Yes, you can put collagen in hot coffee. Heat unfolds whole collagen, but hydrolyzed peptides are already unfolded and cut, and coffee is far too mild to break them.
Yes, modestly. Trials of hydrolyzed collagen in active adults found less joint pain during activity after 12 to 24 weeks. Here is what the research shows and what it does not.
Collagen studies used 2.5 to 15 grams a day. See the dose tested for skin, nails, joints and training, how long results took, and what it means in scoops.