They, as it has been put, do not say what you say they said. Your research is not actual research. Don't call 'I did 2 minutes of googling and read one top result' research. It's been addressed multiple times.
ALL and I mean ALL substances can and will fuck you up if abused. Yep - water and air too (do some 'research' on that to find out if I'm BSing you). ALL legit medication is required to test the limits so as to find effective safe doses. So GW, aka Cardarine, was found - in doses at 200x the effective dose -to cause cancer in SOME mice.
Are you gonna take 200x the effective dose? If 20mg a day is the right amount - so 4000mg? No? Then what are the odds of you getting cancer. Practically zero.
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Something else you wanna consider- why the meds were created in the first place. To TREAT MEDICAL CONDITIONS. Not to improve performance or add muscle. Hence how we use them and the doses differs from what will have been studied. It's a good idea to know this cos if a PED, for example, treated high BP and you take it to build muscle then you have the potential to lower your perfectly fine BP to an unhealthy level.