You should have BOTH, but since most Americans easily get enough saturated fat (most of it comes from animal sources - meat, cheese, milk, butter), health advocates usually downplay saturated fat and highly promote unsaturated fat (mostly from plant sources such as olive oil, nuts, seeds). Unsaturated fat helps keep cholesterol levels in check. Saturated fat is a source of cholesterol. But don't let them brainwash you into thinking saturated fat is bad like trans fats. You NEED cholesterol from saturated fat to build new cells, produce hormones, and have a healthy brain, etc. Pregnant and nursing mothers especially need saturated fat for proper development of their baby's brain. For this reason, vegan moms should strongly consider going vegetarian during pregnancy and nursing.