Collagen is a common prorein throughout the body and provides a supporting infrastructure between cells and tissues that basically hold all the components together, muscle, bone, skin,etc. The tunica is composed of more than collagen but they too would benefit from the stimulatory effects of IR as it effects the intercellular matrix, and vascular circulation also.
No, don’t waste money on supplements. Any part of your body will take what it is capable of taking from a well balanced diet. What you don’t take is far,far more important. Like not smoke, strictly limiting additional sugar, controlling blood pressure. Drink lots of water, eat nutritionally dense low calorie natural food. Exercise and get three blowjobs per day. (Ha,ha. Just threw that in there to see if you were still reading).
Good thread. More to come.