A chocolate bar prescribed on the NHS? It sounds too ridiculous even for Roald Dahl's hero. But it could be the future of confectionery

But while Roald Dahl imagined a time in which sweets could be transported by television and a three-course meal would be reduced to a strip of chewing gum, even his creative mind missed one potential innovation - an NHS-prescribed medicinal bar of chocolate that cuts heart disease and lengthens life expectancy.

The chocolate industry, threatened with Government curbs on advertising, falling profits and demonised by parents and nutritionists for fuelling the obesity epidemic, is trying to shed its unhealthy image and convince a sceptical public it can help the drive for a better diet.

Confectionery companies are spending millions of pounds on research to prove the benefits of the cocoa bean, and develo, "healthy" products that could be as useful as drugs in treating heart disease and other conditions.

The Masterfoods group, which makes Mars bars among other things, may not have an army of Oompa-Loompas but it has recently spent a substantial part of the profits from its $18bn of global sales on setting up the "Mars Nutrition for Health and Wellbeing Business Unit".

A team of researchers was charged with coming up with a nutraceutical - a food that has medicinal properties and could have the power to transform the confectionery market.

The health benefits of chocolate have long been known - it was used in the 16th century to raise stamina and prevent disease, while Indian homeopaths blended preparations of the cacao fruit to treat low blood pressure.

Cocoa , from which chocolate is made, are among the best sources of chemicals called flavenols and phytosterols which are good for the heart.

Flavenols are anti-oxidants present in fruit, vegetables, tea and red wine which prevent damage to the cells from normal metabolism, and phytosterols lower cholesterol. In normal processing to make ordinary chocolate, most of the flavenols are destroyed, and the addition of refined sugar and fat makes the finished product high in calories and low in health benefits.

But the Mars team developed a process that preserves the "healthy" chemicals.

The result is a chocolate bar called CocoaVia, which contains just 80 calories and high levels of flavenols.

According to the company's website, www.cocoavia.com, the bars are so revolutionary that "one taste and you'll wonder how anything so tasty can be so good for your heart health".

It advises consumers to eat two bars a day to ensure they reap all the health benefits. The chocolate bars are currently only available in the US by mail order and sell for $1(50p) each.

Masterfoods has also developed a cocoa drink based on CocoVia, to be taken as a small dose each day. A British research team, which asked to test it, found it reduced the risk of blood clots and could be used to prevent heart disease and strokes.

The 85ml drink was taken once a day and blood tests on 16 patients showed reduced "stickiness" of the platelets.

Denise O'Shaughnessy, consultant haematologist at Southampton University Hospitals NHS Trust, who led the research, said: "It had exactly the same effect as red wine and could be good for the heart in the long term. In the short term, it might be good for passengers on long-haul flights to take one of these drinks to reduce the risk of deep vein thrombosis."

Mars researchers have also developed a top secret process for replicating flavenols.

The company has patented the discovery and is apparently in "serious discussions" with pharmaceutical companies about the possibility of developing medicines based on the process.

But is the life-prolonging chocolate bar a reality, or a cynical marketing ploy from an industry as greedy as Augustus Gloop, who came to a sticky end in Willy Wonka's factory?

Asked if Mars was seeking to boost sales by attaching a "healthy" label to its products, Dr O'Shaugnessy said: "They didn't sponsor the research.

"We asked them to supply us with the product. "We are constantly on the look out for natural alternatives to preventive medicines for heart disease.

"Clearly Mars will want to promote their confectionery and they are more aware that they have to be conscious of people's health and fitness."

David Haslam, chairman of the UK National Obesity Forum, warned that the claims should be treated with caution. He said: "There are lots of 'good' foods which are also high in calories, like oily fish but if you are overweight you can't tuck into this like there is no tomorrow.

"If they have developed a healthy product that people can enjoy as an occasional indulgence that is welcome but I think the suggestion people should have two a day is overkill. We would need to see good trial data for that."

Masterfoods is not the only company seeking to restore its image. Cadbury Schweppes was severely criticised when it launched its "Get Active" promotion, which encouraged children to buy chocolate bars and exchange them for vouchers for school sports equipment. The campaign was dropped after it emerged a child would have to eat more than 2,000 Dairy Milk bars to claim a cricket set.

Now, Cadbury Schweppes has revived its fortunes with the successful launch of a 99-calorie chocolate bar. The bars are simply slimmer, smaller versions of classic Cadbury products such as Dairy Milk and Bournville.

Announcing the companies half-year results last month, chief executive Todd Stitzer said that the "diet" bars had better profit margins than Cadbury's regular products.

The decision to slim down their products has come at a time when companies such as Cadbury have been under fierce attack for "supersizing", where bigger bars of chocolate are sold at cut-price rates.

The industry has always claimed that extra-large sizes were meant for sharing, but with one million children in the UK now officially classed as obese, the days of supersizing now seem to be over and several firms have announced that they are ditching the policy.

Confectionery companies have also been helped by a slew of research, published in respected medical journals, that highlights the health benefits of cocoa.

Earlier this month, Mars sponsored a conference in Switzerland at which scientists discussed more than 80 peer-reviewed studies on the benefits of flavenols. Among the studies were findings that cocoa flavenols can relax human blood vessels and improve circulation.

Norm Hollenberg, a professor of medicine at Harvard Medical School which helped with some of the research, said: "The mounting evidence on cocoa flavenols is extraordinary.

"This is a scientific breakthrough that could well lead to a medical breakthrough."

Other research has labelled cocoa "Nature's prozac" because it is a good source of mood boosting chemicals such as serotonin and dopamine.

However, nutritionists are keen to point out that the studies are about the cocoa - not the high fat, highly-sugared end product that comes out of chocolate factories. Another gift handed to the industry came recently in the unlikely form of the latest fad diet.

The GI Diet is a regime based on "low glycaemic index" foods that cause a slow, steady rise in blood sugar levels after eating, leaving you feeling fuller for longer. Chocolate is rated as a low GI food, adding to its potential rehabilitation as a healthy option.

Confectionery has also gone ethical.

Cadbury Schweppes bought the organic chocolate company Green & Blacks, while the Co-Op group has pledged to ensure that all its own brand chocolate is made with fairly traded cocoa.

Britain is still the biggest consumer of chocolate in Europe, with an annual intake of 10 kilos of the stuff a year per person.

But while our waistbands continue to expand, sales of chocolate are beginning to slide, with volume sales rising by less than one per cent last year.

The chocolate industry must be hoping that the millions of pounds being poured into the search for healthy products is as profitable as Willy Wonka's golden ticket was for Charlie Bucket.

Mars v CocoVia

Mars advises consumers to eat two CocoVia bars a day to obtain the heart health benefits. Here is the tale of the tape:

Weight: CocoaVia bar x 2 = 46 gms
Mars bar x 1 = 62.5 gms

Calories: CocoaVia bar x 2 = 160 cals
Mars bar x 1 = 280 cals

Fat: CocoaVia bar x 2 = 5 gms
Mars bar x 1 = 10 gms

Carbohydrates (inc sugar): CocoaVia bar x 2 = 30 gms
Mars bar x 1 = 43 gms

A brief history of chocolate

By Kunal Dutta

Approximately AD600 Mayans migrating into northern regions of South America start the earliest cocoa plantations. Using beans from trees, they make a drink called xocoatl.

1505 Christopher Columbus returns from his fourth voyage to America with cocoa beans. King Ferdinand of Spain neglects them in favour of other treasures.

1519 Spanish explorer Hernan Cortes is introduced to the local speciality, chocolatl, by Emperor Moctezuma of Mexico, who gulps several goblets before entering his harem - fuelling beliefs that chocolate is an aphrodisiac.

1528 After the Spanish conquest of Mexico, Cortes returns to Spain with his galleons full of cocoa beans and chocolate-making equipment. It is hidden away in monasteries, keeping chocolate a secret from the rest of Europe for nearly a century.

1579 English and Dutch pirates storm a treasure ship en route to Spain. Mistaking cocoa beans for sheep's droppings, they burn the whole ship in frustration.

1606 Italian traveller Francesco Carletti returns from Central America after observing Indians preparing the drink. Chocolate becomes established in Italy.

1615 The Spanish princess, Maria Theresa, offers chocolate as an engagement gift to her French fiancé, Louis XIII, and Spain's secret is out. France later conquers Cuba and Haiti, setting up its own cocoa plantations.

1657 A visiting Frenchman opens the first chocolate house in London. Each glass costs between 10 and 15 shillings.

1693 John Cadbury prepares drinking chocolate at his grocers in Birmingham.

1849 The Cadbury brothers display edible chocolate at an exhibition in Birmingham.

1866 Holland introduces the Van Houten press that removes the bitter cocoa butter.

1875 Swiss inventor Daniel Peters produces the first chocolate bar using milk. Easter is celebrated with the first chocolate eggs.

1908 Theodore Tobler develops the triangle-shaped Toblerone.

1964 Roald Dahl writes Charlie and the Chocolate Factory.

1971 Gene Wilder stars in the first film version of Willy Wonka and the Chocolate Factory.