Partially hydrogenated oil is a type of trans fat that has gotten a lot of flak, and rightfully so. This chemically altered fat is known to raise LDL (bad) cholesterol levels, lower HDL (good) cholesterol levels, and increase your chance of developing coronary heart disease. Many companies are replacing hydrogenated oil with palm oil, saying that's it's a healthier option.
On nutritional labels you might see this ingredient listed as palm-fruit oil, since it's extracted from the fruit of the oil palm tree. This is not to be confused with palm kernel oil, which comes from the palm seed found inside the fruit. Eighty-six percent of the fat in palm kernel oil is saturated (the unhealthy fat), and 50 percent of the fat from palm-fruit oil is saturated, so it's the better choice of the two, but is palm oil considered healthy? To find out read more.
Palm oil is high in saturated fat, and so are butter, whole milk, ground beef, and skin from chicken. These fats should be limited just like trans fats; they clog your arteries and can lead to heart problems. Small amounts of palm oil are seen as safe, but I wouldn't go out of your way to eat foods containing it, and would instead look for foods made with canola or olive oils.
Palm oil has also been in the news over the past couple years for environmental reasons. The palm fruit is found in rain forests, and the production of palm oil is leading to deforestation, which is in turn driving orangutans to near extinction. So if you're concerned about your health and the well-being of the planet, I'm sure you'll be diligently label reading the next time you hit the grocery store.