A year or two ago, I noticed that my ears (mostly the left) would get sore during the night. I assume it was pressure on the cartilage. Some time after I discovered my sensitivity to proline, and reduced my intake of it, I noticed that I no longer developed sore ears. That's hardly a solid cause and effect, but it does seem like the most likely reason for the change, since proline is so important for cartilage development/maintenance. So, for anyone who suffers from cartilage pain and is desperate for relief, experimenting with a low-proline diet might be worth trying. However, some people might have cartilage problems that are made worse by reducing proline, so watch for that.