Heart Health

07 January 2009

Should we be eating more chocolate?

Chocolate may indeed be just what the doctor ordered. More and more research is pointing to its positive effects - particularly on the heart. What should you know?

If the very thought of top-quality dark chocolate makes your mouth water, you might want to read further.

Chocolate may indeed be just what the doctor ordered – especially for those at risk of hypertension and heart disease.

But watch out as huge quantities could lead to weight problems, which in itself is a risk factor for heart disease. And chocoholics who prefer to indulge in milk and white chocolate would have to switch to the darker variety to reap the benefits.

The magic ingredient
The key ingredients in cocoa, what scientists call flavanols, are only present in dark chocolate. These flavanols are a sub-class of flavonoids that naturally occur in many plant-based foods and beverages, including cocoa, chocolate, tea, red wine and apples.

Research conducted during the past 17 years indicates that certain dietary flavonoids could have the potential to reduce the risk of heart disease. But in the past, the focus has mostly been on the benefits of tea and red wine.

Now, scientists are saying that the potential benefit of flavonoids could have been underestimated as other potential sources, like cocoa, have only recently been quantified.

A three-way benefit
It looks like cocoa exerts its positive effect mainly in three ways: firstly, by keeping the endothelium (the layer of cells that lines the heart and blood vessels) healthy, thereby reducing the risk of heart attacks; secondly, by lowering blood pressure, which is also related to heart disease; and thirdly, by modulating platelet function in a similar way as aspirin does.

Platelets are the disk-shaped cells responsible for forming clots and repairing small breaks in the walls of blood vessels. When there is too much blood clotting, a heart attack may occur.

A recent, short-term study in people with hypertension revealed a significant decrease in blood pressure after seven days of eating flavanol-rich chocolate every day compared with seven days of eating flavanol-poor chocolate.

Another study revealed that dark chocolate may help lower blood pressure by an average of 10 percent. "We found that three ounces (90g) of dark chocolate per day over several weeks reduced blood pressure in patients with essential hypertension," co-author Jeffrey Blumberg from the Jean Mayer USDA Human Nutrition Research Centre on Ageing at Tufts University told HealthDayNews.

Other studies have compared the effects of flavanol-rich cocoa and chocolate on platelet reactivity to that of 81mg aspirin – and found that the positive effects were more or less similar.

A case in point
But it is the extraordinary example of the Kuna Indians, who live on islands near Panama, which more recently drew the attention of researchers.

These Indians demonstrate very little age-related rise in blood pressure, despite the fact that their diets are fairly rich in salt.

But when Kuna Indians migrate to Panama City, their blood pressure rises with age, reflecting urban levels elsewhere, says Professor Ian Macdonald of the Institute of Clinical Research and School of Biomedical Sciences at the University of Nottingham Medical School in the UK.

The fact that the island-dwelling Kuna love to drink homemade cocoa, loaded with flavanols, is what makes the difference, according to Macdonald.

Kuna who live on the mainland ingest little cocoa, and what they do take in is commercially available and flavanol-poor, while the island dwellers drink about five cups of flavanol-rich cocoa every day and incorporate the cocoa into many recipes.

Here, researchers from Harvard Medical School demonstrated that cocoa not only influences blood pressure control, but that cocoa also has a positive effect on endothelial function.

And what works for the Kuna Indians could very well work for people in other parts of the world, such as South Africa. High blood pressure is a major problem in this country and about six million people are currently affected. Just this year, more than 32 000 South Africans will die of heart attacks.

Controls should be set in place
However, as with other flavanol-containing foods, the type and amount of these compounds present in cocoa and chocolate products are affected by a variety of factors, such as plant genetics, post-harvest handling, processing, and product storage conditions.

For consumers to reap the benefits, control over these processes is essential, experts reckon.

The added bonus is that a potential boom in the cocoa industry will be an economic boost to Africa. In western equatorial Africa, an estimated two million cocoa farmers produce about 70% of the world's cocoa.

So, should we eat more?
It's still early days, and a lot of the research needs to be confirmed before the findings can be put into practice.

"One issue not yet resolved is what the actual daily intake needs to be to confer the benefits, and whether all sources of flavanols have an equivalent effect," Macdonald writes in a study abstract.

In the meantime, it is probably safe to say that a small helping (no more than 10g) of chocolate every day could do no harm – if the chocolate is of the darker variety, and if it forms part of an energy-controlled diet.

– (Carine van Rooyen, Health24, updated May 2008)

- Annals of Nutrition & Metabolism (2005). Abstracts: 18th International Congress of Nutrition. SAJCN, September 2005, Volume 18, Suppl. 1
- Macdonald, I.A. (2005). Cocoa, flavanols and cardiovascular health: what are the public health implications? SAJCN, September 2005, Volume 18, No.2


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