But flaxseed oil isn't perfect. The better known problem is that it quickly goes rancid. That's why stores usually sell it from refrigerated cases.

The second problem tripped me up. I baked my fish with it. Bad idea. Several websites wised me up.

So, what's the best oil to use in cooking?

After flaxseed oil, the oil with the best omega 6 to omega 3 ratio is perilla oil. Until I read about it in Professor Cordain's book, I had never heard of it.

"Perilla oil (made from the Asian Beefsteak plant) has a healthful omega 6 to omega 3 ratio of 0.27," he writes. "But is rarely found in the United States except for stores specializing in Korean and Chinese foods. Get if if you can."

I can't. My local Asian store is currently out of perilla oil. The only Internet sources that I've found sell it in capsule form.

If I ever find perilla oil, I wonder how much I'll like its taste. "In parts of Asia, perilla oil is used as an edible oil that is valued more for its medicinal benefit than its flavor," Wikipedia says.

Meanwhile, I cook with a great tasting oil that I discovered thanks to Regina Wilshire's "Weight of the Evidence" blog. She has a great post about how much omega-3 and omega-6 fatty acids are in a food or oil.

That brought macadamia nut oil to my attention. While it has little omega 3 or omega 6 oil, its ratio is just fine -- 1 to 1. I now use it on fish when I bake it.