They're a good idea in that increased protein intake is widely considered necessary to gain muscle and whey is widely considered safe. The other side of this

They're a good idea in that increased protein intake is widely considered necessary to gain muscle and whey is widely considered safe. The other side of this coin is that supplements are unregulated so there are various degrees of quality on offer. Also some forms of protein are probably 'safer' than others for most people. For example soy is very bio-active and there are studies showing it having various effects to various degrees (good and bad). So basically stick to whey-products and use something like labdoor quality rankings(https://labdoor.com/rankings/protein/quality https://labdoor.com/rankings/protein/quality) to inform you purchase decisions, use in moderation(i.e one shake after a workout) and you should be fine. My rationale is that I enjoy lifting more than other types of exercise, supplemental protein helps me gain more muscle and get better at it (which I also enjoy), if I didn't do that then I probably wouldn't lift and would suffer the well known risks of not exercising. So known risks vs unknown risks. Basically health research is a shitshow. It turns out a lot of it isn't reproducible. We've been horribly wrong about what is and isn't healthful many times in the past. Be skeptical, do research, and you'll still probably be wrong but at least you tried. (also I'm an engineer/nerd not a M.D and have no formal training in anything- this is merely data being processed by your visual system generating thought)