The viscera are not edible: the viscera of oysters can easily harbor heavy metals and other seaweed or pollutants, which can cause discomfort even after cooking. Therefore, it is recommended to eat only the white meat part of the black viscera part of the elimination is appropriate.
Oyster shells can not be eaten directly: the oyster shell is mainly to play a protective role, so the oyster shell is very hard, the oyster shell will be covered with algae and microorganisms, etc., after eating may cause discomfort, so it is generally not recommended to eat oyster shells directly.