How do you tell the difference between natural peanut butter and not so natural peanut butter? In most cases, the oil separates in natural peanut butters and sits on top of the peanut butter.
A natural peanut butter should only have peanuts in it and no added oils or additives. Peanut butter brands like Jif and Skippy have hydrogenated vegetable oils added as an ingredient. Hydrogenated vegetable oil is made through a chemical process that oxygenates the oil and makes it solid at room temperature. One of the purposes for this is to make the food more shelf stable and to keep it from going rancid. And of course, it keeps the oils from separating.
Hydrogenated oil is a trans fat and is not good for your health. Trans fats can cause your good cholesterol to decrease and your bad cholesterol levels to increase. It causes your coronary arteries to become rigid and causes blood clots that can cause heart attacks and stroke. Trans fats can also cause diabetes and cancer.
So in a nut shell, if you care about your health, choose a natural peanut butter with no unnecessary added ingredients.