New research from Swinburne University of Technology has confirmed what millions of chocolate lovers already knew; dark chocolate improves general calmness and contentedness.

The research found that chocolate is rich in polyphenols, which reduces oxidative stress which is associated with many diseases.

"Anecdotally, chocolate is often linked to mood enhancement," Swinburne PhD candidate and lead author of the study Matthew Pase said. 

"This clinical trial is perhaps the first to scientifically demonstrate the positive effects of cocoa polyphenols on mood."

Seventy-two healthy men and women aged 40-65 years took part in the randomised study to receive a dark chocolate drink mix standardised to contain either 500 mg of cocoa polyphenols, 250 mg of cocoa polyphenols or 0 mg of cocoa polyphenols. The drink mixes were given to participants in identical packaging so that both the investigators and participants were unaware of which treatment they were receiving.