Updated on 3/30/2005
You've asked a good question about a rather confusing subject. The African oil palm (Elaeis guineensis) or its American hybrid variety (Elaeis oleifra) is widely cultivated in tropical areas and produces a fleshy fruit from which two oils are extracted: (1) palm oil from the fruit and (2) palm kernel oil from the pit. Both contain a lot of saturated fat, but of the two, palm oil is the healthier, both because it has less saturated fat and because it has high antioxidant activity from a significant content of natural vitamin E (including both tocopherols and tocotrienols). It can also be extracted gently by pressing the pulpy fruit.
Rees Moerman, product engineer at Spectrum Naturals, a California company, which sells high quality expeller-pressed oils, tells me that unlike palm oil, palm kernel oil can't be obtained organically. Instead, the oil must be extracted from the pit with a gasoline-like hydrocarbon solvent. In short, palm kernel oil is a cheap, unhealthy fat, and I recommend avoiding food products containing it.
Fractionation is a further phase of palm oil processing, designed to extract and concentrate specific fatty acid fractions. Fractionated palm oil, as found in food products, has a higher concentration of saturated fat than regular palm oil and is used for the convenience of manufacturers who like its stability and melting characteristics. The healthful aspects of natural palm oil are largely lost in the process. I've noticed that fractionated palm oil is a common ingredient in many power bars sold in health-food stores.
The bottom line is that of all these oils, organic, minimally processed palm oil is the healthiest, followed by conventionally processed palm oil. Palm kernel oil is less healthy still, and fractionated palm oil is the least desirable.
Andrew Weil, M.D.