What is the fundamental difference between nutrition and something like evolutionary biology? With evolution, there are obviously a lot of people who don't believe it, but pretty much everyone (including the doubters) recognizes that the mainstream scientific consensus is that evolution is a correct theory.

So, is the difference that there isn't much consensus among scientists for nutrition, and if so, why not? It seems to me that a hypothesis like "salt consumption affects blood pressure" should be fairly straightforward to test.

Or is the difference that the public simply isn't aware of what the scientific consensus is regarding issues in nutrition?