I think the latin maxim, "The dose makes the poison" holds true for everything. Everything and and anything can be harmful if taken in the wrong doses for those people. If people are able to be aware and tune into their own bodies, cold showers should be no more harmful than sugar. Autophagy in and of itself is a process of killing damaged cells so it is actually a beneficial process unless it goes on for too long or to too intense a degree. Thanks for taking the time to share a different view of thinking :)