The secret is revealed to be naturally occurring substances in chocolate that may offer some degree of protection against heart disease and related circulatory disorders.
Many studies have shown that food rich in flavonals, found in plant-based foods such as apples, onions, peanuts and cranberries as well as in red wine and chocolate, can help to maintain cardiovascular health.
Now evidence is accumulating that chocolate is particularly rich in larger flavonoid molecules, the complex oligomers. It also appears to have a higher anti-oxidant activity than red wine - a study at King's College London found that 50g of dark chocolate contains as many flavonoids as six apples, two glasses of wine or seven onions.
Chocolate as an ancient medicine
Recognition of cocoa's health properties is nothing new. As far back as the 16th-century Spanish priests were aware of the nutritional properties of the highly prized Mayan cocoa drink and sanctioned its use as a food substitute during periods of fasting.
According to American scientists speaking at the National Academy of Sciences in 2004, cocoa seems to keep down the blood pressure levels of the Kuna Indians off the coast of Panama who eat lots of locally grown cocoa that is high in flavonoids.
However, when city-dwelling Kuna change to processed cocoa products the benefit is lessened, leading researchers to introduce chocolate that retains more of the health-boosting chemicals that help your heart.
So until nutriceutical versions of flavonoid-enhanced chocolate are on the market your healthiest option is dark chocolate with at least 70 per cent cocoa.
Chocolate slows blood clotting
In a study by the University of California, volunteers ate either 25 g of semi-sweet chocolate, manufactured by Mars, while a control group had bread.
Blood samples were taken from both groups before they ate and again two and six hours afterwards and their platelet function was measured. Platelets are tiny cells in the blood, which help it clot if there is an injury. In this study, researchers looked at how long it took platelets to fully close an opening and found it took significantly longer in people who had eaten chocolate.
Professor Carl Keen, of the University of California, Davis, told the British Association for the Advancement of Science last year that eating small amounts of chocolate could have the same anti-clotting effect as taking an aspirin and so might reduce the risk of deep vein thrombosis when flying.
Chocolate cuts 'bad' cholesterol
Another study, at Penn State University, compared a diet low in flavonoids with one high in chocolate and found that people who ate lots of chocolate had higher anti-oxidant levels in their blood and lower levels of LDL-cholesterol - the type that is implicated in hardening of the arteries. Further research also found that a diet supplemented with chocolate reduced LDL levels.
Finally, scientists in Switzerland found that volunteers who ate chocolate laced with calcium absorbed 13 per cent less chocolate-derived fat and nine per cent fewer calories than those who ate chocolate on its own.
Find out more about cholesterol
Chocolate boosts antibodies
You don't even have to eat chocolate to benefit from it. At the University of Westminster, Dr Angela Clow found that just sniffing chocolate can give the immune system a boost.
In the study volunteers sniffed chocolate, rotting meat and water. When chocolate was sniffed their antibody levels in increased.
Further proof that some of the enjoyable things in life can keep us healthy, while stressful or depressing situations can make us more open to infection.
How to boost your immune system
Chocolate as an artery aid
A study reported in New York to the American Society of Hypertension meeting showed that volunteers had less arterial stiffness after consuming 100g of good quality, plain chocolate. Dr Naomi Fisher, of Brigham and Women's Hospital in Boston, USA, believes that the flavonoids in cocoa act on an enzyme in the body called nitric oxide synthase, which helps the cocoa to dilate blood vessels, improve kidney function and lower blood pressure.
In addition, Greek scientists reporting at the European Society of Cardiology conference in Berlin in 2004 said that in their study of 17 healthy young volunteers functioning of endothelial cells, which control the degree of stiffness in the blood vessels, was improved for three hours after eating dark chocolate.
Find out more about blood pressure
Chocolate as a cough cure
Research from Imperial College London says that theobromine, a key ingredient in chocolate, is a third more effective than codeine when it comes to clearing up a cough.
According to the online FASEB Journal, the team induced coughing in 10 healthy volunteers with capsaicin from chilli peppers, and then measured how much was needed to produce a cough after they had been dosed with theobromine, codeine or a placebo.
In comparison with the placebo, when the volunteers had taken theobromine they needed around a third more capsaicin to produce a cough, whereas they needed only marginally higher levels of capsaicin after taking codeine.
Theobromine works by suppressing the activity of the vagus nerve, which causes coughing and, best of all, it doesn't produce any adverse effects on the cardiovascular or central nervous systems.
Professor Maria Belvisi, one of the study's authors commented: "Normally the effectiveness of any treatment is limited by the dosage you can give someone. With theobromine having no demonstrated side effects in this study it may be possible to give far bigger doses, further increasing its effectiveness.
"At the same time, theobromine may not have any of the side effects such as drowsiness. This means there will be no restrictions on when it can be taken. For example, people using heavy machinery or who are driving should not take codeine, but they could take theobromine."
So although it's not possible to clear a cough with chocolate, there may be a role one day for a medicine based on a chocolate extract.
Find out more about how to treat a cough
For the love of chocolate
Romances are often sealed with a box of chocs and there may be a good reason for this. Chocolate contains the natural love drug tryptophan.
The brain uses this to make a neurotransmitter called serotonin and usually the more serotonin you have, the happier you feel.
In addition, chocolate contains small quantities of phenylethylamine, another neurotransmitter that creates feelings of giddiness, attraction and excitement in the brain's pleasure centre - levels peak during orgasm.
Discover more mood boosters
Chocolate and weight gain
Of course, eating too much chocolate can pile on the pounds - a small bar contains about a quarter of the recommended daily calorie intake for women. What's more, chocolate contains saturated fats, the ones closely associated with heart disease.
If you're watching your weight, it's worth knowing that a survey of people's dieting habits for Marks and Spencer revealed that chocolate derailed the best intentions of 48 per cent of female dieters and 32 per cent of male dieters.
To indulge your chocolate habit without regrets, choose dark varieties containing at least 70 per cent cocoa solids and check that they contain low levels of cocoa butter.
And try to make a little go a long way: the researchers who've studied the subject say you get maximum benefit with fewer ill effects from just one or two squares a day.
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