High oleic oil is any oil that is high in monounsaturated fats. Olive and canola oil are naturally high in monounsaturated fat, but they are also high in polyunsaturated fats which mean they are not very shelf-stable.
In the past, food companies used hydrogenated oils (trans fats) to keep food shelf-stable and preserve flavor. When companies had to stop using trans fats, they switched to high oleic oils or palm kernel oil to make their food last longer for customers. These oils are often used in packaged baked goods (packaged cakes, cookies, etc), as spray coating for cereal, crackers and dried fruit; and in non-dairy creamers as well as many types of frying.
High oleic oil is high in unsaturated fat, low in saturated fat, and has no trans fat. The large amount of monounsaturated fat in high oleic oil has been shown to lower LDL cholesterol (the bad kind) without lowering HDL cholesterol (the good kind). When LDL cholesterol goes down, so do the risks of heart disease, heart attacks, and stroke.
It’s pressed from sunflowers that have been bred to be high in monounsaturated fat (MUFA), which is the primary type of fat found in olives and avocados.
As WebMD states, high oleic sunflower oil mildly increases blood sugar and influence insulin level. Therefore, people with type 2 diabetes can experience the side effect of developing hardening of the arteries. Several studies prove that allergic reactions to sunflower oil are very rare cases. Their main symptoms can be swelling, skin rashes and itching, stomach cramping, nausea and vomiting. Highly refined oil usually does not provoke allergy.
Another high oleic sunflower oil side effect is documented, according to the article in Journal of the National Cancer Institute (2001). High levels in the body of both oleic and momounsaturated fatty acid are associated with the increased risk of breast cancer.
High oleic sunflower oil, like any other oil indeed, is 100% fat. Only one tablespoon of the oil contains 120 calories. Therefore, eating a large quantity of high oleic sunflower in a day will use up a great percentage of daily caloric allowance and can lead to weight gain.
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Source: EatingMadeEasy, http://eating-made-easy.com/what-is-high-oleic-oil/