I use Nordic Naturals fish oil, from what I've seen they have the highest quality and highest concentration per tab out there. They are expensive though. I'm not sure about improving anything, I've been taking them for years....2 tabs every morning, afternoon and night and my cholesterol is 120 combined (80 HDL/40 LDL) in fact my doctor told me to lighten up on them as my cholesterol is getting too low. My tryglicerides are running at 50 right now. fish oil helps for sure, my doctor keeps pimping it all the time. That and a supplement called Greens + which I also take religiously.