Trans fats are a form of unsaturated fat. There are two types — natural and artificial trans fats. Natural trans fats are formed by bacteria in the stomach of cattle, sheep and goats. These trans fats make up 3–7% of the total fat in dairy products, such as milk and cheese, 3–10% in beef and lamb and just 0–2% in chicken and pork (1, 2). On the other hand, artificial trans fats are mainly formed during hydrogenation, a process in which hydrogen is added to vegetable oil to form a semi-solid product known as partially hydrogenated oil.
Studies have linked consumption of trans fats to heart disease, inflammation, higher “bad” LDL cholesterol and lower “good” HDL cholesterol levels (3, 4, 5, 6). Though evidence is limited, natural trans fats appear less harmful than artificial ones (7, 8, 9). Though the FDA’s ban of trans fats went into effect on June 18, 2018, products manufactured before this date can still be distributed until January 2020, or in some cases 2021 (10). Additionally, foods containing less than 0.5 grams of trans fats per serving are labeled as having 0 grams of trans fats (11). Therefore, while food companies are reducing the trans fat content of their products, a number of foods still contain artificial trans fats. To reduce your intake, it’s best to read ingredients lists carefully and limit your intake of the products listed below (12).
Here are 7 foods that still contain artificial trans fats.
1. Vegetable Shortening
Shortening is any type of fat that is solid at room temperature. It’s often used in cooking and baking. Vegetable shortening was invented in the early 1900s as a cheap alternative to butter and is typically made from partially hydrogenated vegetable oil. It is popular for baking due to its high fat content, which produces a softer and flakier pastry than other shortenings like lard and butter. In recent years, many companies have reduced the amount of partially hydrogenated oil in their shortening — making some shortening trans-fat-free.
However, it can be difficult to tell if a shortening is completely free of trans fats, as companies are allowed to list 0 grams of trans fat as long as a product has less than 0.5 grams per serving (11).
To find out if shortening contains trans fat, read the ingredients list. If it includes partially hydrogenated vegetable oil, then trans fats are present as well.
SUMMARY; Vegetable shortening made from partially hydrogenated oil was invented as a cheap substitute for butter. However, due to its high trans fat content, most manufacturers have now reduced or totally eliminated trans fats.
2. Some Varieties of Microwavable Popcorn
Air-popped popcorn is a popular and healthy snack food. It’s full of fiber but low in fat and calories. However, some varieties of microwavable popcorn harbor trans fats. Food companies have historically used partially hydrogenated oil in their microwavable popcorn due to its high melting point, which keeps the oil solid until the popcorn bag is microwaved. Notably — due to the recognized health risks of trans fat — many companies have switched to trans-fat-free oil in recent years.
If you prefer microwavable varieties, choose brands and flavors that don’t contain partially hydrogenated oil. Alternatively, make your own popcorn on the stovetop or in an air popper — it’s simple and cheap.
SUMMARY; Popcorn is a healthy, high-fiber snack. However, some varieties of microwaveable popcorn hold trans fats. To avoid trans fats, refrain from store-bought popcorn made with partially hydrogenated vegetable oil — or make your own.
3. Certain Margarines and Vegetable Oils
Some vegetable oils may contain trans fats, especially if the oils are hydrogenated. As hydrogenation solidifies oil, these partially hydrogenated oils were long used to make margarine. Therefore, most margarines on the market were high in trans fats. Fortunately, trans-fat-free margarine is increasingly available as these oils are phased out. However, keep in mind that some non-hydrogenated vegetable oils may also contain trans fat.
Two studies that analyzed vegetable oils — including canola, soybean and corn — found that 0.4–4.2% of the total fat content was trans fats (13, 14).To reduce trans fat consumption from margarine and vegetable oils, avoid products that contain partially hydrogenated oils or choose healthier oils such extra virgin olive oil or coconut oil.
SUMMARY; Partially hydrogenated oils contain trans fats. To reduce your trans fat intake, avoid all vegetable oils and margarines that list partially hydrogenated oil on the ingredient list — or use other cooking fats, such as butter, olive oil or coconut oil.
4. Fried Fast Foods
When eating on the go, bear in mind that trans fats may lurk in certain takeout options. Fried fast foods, such as fried chicken, battered fish, hamburgers, french fries and fried noodles, can all hold high levels of trans fat. The trans fats in these foods can come from a few sources. Firstly, restaurants and takeaway chains often fry foods in vegetable oil, which can contain trans fats that soak into the food (13, 14). Furthermore, high cooking temperatures used during frying can cause the trans fat content of the oil to increase slightly. The trans fat content increases each time the same oil is reused for frying (15, 16). It can be hard to avoid trans fats from fried food, so you are better off limiting your intake of fried food altogether.
SUMMARY; Fried foods, such as french fries and hamburgers, are often cooked in vegetable oils, which may harbor trans fats. Furthermore, the trans fat concentration increases each time the oil is reused.
5. Bakery Products
Bakery goods, such as muffins, cakes, pastries and doughnuts, are often made with vegetable shortening or margarine. Vegetable shortening helps produce a flakier, softer pastry. It’s also cheaper and has a longer shelf life than butter or lard. Until recently, both vegetable shortening and margarine were made from partially hydrogenated oils. For this reason, baked goods have traditionally been a common source of trans fat. Today, as manufacturers reduce the trans fat in their shortening and margarine, the total amount of trans fats in baked goods has similarly declined (12). However, you can’t assume that all baked foods are free from trans fat. It’s important to read labels where possible and avoid pastries that contain partially hydrogenated oils.
Better still, make your own baked foods at home so that you can control the ingredients.
Bakery products are often made from vegetable shortening and margarine, which were previously high in trans fats. Most companies have reduced the trans fat content in these products, resulting in less trans fat in baked goods.