Fresh fish harbors the healthy kind of fat.

One of the most exciting nutritional facts about fish regards omega-3 fatty acids. Fatty fish from cold-water regions, such as tuna, salmon, mackerel, and sardines, contain this kind of fat. These healthful fats reduce the risk of heart disease.

Yes, fats can do that. The three major categories of dietary fats -- saturated, monounsaturated, and polyunsaturated -- have effects on less desirable LDL cholesterol and on the more desirable high-density-lipoprotein (HDL) cholestorol levels. Saturated fats, in general, have been shown to elevate LDL cholesterol levels, and high levels of LDL cholesterol are a major risk factor for heart disease.

In contrast, diets high in monounsaturated and polyunsaturated fats lower LDL cholesterol levels. The polunsaturated fat category contains two subclasses of fatty acids: omega-6 (n-6) fatty acids and omega-3 (n-e) fatty acids.