Omega 3 sources often mentioned on this list show up on the USDA data base

http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl

as having no omega 3s.

For example:

Walnuts - zero omega 3s
Macadamias - Zero omega 3s
Leafy green vegetables: asparagus, watercress, lettuce and spinach all
show up as zero
Beef liver - EPA: zero; DHA: 0.2g/100g
Flaxseed - zero
Salmon - EPA: 0.845g/100g; DHA: 0.806/100g.

Can anyone explain this?

We all know that omega 3 content of meats varies widely according to the
food the animals have eaten (e.g., farmed fish fed on fish meal can have
up to 100 times greater omega 3 content than wild fish - analyses at

http://www.evfit.com/fish2.htm

Nevertheless, we could do with some data on the nuts and flax.

Anyone know a reliable and comprehensive source of omega 3 content?
Amadeus - I'd appreciate your advice.

Keith