They are delicious. And now, they also seem to be beneficial for your health. A daily dose of yummy dark chocolate may help patients suffering from the chronic fatigue syndrome (CFS).

According to scientists from Hull York Medical School, dark chocolates have been found to lower levels of serotonin, a brain chemical related to CFS. Serotonin is also believed to play an important role in the regulation of anger, aggression, body temperature, mood, sleep, vomiting and appetite.

The team said patients with CFS found that their symptoms were alleviated when they consumed dark chocolate, much more so than when they consumed milk chocolate that had brown dye added to it. The scientists, however, stressed that the quantity of dark chocolate consumed should be moderate.

Endocrinologist Steve Atkin said, "Although it was a small study, two patients went back to work after being off for six months. Dark chocolate is high in polyphenols, which have been associated with health benefits such as reduction in blood pressure. Also, high polyphenols appear to improve levels of serotonin in the brain, which has been linked with CFS."

According to nutritionist Dr Shikha Sharma, consuming two cubes of dark chocolate is good enough. "Dark chocolates better preserve the benefits of cocoa as they have less sugar in it. Cocoa is rich in antioxidant properties. It's even better when added with resins or nuts. But it has to be consumed in moderation. Consuming bars of dark chocolate can overstimulate the nervous system," Sharma said.

Atkin and his team then carried out a trial on 10 patients to check whether dark chocolate benefited them also. As part of the experiment, the patients received a daily dose - 45g - of dark chocolate or white chocolate dyed to look like dark chocolate for two months.

This was followed by a month in which they were not given any chocolate, before being given the other type of chocolate for two months.

To their surprise, the researchers noted that patients taking dark chocolate reported significantly less fatigue when they started eating the sweet. They also reported more fatigue when they stopped eating it.