On the day of your exam, it is recommended to have 150 gms of Dark Chocolate.
There are no scientific evidences to prove your performance after eating a chocolate. However, for ages now our candidates have been able to face the exam with more confidence, sustain the temperature in the exam hall, withstand hunger till the exam gets over, controlled blood pressure and boosted flow of oxygen altogether help candidates do well with their exams.
Dark chocolate is a rich source of antioxidants and minerals, and it generally contains less sugar than milk chocolate. Some research suggests that dark chocolate may help lower the risk of heart disease, reduce inflammation and insulin resistance, and improve brain function.
People who are interested in adding dark chocolate to their diet should keep in mind that it is high in fat and calories, so moderation is key.
Try having a dark chocolate on a typically busy day. See how it influences on you. If you fell good you can have it on the day of the exam.
Disclaimer: Nothing is official about it.
There are many websites and blogs that mention about the benefits of having Dark Chocolates. Read it to know more about it.