What's interesting is how much and how little things change. There are certainly things here that would seem strange here (make sure to get two pats of butter every day), but much of advice -- not overeating, watching salt, sugar and fat, satisfying cravings in moderation -- still seems fairly sound.
One of my big concerns with health issues is that the media (and sometimes the researchers) create an exaggerated sense of volatility, the impression that, when it comes to a healthy lifestyle, doctors are constantly changing their mind on everything. Under these circumstances, it's easy to see why so many people fall prey to fad diets or simply give up.
Joseph could give a more nuanced version of this point, but I'm sure that public heath would be better if we stopped presenting a distorted view of health research to the public.