If oysters, mollusks, slugs, or starfish don’t have a brain or central nervous system, it should be ok to eat them.
In the taxonomic rank, these creatures fall under the Kingdom of Animalia, and hence, are animals. As are fishes, snails, monkeys, and even humans.
Although bivalves, like oysters, do not have a central nervous system or a brain, they do have nerve clusters. This allows them to react with their environment in observable and complex ways, like digging, running away, hiding, eating, etc.
Ounce per ounce, oysters have as much cholesterol as beef tenderloin steak.
ALS/Lou Gehrig Disease affects 30k people in USA. The missing link to its cause could be BMAA, a neurotoxin created by cyanobacteria which are found in ecosystems worldwide. Cyanobacteria are approx. 50% of the phytoplankton community of the open ocean covering over half of earth. As marine animals eat phytoplankton, BMAA keeps accumulating in the food chain, from small fish to bigger fish, ultimately inside humans who eat seafood. Although not confirmed nor the only cause, the link is strong. See video for more.

Topic: FAQ – Health