This is also the "secret recipe" from the book, "Why French Women don't get fat". I remember seeing the author on Oprah and she said she'd do this for a day or two every once in a while to detox...
EC: Aginto is referring the recipe at the top of the Leek Soup page.
Just want to clarify, drink only the leek soup without eating anything the whole day when having a flu? Chicken soup is what we're having when a family member has colds or flu but we also eat 3 regular meals a day so we will not get weak.