We love a headline that says chocolate is good for us but just how strong is the evidence for a benefit - and does it matter if the research is funded by chocolate manufacturers?
The story so far is that very dark chocolate, but not milk chocolate, has a high concentration of potent antioxidants called flavanols that may have benefits for blood vessels like helping to lower blood pressure a little. One theory is that these flavanols improve the function of the inner lining of blood vessels. This lining produces nitric oxide - and that's important for keeping arteries relaxed and open, making it easier for blood to flow through them.
There's also evidence that dark chocolate may help prevent blood clots, while a recent study from Harvard Medical School in the US found that two cups a day of flavanol-rich cocoa improved blood flow to the brain in older people - but only those whose blood flow was already impaired. It's not the first study to suggest that chocolate is good for older brains - last year Italian researchers reported that giving a high dose flavanol chocolate drink to elderly people with mild cognitive impairment also improved memory.
Another brownie point for chocolate is that it's not considered an artery clogger.
"While chocolate is high in fat, the types of fat it contains are thought to have a neutral effect on blood cholesterol levels, " says Associate Professor Tim Crowe of Deakin University's School of Exercise and Nutrition Sciences.
Promising as this sounds, 'eat more dark chocolate' is unlikely to appear in our Dietary Guidelines any time soon. Not only do the links between dark chocolate and blood vessels need more research, but there's much stronger evidence that other things like regular exercise and a high intake of vegetables and fruit do a better job of keeping arteries and blood pressure healthy.
If you want chocolate for its health benefits, the bottom line is this: you need the dark stuff containing 70 to 85 per cent cacao - that's different to the chocolate bars that fill most supermarket and dairy shelves.
And you only need a little.
"One row of dark chocolate two or three times a week is enough,' says Crowe, adding that you could scrape by on even less - just one square a day has been found to have benefits. "Chocolate is one of the most kilojoule dense foods that we eat - a 100 gram block has 2240 kilojoules - more than a quarter of the kilojoule needs of an average adult."
Dark chocolate isn't the only way to get flavanols into your diet either - tea, grapes and apples are other rich sources, though they might not make the same compelling headlines.
Much of the research into chocolate has been funded by chocolate manufacturers but this doesn't mean the results aren't to be trusted, Crowe says.
"It's just that the industry is more likely to fund research that is likely to give positive results and some researchers may be prevented from publishing research that gives a negative finding."
Earlier this year an Australian study from Swinburne University set out to see if a daily chocolate drink enriched with flavanols improved mood or cognition - and although it didn't help with mental sharpness, it did enhance mood, says Professor Con Stough of Swinburne University's Centre for Human Psychopharmacology.
But while chocolate might look promising in studies using a specific dose of flavanols, there's no guarantee that a chocolate bar from the supermarket contains a high level of these antioxidants because they can be destroyed during the manufacturing process, he says.
"There's a good chance that there's not much in there - but the chocolate will still taste good."
- Sydney Morning Herald
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