Basics Why Hydrogenation Is Bad for Fat By Shereen Lehman, MS Shereen Lehman, MS, is a healthcare journalist and fact checker. She has co-authored two books for the popular Dummies Series (as Shereen Jegtvig). Learn about our editorial process Shereen Lehman, MS Fact checked by Fact checked by Andrea Rice on October 12, 2020 facebook twitter linkedin Andrea Rice is an award-winning journalist and a freelance writer, editor, and fact checker specializing in health and wellness. Learn about our editorial process Andrea Rice Updated on October 12, 2020 Print littleny / Getty Images You've probably been hearing the hype about hydrogenated fats. What does it mean if a fat is fully hydrogenated or partially hydrogenated? Is this the same thing as saturated and polyunsaturated fats? Where do trans fats fit in? What do you need to know about fat, both the good and the bad, in order to make wise dietary choices for yourself and your family? Understanding Fat Hydrogenation Hydrogenation is the process by which hydrogen is forced into heated vegetable oil by using a catalyst such as nickel. Forcing hydrogen into the oil changes the chemical structure from a liquid into a more solid shape. Oil can be partially hydrogenated or fully hydrogenated. Both partially and fully hydrogenated fats are considered saturated fats. You may ask why would a food manufacturer want to alter fat in this way. This will become clearer as we define these terms below, but one of the primary reasons is to alter the consistency of the product. Another reason is to increase shelf life. What Is Partial Hydrogenation? Partially hydrogenated oils contain trans fats that give them a soft, buttery consistency. Food manufacturers may use partially hydrogenated oil in processed foods, baked goods, and stick margarine because it lasts longer than regular oil and gives pastries their texture. Partially hydrogenated oils have fallen out of favor due to the trans fats that are created by the hydrogenation process. The sad part is that partially hydrogenated vegetable oils were originally thought to be a healthier alternative to saturated fats, some of which are associated with cardiovascular disease risk. But it turns out that trans fats are even worse than saturated fats. The trans fats found in partially hydrogenated fats raise your LDL cholesterol levels (the bad kind) and lower your HDL cholesterol levels (the good kind) at the same time. So eating trans fats raises your risk of developing heart disease and stroke. It’s also linked to developing type 2 diabetes. Heating and reusing partially hydrogenated fats may also be a problem, with a 2016 study suggesting that the amount of trans fats increases when partially hydrogenated fats are heated to 180 to 220 degrees F. It did not matter what method of cooking—heating, reheating, frying, or refrying—was used. Trans fats are considered bad enough that they are required to be listed on Nutrition Facts labels, and their use has been banned in some places (artificial trans fats are banned throughout the the United States). If you live in a region where foods aren't required to be labeled with trans fats, look for the words "hydrogenated" or "partially hydrogenated" on the label. Decoding the Health Claims on Food Labels What Is Full Hydrogenation? Fully hydrogenating oils makes them solid, similar to the saturated fats found in meat. Fully hydrogenated oils are probably better for you than partially hydrogenated oils, but we wouldn't say they're good for your health—maybe less dangerous is a better way to put it—because they don't contain the trans fats. Fully hydrogenated oils are mostly stearic acid, which is a less harmful form of saturated fat. Stearic acid have a neutral affect on LDL cholesterol levels, and it's relatively stable, so it's good for kitchen use. The problem is that fully hydrogenated oils are solid and waxy, so they're difficult to use. They can be blended with polyunsaturated oils like soy and sunflower oils through a process called interesterification to improve the texture and soften it up a bit. The problem is that research isn't clear on how these interesterified fats will impact cholesterol levels and cardiovascular disease risk. Calories Both partially and fully hydrogenated fats are high in calories. All fat has nine calories per gram. Saturated vs. Unsaturated Fats If you are reading food labels it can be confusing. For example, partially hydrogenated fats and polyunsaturated oils can be easily mixed up. Polyunsaturated fats, in contrast to partially hydrogenated fats which are a form of "saturated fats," can actually be good for you (within limits). Learn more about the differences between saturated and unsaturated fats. Bottom Line So, are hydrogenated fats bad for you? Partially hydrogenated fats are concerning because of the creation of trans fats, and trans fats are unhealthy in a balanced diet. If you find either partially or fully hydrogenated fats in products in the grocery store, it's also likely that they will be found in heavily processed foods—foods that are usually unhealthy anyway. To make this more practical, check out some of the foods containing saturated fats that are best avoided. Many nutrition specialists now recommend shopping in the periphery of the grocery store. Foods that do not have labels, such as fruits and vegetables, plus foods that are not highly processed, such as fresh meats and dairy products, are usually found in the outer areas of the store. To make this more fun, try grocery shopping without walking through the aisles, with the exception of picking up some monounsaturated or polyunsaturated oils such as olive oil or canola oil. Was this page helpful? Thanks for your feedback! Looking to lose weight? Our nutrition guide can help you get on the right track. Sign up and get it free! Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Iqbal MP. Trans fatty acids - A risk factor for cardiovascular disease. Pak J Med Sci. 2014;30(1):194-197. doi:10.12669/pjms.301.4525 American Heart Association. Trans Fats. Updated March 23, 2017. Islam MA, Amin MN, Siddiqui SA, Hossain MP, Sultana F, Kabir MR. Trans fatty acids and lipid profile: A serious risk factor to cardiovascular disease, cancer and diabetes. Diabetes Metab Syndr. 2019;13(2):1643-1647. doi:10.1016/j.dsx.2019.03.033 Bhardwaj S, Passi S, Misra A, et al. Effect of Heating/Reheating of Fats/Oils, as Used by Asian Indians, on Trans Fatty Acid Formation. Food Chem. 2016;212:663-670. doi:10.1016/j.foodchem.2016.06.021 Astrup A, Magkos F, Bier DM, et al. Saturated Fats and Health: A Reassessment and Proposal for Food-Based Recommendations: JACC State-of-the-Art Review. J Am Coll Cardiol. 2020;76(7):844-857. doi:10.1016/j.jacc.2020.05.077 Hayes KC, Pronczuk A. Replacing Trans Fat: The Argument for Palm Oil With a Cautionary Note on Interesterification. J Am Coll Nutr. 2010;29(3 Suppl):253S-284S. doi:10.1080/07315724.2010.10719842 U.S. Department of Agriculture. ChooseMyPlate. Saturated, Unsaturated, and Trans Fats. Additional Reading Berry SE, Bruce JH, Steenson S, et al. Interesterified fats: What are they and why are they used? A briefing report from the Roundtable on Interesterified Fats in Foods. Nutr Bull. 2019;44:363-380. doi:10.1111/nbu.12397 Harvard T.H. Chan School of Public Health. The Nutrition Source. Shining the Spotlight on Trans Fats.