Pork Leg Bone Soup

I found "pork leg bone soup" is extremely health! Lots of calcium and other nutrition factors. And it's so easy to digest.
I was feeling quite fatigue several days ago but this soup changed my energy level almost immediately. This was also because I felt I wanted this soup! My body was telling me what it wanted (and this made things so easy!).
This soup as matter of fact is popular among Chinese people (that's why I can only get it from Chinese supermarket), but somehow I did not make it often before. Now I acknowledged its "power" and will make sure to include it in my regular diet.
I learned several "tricks" to cook this soup:
1. cook it for hours until it turns white;
2. after water was boiled put some sliced ginger roots and little vinegar (vinegar can make calcium dissolved quite thoroughly into soup).

3. right before the water was boiling, clean those floating stained stuffs carefully to make the soup clean.