Soy is high in anti-nutrients, such as lectins and phytic acid, and polyunsaturated fats (PUFA), particularly omega-6 fats, which are inflammatory. Squeezing out the fat you can get from soy beans into an oil doesn’t make it any more appetizing. It’s just a concentrated source of omega-6 fats, often derived from GMO beans and hydrogenated beyond recognition.
The Fat Profile
Soybean oil is mostly PUFAs and almost all of those PUFAs are omega-6 fats (which are inflammatory), followed by monounsaturated fats, saturated fats, and just a small percentage of the beneficial omega-3 fats.
Paleo and PUFAs
PUFAs are unstable when exposed to heat and light and hydrogenating them doesn’t do anything to help matters (in fact, it often makes them worse). The result is a bottle full of oxidized fat that, when consumed, is likely to cause the development of oxidized cholesterol in the blood stream.
Mark Sisson included soybean oil in his list of edible oils to include or avoid as part of a healthy lifestyle.