I have no scientific source but I saw a Swedish TV program about food and there they said that the American diet are expected to have the taste of salt, sugar and processed fat. And that we as humans often select food from our expectations on how it is supposed to taste. And that we learn that when we are young.

It was about on how important the food in schools are for the general health and how it affected the eating behaviour when you grow up.

If I remember correct the tv program where called History eaters but in Swedish of course Historieätarna.