Partially vs. Fully Hydrogenated Oils

The Truth About Trans Fats

Peanut butter contains a tiny amount of partially hydrogenated oil
Tom Grill/The Image Bank/Getty Images

While scientists dispute the benefits and hazards of saturated fats, they are in full agreement that partially hydrogenated oils (or trans fats) are harmful. This inflammatory food ingredient raises your bad cholesterol (LDL) while lowering your good cholesterol (HDL), making it a contributor to heart disease, according to some studies. In fact, the U.S. Food and Drug Administration now requires all food companies to phase out artificial trans fats (or partially hydrogenated oils). However, they still exist on the shelf—and may sit there for years, too—as distribution needs to cycle itself through. If you happen to pick up one of these "phased out" products that claims "trans-fat-free," you may still see partially hydrogenated oils listed in the ingredient list. It's a marketing gimmick with a workaround and one you'll fully understand once you uncover the facts about this nuisance additive.

But first ...

What Is Hydrogenation?

Hydrogenation is the chemical process by which liquid vegetable oil is turned into a semi-solid fat in an effort to cost-effectively change its physical properties for food production. But, breaking down a food's natural properties makes it unrecognizable by the body, ultimately causing harm. Such is the case with partially hydrogenated oils which contain trans fatty acids. These trans fats not only tweak cholesterol levels in the body, but they are also linked to a myriad of diseases, including stroke and diabetes.

On the other hand, fully hydrogenated fats—processed in the same chemical way—contain virtually no trans fats. The resulting product is firmer than its partially-hydrogenated counterpart and has a hard, waxy consistency, even at room temperature. Fully hydrogenated products do contain saturated fat in the form of stearic acid, a monounsaturated fat that doesn't raise levels of bad cholesterol. This makes fully hydrogenated fats less harmful than partially hydrogenated fats. But are they good for you? Not exactly—only slightly better.

What's on the Label?

There are two reasons why foods containing hydrogenated oils are labeled "trans-fat free" or said to contain 0 grams of trans fats. First off, products that list partially hydrogenated oils in the ingredients, but contain less than 0.5 grams of trans fats per serving, are considered—by the government—trans-fat free. Look at non-organic brands of commercial peanut butter, for instance. Most contain a small amount of partially hydrogenated oil to prevent separation on the shelf. But even still, this product manages to fly under the trans-fat radar. However, if you eat more than the suggested serving size, those fractions of a gram add up, and suddenly the amount of consumed trans fats becomes measurable. The second contributing factor to questionable labeling is that products with fully hydrogenated oils are, truly, trans-fat free, adding to the misconception that what you are purchasing is a healthy alternative, when it really isn't.

Ambiguity of Terms

Lastly, beware of any package that simply lists "hydrogenated oil" in the ingredients, without specifically stating whether it is partially or fully hydrogenated. Sometimes the terms "hydrogenated" and "partially hydrogenated" are used interchangeably and incorrectly, leading to the purchase of a food item you think is trans-fat free, but really isn't. Only if the package clearly states that the food contains "fully hydrogenated oil" are you're good to go. But trans-fat free or not, the healthiest option is to steer entirely clear of food containing processed oils.