Klaus, flax oil and fish oil are oils rich in Omega 3 fatty acids, also called essential fatty acids because they are essential - and your body cannot produce them, it must rely on what you eat for a supply. There have been a few past discussion on EFA's and fats in general, here are two good links:

http://forum.lowcarber.org/showthre...Oil+AND+benefit

http://forum.lowcarber.org/showthre...highlight=Omega

HTH,
Nat