I've seen lots of studies about Types 1 and 3.
I've seen lots of studies about UC-II, undenatured collagen type II.
I am specifically referencing collagen type II (the one dosed in 2.5g on average, not UC-II which is dosed at 40mg on average).
I reference pills because collagen type 2 powder usually doesn't exist. Although some companies mix it in wither other kinds, it's usually pills. For example Neocell makes pills.
Do you know of any studies that show that collagen type 2 does something useful or harmful?