Debugger effects Windows Heap?

["RaMatkal" <RaMatkal () hotmail com>]

It was recently suggested to me that a debugged processes heap operates 
differently to when the process is not being debugged (Windows) even when 
you 'attach' with the debugger. (Thus the recomendation to switch off the 
BeingDebugged variable in the PEB when writing exploits).

Firstly, anyone know if this is true?

Secondly, anyone know where i can find any info on this?

Thanks in advance,

RaMatkal