Researchers have published a list of 20 functional foods that promote healthy living and could extend longevity – with coffee and dark chocolate featured alongside more traditional ‘healthy’ fruit and vegetables.

Gary Williamson, a professor of functional food at Leeds University, has recommended a list of 20 “lifespan-essential” foods containing polyphenols, whose antioxidant properties are said to help battle cancer and heart disease.

Fruit and vegetables comprise the majority of the list, although coffee and black tea join more traditional superfoods such as broccoli, blueberries and spinach. Dark chocolate also makes an appearance on the list.

“These foods have been chosen because they are highest in polyphenols, which reduce the risk of heart disease and help to slow down ageing processes,” Williamson told the Daily Mail.

“A low intake of fruit and vegetables increases the risk of chronic disease, whereas the foods on this list maximise one's chances of reaching your potential lifespan, which is why I call them ‘lifespan-essential’.”

But “they're not going to enable you to live to 200,” he cautioned.