Herring is a type of fish, and you should always be sure to include fish in your diet. Herring is an especially rich source of omega-3 fats, a type of polyunsaturated fat (PUFA) that have anti-inflammatory properties.
Omega-3 vs. Omega-6 Fats
Most Americans today are consuming much higher quantities of omega-6 fats (another type of PUFA that tends to cause inflammation) and this has contributed to many of our current health problems. Our bodies need at least as much omega-3 as omega-6, if not more, to counteract the inflammation created by the omega-6 fats. When we consume too much omega-6 without sufficient omega-3, we open ourselves up to numerous chronic illnesses, including everything from arthritis to diabetes.
Farmed vs. Wild-Caught
The problem with fish is that, due to high demand, many of them come from fish farms where the fish are raised in small pens full of their own filth and pumped with antibiotics. Herring is generally wild-caught though, and Mark Sisson has more suggestions on how to find the healthiest fish.