How come claims regarding nutritional value keep changing?

I just came across this Web site and my initial reaction was that they must be kidding. Fat, including saturated fat, is good for you? It is like a scene out the Woody Allen movie Sleeper. How can we take so called nutritional scientists seriously? Are there experiments properly set up? Do they use sufficient controls and large enough sample sizes?

Here is what I think should be done. Create a huge nutritional study sponsored by all the world’s industrialized nations. Include 1000 or 10,000 or whatever size sample is needed to draw proper conclusions. Hire the subjects and pay them full time salaries to have their diets monitored and possibly controled. Do tests for anything that could influence health – carbohydrates, fats, proteins, alcohol, caffeine and whatever else anyone can think of. Have everyone monitored for everything and use correlations to find the impact of relevant factors. It will be expensive, but it will be a one-time conclusive study that would more than pay for itself with the benefits that the conclusions could provide.