I just realized I owe a piece on krill oil that I promised from a previous post about fish oil. Here's the deal. Krill are tiny shrimp-like crustacean creatures that whales feed off of. Krill oil contains a lower amount of the omega-3 compounds EPA and DHA than fish oil, however, it has several advantages.
Omega-3 in krill oil is attached to a phospholipid while the omega-3 in fish oil is attached to a triglyceride. Since our cell walls are constructed of phospholipids the omega-3 in krill oil is more easily absorbed and put to use. Meanwhile, the triglyceride in fish oil has to be broken down before the omega-3 becomes available. This happens in the gut, and so a large portion of the omega-3 is eliminated in the intestine.
Another advantage that krill oil has is that it is naturally high in a potent antioxidant called astaxanthin. This makes the oil much more resistant to oxidation and going rancid, a problem inherent with fish oil. Plus, you get the benefit of this powerful antioxidant to fight your own free radicals. Finally, krill are at the bottom of the food chain, so they are much lower in environmental toxins than fish.