The press release had a curious title: “Omega-3 fatty acids protect against Parkinson’s.” The certainty suggested an experiment, but Parkinson’s is too rare to study prevention experimentally. The press release turned out to be about a rat study that used a drug called MDPT to cause brain damage that resembles Parkinson’s. Rats given a high-omega-3 diet suffered much less damage — apparently none — from the drug.
Rats given the high omega-3 diet had much less omega-6 in their brains than control rats — one more reason, in addition to the Israeli Paradox, to think that omega-6 may be just as bad as omega-3 is good. Omega-3 may act by displacing omega-6 (they are almost identical physically).
The results could have been taken to suggest both (a) eat more omega-3-rich foods, such as fish and (b) eat less omega-6-rich foods, such as vegetable oils, but only the first recommendation reached the public.