Dark chocolate has been "proven" to increase the performance of (amateur) athletes competing in endurance sports.
What all these articles have in common is:
They are all based on the same study, from Kingston University. The study went on for only four weeks, and there were only 9 cyclists that were part of the study.
I don't doubt that the scientist at Kingston made these observations, and that the athletes did in fact perform better. However, there are many outside factors that could influence these results, and the margins of errors seems to be very high.
Has this study ever been confirmed by any other scientists? I can't find any references verifying the study, only loads of articles saying "Eat dark chocolate!"