He means hungry/thirst afects your regen.
Think, if you played a fire giant it would be worse.
Managain helps increase your %of mana regen per tick.
Sleeping just before a tick is an art form for mages/clerics.
Spells for example afect your hit mana regen.
A classic one is Paladins Heroism. A full speled Elf Pal only get about 100 mana regen.
Of course those communers that devote themself to the search of greater Knolage will find ways to inprove their mind regeneration. 
Now an advice, forget 103% meditation and get +managain eq.