I've seen the question come up on Dr. D'Adamo's board, but don't remember the explanation. In general, when a food in different forms has different values (pineapple versus pineapple juice; peanuts versus peanut oil) it is because whatever is good (or bad) is more (or less) concentrated. The one thing I did find in searching Dr. D's board is that fish oil can cause mood disturbances in type O.

Personally, that sounds like that kind of thing one could test individually.