Never heard of Dr.Yu but then I found doctor Hoffer on the internet and saw he has written a lot of books. As far as niacin most of my information was just from FAQ here on the Iodine forum.
The problem of the video's is there are not enough answers.
Personaly I have never liked sauna's too much but I do like steambaths. So the question is would a hot bath help or steambath instead of a sauna.
About the baths that was also asked by other people reacting to the video.
My interest in niacin is mainly for cholesterol, it helped before and I have started up again.