Just when you thought you understood trans fats (and to understand them is to avoid them like the plague, right?), new information surfaces showing that not all of these fats are bad. (Search: Good fats vs bad fats)
A recent review published in Advances in Nutrition suggests we reboot our thinking and labeling processes for trans fats, based on the fact that there are two different types of trans fats—synthetic, or industrial, trans fats and natural, or ruminant, trans fats—and the latter variety has shown to be harmless or potentially beneficial.
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What’s the Difference?
The more ubiquitous and talked-about family of trans fats is referred to as industrial or synthetic trans fats. These are man-made and also known as partially hydrogenated oil. These are manufactured by bubbling hydrogen through fat at a high temperature in the absence of oxygen, thus preventing the fats from going rancid when they absorb oxygen and decomposing, which is what happens with unsaturated fats found in avocados and olive oil. The process also changes the molecular structure of the fat, turning the oil into a semisolid substance with about the same consistency as butter or shortening. Synthetic trans fats were initially introduced to minimize the amount of saturated fats we used. They also contain properties that preserve foods, prolong shelf life, and help with texture, so you’ll find them most often in cookies, cakes, shortenings, crackers, and dry food.
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It’s this family of trans fats that has been linked to increasing the risk of a number of chronic diseases, according to Spencer Proctor, one of the review authors and director of the Metabolic and Cardiovascular Diseases Laboratory at the University of Alberta in Canada. Synthetic trans fats have been shown to raise our bad cholesterol, lower our “good” cholesterol, increase inflammation, and possibly increase triglycerides. “All of these affect our heart and increase the risk of heart disease,” says Vandana Sheth, RD, CDE, spokesperson for the American Dietetic Association. They are also known to trigger inflammation and overactivity of the immune system, which may contribute to stroke, diabetes, and other chronic conditions in addition to cardiovascular issues.
Scientists are still unclear as to why trans fats raise our LDL levels, but one theory is that the addition of hydrogen to oil during the hydrogenation process might make it difficult for us to digest.
According to the USDA’s dietary guidelines, we should limit our synthetic trans fat consumption as much as possible. The American Heart Association has a more specific guideline. It suggests that trans fats should make up less than 1% of your total calories. So for a 2,000-calorie diet, you should consume no more than 2 g of trans fats daily.
The health risks were portrayed as so dire that a number of measures regulating its use have been taken. Cities, including Philadelphia and New York, banned its use in restaurants. California issued a partial statewide trans fat ban, and Kraft Foods reduced or eliminated trans fats in 650 products. “[Synthetic trans fat] is the family we’ve tried to remove from the food chain, and we’re doing quite a good job,” Proctor says.