<human>: Can you provide a brief rundown of the text in within 3 sentences?

My wife and I have a three year old Saint Bernard, who up until the age of two was pretty well socialized with people and dogs. About a year ago he started to become more protective of us and our home and would seem to be slightly agressive towards strangers though we've found that he's actually more frightened and avoids strangers. He's also become a little food aggressive with other dogs but still hangs out with other dogs if we're dogsitting or someone keeps him while we're away. Please note that there was nothing traumatic that caused the change in behavior, we've worked with our vet, a specialist vet at the vet school who works specifically with behavior problems, and two very qualified private trainers. He's also still working with a great trainer and going to be starting a weekly dog camp with this trainer who is very well qualified. 

Now for the big question, would adopting another dog be a mistake or could it help even him out? I ask because we have the opportunity to give a puppy a home because someone we know isn't able to take care of her due to some new developments. What do you think Reddit?
<bot>: we have an anxious/protective three year old Saint Bernard and have the opportunity to adopt a mutt puppy. Would this puppy help his anxiety or could this make things worse?