defo - salt and saturated fat and whatever hormones + antibiotics were injected into the pig before slaughter ...
Regarding hormones, I refer you to EC Legislation. Council Directive 96/22/EC (OJ L125, p3, that states... prohibit the use of substances having a hormonal action for growth promotion in food ...
Hormones in meat is one of those myths that just won't die.
Regarding antibiotics, there is also an EU directive that includes a mandatory withdrawal period to ensure no antibiotics are in the animal when slaughtered.
If you're still concerned, you can get really good organic bacon in most supermarkets now.