Most of the trans fats in the American diet come from partially hydrogenated vegetable oils. They are created by man to increase shelf life, and they are much worse for us than saturated fats. On the other hand, trans fats produced naturally by bacteria in the rumen of ruminants (like cows) have never been linked to increased disease, and one has now actually been correlated to reduced disease risk (click on image to see reference): trans-palmitoleate in meat and dairy, primarily milk. Since polyunsat