My experience tells me this is true - the discipline of public health is no more 'evidence-based' than is theology.
Public health, including the research, politics, regulation, and journalism surrounding it, is an inherently dishonest discipline. By that I obviously do not mean that every single person involved is a liar. I obviously do not mean that everything done or written in the area is wrong. What I mean is that the field has no checks on dishonesty. It does not discourage it, and it certainly does not punish it. In most cases, it actively rewards it. There is no culture of duty or honor in the field, and thus no notion of what it means to behave like a real honest scientist. As a result, nonsense abounds. Those who actively take advantage of the opportunity to be dishonest flourish and rise in stature. The resulting core rot permeates the entire space.
Sad I know but true.