Guild Wars 2

According the the Wiki ;
http://wiki.guildwars2.com/wiki/Food#Healing_Power

Foods like Mashed Potato’s provide a Negative to Stun damage or is the Wiki just buggered?

It means that you are stunned for less time, not that your stuns are less effective.

stun doesn’t do any damage

this consumable buff lowers the duration of stuns applied to you.