doing a deeper dive on Chitin - I don't think any of the scientific studies on it are that conclusive

Chitin is abundant in a lot of seafood too and cultures that consume a lot of it (Japan) have some of the healthiest and longest living populations 

 Chitin is largely indigestible. Mushrooms contain a lot of it, it's where extraction (boiling, ethanolic) helps break it down to make it more bioavailable.