I'm something of a minimalist when it comes to supplementation. I use Whey protein, and sometimes Casein in the evening. I like Creatine Mono, and I use it year-round. Multi-vitamin and fish oil, and that's about it.
It is common knowledge that a 17a PH can put a strain the liver so many advise using natural supp's to provide protection and strickly advise no booze.
As with any serious supp there is the potential for issues and so there are many different supp's to help minimize problems but these can be better suited to the specific supp being run. There are the "all in one" protector's available.
There are two sides to this where some will say they ran a cycle without anything and the flip side where people pre load supp's weeks before and all through and then after their cycle.
Personally, my vote would be for anything to control BP.
(some examples - hawthorne berry extract, celery seed)