Stephen,
Lots of talk about nutrition and diets in Science Club lately and periodically.
Yes, if a person has specific medical problems there may be very restrictive diets (excluding certain foods), that work for them.
But in general, many people are looking for how to live a long healthy happy life. As a former registered dietitian, what I think is American dietary habits and bastardized foods are basically toxic, unhealthy and killing people. Switching to the eating habits of other countries with healthy populations and longevity is, in general for most people, the place to start making dietary changes.
This article (though not from a scholarly website and with annoying adds) has an excellent list of other countries and the eating habits that Americans in general would be wise to adopt and teach their children:
Lyn Knox