Same for iron. Spinach has a lot of iron, but your body does not absorb it. That's where heme iron comes into play.

Heme iron comes from meat, fish, and fowl (of course, fish and fowl are also meat).

Plants are extremely hard to digest. That's why cows have multiple stomachs, they ferment their food and chew it again and again. Horses have extraordinarily long intestines to keep it in the digestive juices longer, and other animals eat their stools and find nutrition in them. Rabbits, deer, and others eat their own stools to pass them through the digestive system again.

Back on topic, I don't think we humans evolved to eat and digest vegetable oils. Of course, that doesn't in itself mean they are bad for us, but other studies have show just how inflammatory they are.

But the food industry is more concerned about their profits than they are about your health. And since the agencies that are supposed to regulate the food industry are filled with food industry shills, that isn't going to help. So we have to watch out for ourselves.