Grains are bad. Many reasons. But another key thing we've gotten wrong, I believe, are vegetable oils. They didn't exist up until about 100 years ago. The hydrogenated ones like Crisco are really bad. But canola, soy, corn are also very bad for you.
They have high omega 6 content. It is believed humans evolved with around a 1:1 omega 6 to omega 3 diet. Now in America it is mostly 20:1 sometimes way over 30:1. This ratio is incredibly inflammatory and can lead to many chronic diseases.
I believe no one should cook with anything other than coconut oil, ghee, palm, lard, tallow, butter, macadamia oil. You should not use vegetable oils at all in your diet except for good quality first press virgin olive oil, avocado oil, coconut oil, macadamia oil.
You can learn more here: http://www.grassfedgirl.com/12-reaso...ut-the-canola/