a flavour of its content
As for the evidence and bias, I think a big part of the problem is the way marketing departments from food corporations glom on to any tiny shred of evidence to sell their wares, no matter how ill-supported or tenuous.
The push to give bananas a reputation for potassium, to give milk a reputation for calcium, blueberries for antioxidants, etc. are all examples of this phenomenon.
These minor claims of potassium or calcium or whatever other content in the food may later be refuted, but until that actually happens these claims serve as great tag lines to make people think the products are healthy and should be ingested more frequently... hence driving up revenue.
Regarding the food labels and claims, I heard an interesting story this evening on NPR. They asked people who have worked in the label industry for years what types of information THEY'D like to see on labels, and they cited things like, "What was your source of water for this food, and how much did you use? How much fertilizer did you use for this food, and how did you control for runoff? Did you pay your workers a living wage, and how many received benefits?" The idea is that while labels are helpful, there are countless other things about which we should be informed when choosing food purchases.