What dreadful person would feed a dog anything but meat? Nevertheless, a mastiff will eat darn near anything. Broccoli gives them (gag) very bad gas. I have no idea what tofu would do, as there has never been any in my house.
But he will likely not an “acorn.” Might play with it, mess it up some...;-D
Our dog loves carrots. I can see number of ways in which these are good for him and since a vet concurs, I don't think we are dreadful people.