All vegetable oils are a healthier alternative to butter and lard because they can be rich in polyunsaturated or monounsaturated fats — both of which can modestly lower cholesterol. But all oils have about 120 calories per tablespoon and can contribute to weight gain.
In addition, studies indicate that normally heart-healthy vegetable oils like safflower and canola may be turned into an unhealthy fat when hydrogen is added to increase their chemical stability (and thereby enhance their potential for use in food products). This process, called “hydrogenation,” transforms these liquid vegetable oils into a more solid and saturated form, known as trans fats.
Advice: Avoid eating trans fats completely. Don’t buy products that say “may contain hydrogenated or partially hydrogenated” oils. Also, deep-fried or processed foods such as french fries, doughnuts, pies and certain cakes usually contain a moderate amount of partially hydrogenated oils.
(Source: Intelihealth website)