Bro, I've put on 40ish pounds in the last 12 months taking a shitload of protein (upped it even more than it was before) and some creatine (10g on training days, 3-5 on off days). I've also done 3 cycles of M1T, so I guess you could say that I'm not 100% natural, but I firmly believe that I would've still gained at least 20-30lbs without it.
You can get a very nice physique naturally, but like's been said before on here, juice is just a quicker way to do it or only truly necessary if you want to be a freak.