Dad with Alzheimer's started taking Flax seed tablets. Does it have any real side effects?

I haven't heard anything bad about it. I have wondered if it has all the good effects that it is supposed to. Some people use it for their pets when they have chronic illnesses. It is supposed to be very good for the digestive and respiratory systems, but I don't have any firsthand knowledge. Has it had any positive effects that you've noticed with your father? I would love to know if all the claims are true. If they are, then we all should be taking flax seed!