Facilitative and functional fats in diets of cats and dogs.

I n human health and nutrition, the concept of good fats and bad fats is typically used, especially with respect to dietary risk factors for coronary artery diseases and stroke. This concept originated with the notion that there are 2 forms of cholesterol that, for the sake of simplicity, have been referred to as good and bad. The concept has now been extended to include other dietary fats that may also be associated with increases in cholesterol concentrations. Dietary fats, including cholesterol, are transported in the blood as lipoprotein complexes. They include LDLs and HDLs. 1 Because LDL, which transports cholesterol into tissues, is involved in the formation of ath-erosclerotic plaques in humans, it is considered by health professionals to be the bad form of cholesterol. This is especially the case when there is an overabundance of cholesterol that can become deposited in arteries, which results in atheromatous lesions. By contrast , HDL has the capacity to transport cholesterol away from tissues and is thus considered to be the good form of cholesterol. The amount of cholesterol each of the lipoproteins carries, relative to the total amount of cholesterol, partially determines the amount of risk that an individual may have for developing ath-erosclerosis, coronary artery disease, or stroke. Thus, for humans, fats containing LDL cholesterol are bad fats and fats containing HDL cholesterol are good fats. Other than cholesterol per se, dietary fats containing specific fatty acid types are also considered to be bad or good for humans, depending on whether they have been associated with increases or decreases in total plasma cholesterol concentrations. 2 Fats that predominantly contain saturated fatty acids are referred to as saturated fats, whereas those containing high proportions of polyunsaturated fatty acids are termed polyun-saturated fats. Saturated fats from animal and some plant sources that typically increase cholesterol concentrations are examples of bad fats. By contrast, good fats generally include polyunsaturated fats, containing omega-6 fats from oilseeds that typically lower plasma cholesterol concentrations. Polyunsaturated omega-3 fats from marine sources typically decrease inflammatory processes and blood pressure 2,3 and also result in several other desirable effects; they are also considered good fats. In general then, polyunsaturated fats are considered to be good fats. 2 Even CLA, a type of polyunsatu-rated fatty acid, is considered by some to be a good fat, and researchers continue to investigate its effects. It has been proposed 4,5 that CLA may …