improve the health of blood vessels, decrease blood pressure and they can decrease chronic inflammation," she says.

"There's also been evidence from clinical trials that they can improve blood flow to the brain and improve cognitive function, so how well people perform in mental tests."

Flavonoids can also improve glucose metabolism, and have important implications for diabetes.

"There are many different pathways in the body that can be influenced," says Dr Bondonno.

"The main one though is effects on inflammation and oxidative stress."

Staying out of hospital

Professor Hodgson says flavonoids were originally thought to be acting as antioxidants.

"They're very potent antioxidants in the test tube," he says.

"But research performed over the last 15 or 20 years shows that they don't act as systemic antioxidants in the body.

"So they have a number of other actions which potentially contribute to their health effects.

"In particular, there's consistent evidence that they improve the health and functioning of the arteries."

To find out more, Dr Bondonno has taken the Danish study even further.

She examined hospital admissions for heart disease over the 23-year study period.

Dr Bondonno tracked whether the study participants were admitted for stroke, ischemic heart disease — which causes heart attacks and angina — or peripheral artery disease — a build-up of fat in the arteries of the arms and legs./p>

People with a high flavonoid intake were less likely to be hospitalised for all three types of heart disease.

But the biggest effect was seen for peripheral artery disease.

The research has been enough to make Dr Bondonno think about her own diet.

"I definitely try to eat more fruit," she says..

"I also am happy to have dark chocolate and red wine rather than seeing them as bad things.

"And tea — I try to have a cup of tea a day."