30 years ago i started with Knox Gelatin in my heavy training times. For many years i have been using chicken and beef to get types 1,2 and 3. Have some marine collagen on the shelf to add types 4 and 5 into the blend. I think it can help to slow down the degeneration of joints and tissues. Studies show that most all the collagen gets broken down into animo acids from what i read. Collagen is a pretty big molecule and is hard to absorb. When i hear people talk about starting is and within a couple days they noticed results i see placebo effect flashing.
Been taking Hydrolyzed Beef Collagen (currently from True Nutrition) and UC-II Collagen (currently from Swanson) for around a decade. Joints feel good and haven’t torn anything. Doesn’t mean collagen is the reason why, I could’ve been this way without those but I like to think it’s helped.