Trans Fats: the Bad Fat in Town
Related Media: Healthy Eating: Fats and Carbohydrates
Trans fatty acids (trans fats) have gained quite a reputation. Do they deserve their bad rap? The answer is yes. Identifying foods high in trans fats and reducing or even eliminating those foods from your diet is an important way to keep your heart healthy. In fact, it takes such a small amount of these so-called trans fats to negatively impact cardiovascular health that the American Heart Association recommends trans fats make up less than 1% of total calorie intake.
What Are Trans Fats?
The term “trans fat” refers to vegetable oils
(made up of mostly unsaturated fats) that have had hydrogen added to them. This process is known as hydrogenation or partial hydrogenation. Partial hydrogenation of vegetable oils is done to make fats more solid at room temperature, to increase their shelf life by keeping their flavor stable over longer periods of time, and to guard against spoilage. Margarines, shortening, the oils used to cook fast food French fries, and commercial baked goods are all examples of foods that can contain trans fatty acids.
The Harm of Trans Fats
Trans fats not only raise LDL ("bad") cholesterol
levels (as saturated fats also do), they also lower levels of HDL ("good") cholesterol. Trans fat also increases blood triglyceride levels. Several studies have examined the effects of trans fats on cholesterol levels and heart disease risk.
Trans Fats and Cholesterol Levels
A study in the New England Journal of Medicine compared the effects on cholesterol levels of two different diets. One diet derived 20% of calories from fat sources containing varying amounts of trans fats (either soybean oil, semiliquid margarine, soft margarine, shortening, or stick margarine), and the other diet was enriched with butter. The researchers found that the use of soybean oil or semiliquid margarine (which contain the lowest amounts of trans fats) resulted in the most favorable effects on total and LDL cholesterol levels and ratios of total cholesterol to HDL cholesterol. The use of stick margarine (which contains the highest levels of trans fats) had the least favorable effects. The researchers also found that trans fats lowered HDL cholesterol levels to the same degree that saturated fats raised HDL cholesterol levels. So, while both saturated fats and trans fats raise LDL levels to a similar degree, trans fats do the added damage of lowering levels of protective HDL cholesterol. Stick margarine lowered HDL cholesterol levels to a greater degree than sources containing less trans fats.
Trans Fats and Your Health
Eating foods that contain trans fatty acids increases your risk of heart attack
, coronary heart disease
, and stroke. It is also associated with a higher risk of type 2 diabetes.