The word "natural" doesn't mean "part of nature" when speaking of nutrition, it means "part of our evolutionary history." We ate lard in the past(and survived because of it, and evolved toward making use of it.) We did not eat cyanide.
Semantics aside, I'll gladly grant you that lard is a food that has been eaten in the past. But, once again, that doesn't mean it's necessarily better than other foods that haven't been eaten in the past.
An good example is "golden" rice. An argument could be made (and has been made) that golden rice could save millions of people from devastating vitamin deficiency which they would continue suffer from were they to avoid golden rice for their "traditional" foods.
Plenty of traditional foods just aren't very nutritious or healthy.
I think that tradition, like cuisines, is an ever changing thing, however.