Trans fatty acids, commonly known as trans fats, are a type of unsaturated fat that became a public health concern due to their widespread presence in processed foods and detrimental health effects. The food industry once favored these fats for enhancing food texture, stability, and shelf life. However, scientific research has revealed a clear link between trans fat consumption and various adverse health outcomes, leading to global efforts to reduce and eliminate artificial trans fats from the food supply.
What are Trans Fatty Acids
Fatty acids are organic molecules that serve as building blocks for fats in the body and in food. The chemical structure of fatty acids includes a chain of carbon atoms. When a fatty acid contains double bonds between carbon atoms, it is considered unsaturated. The arrangement of hydrogen atoms around these double bonds determines whether the fatty acid is a “cis” or “trans” configuration.
In a “cis” configuration, the hydrogen atoms on either side of the double bond are on the same side of the carbon chain, causing a bend or kink in the molecule. This bent shape prevents the fatty acid molecules from packing tightly together, resulting in fats that are typically liquid at room temperature, like most vegetable oils. Conversely, in a “trans” configuration, the hydrogen atoms are on opposite sides of the double bond, leading to a straighter, more linear molecular shape. This linear structure allows trans fatty acid molecules to pack more closely, giving them properties similar to saturated fats, such as being solid or semi-solid at room temperature.
There are two main types of trans fatty acids: artificial and naturally occurring. Artificial trans fats, also known as partially hydrogenated oils (PHOs), are created through a process called partial hydrogenation. This industrial process involves adding hydrogen to liquid vegetable oils, which converts some of the unsaturated bonds from a cis to a trans configuration, making the oil more solid and extending its shelf life.
Naturally occurring trans fats are found in small amounts in meat and dairy products from ruminant animals such as cows, sheep, and goats. These are formed in the animals’ digestive systems through a natural process called biohydrogenation. While both types of trans fats have the “trans” configuration, artificial trans fats from partially hydrogenated oils have been the primary focus of public health concerns due to their widespread presence in processed foods and their established adverse health effects.
Common Sources of Trans Fatty Acids
Artificial trans fatty acids, primarily originating from partially hydrogenated oils, were once widely used in the food industry due to their stability, texture-enhancing properties, and cost-effectiveness. These industrially produced fats were prevalent in a variety of processed food items designed for extended shelf life and appealing textures.
Common sources included:
Baked goods: Cookies, cakes, pies, pastries, and biscuits often used partially hydrogenated shortenings, contributing to desired flakiness and structure.
Fried foods: Doughnuts, french fries, and fried chicken frequently used partially hydrogenated oils for deep-frying, as these oils could be reused multiple times in commercial fryers without breaking down quickly.
Snack foods: Crackers, microwave popcorn, and some pre-packaged convenience meals.
Margarines and vegetable shortenings: Particularly stick varieties, were major sources.
Restaurants and fast-food establishments historically relied on partially hydrogenated oils for frying and baking due to their stability and ability to withstand high temperatures, which made them economical for large-scale food preparation. While natural trans fats are present in small quantities in meat and dairy products from ruminant animals, these naturally occurring forms are not considered the primary public health concern. The focus remains on the artificial trans fats produced through industrial processes, which have been largely removed from the food supply in many regions due to regulatory actions.
Health Impacts
The consumption of artificial trans fatty acids has been strongly linked to several adverse health effects, particularly impacting cardiovascular health. One of the primary concerns is their detrimental effect on cholesterol levels. Trans fats raise levels of low-density lipoprotein (LDL) cholesterol, often referred to as “bad” cholesterol, which contributes to the buildup of plaque in arteries. Simultaneously, they lower levels of high-density lipoprotein (HDL) cholesterol, known as “good” cholesterol, which helps remove cholesterol from the arteries. This dual effect on cholesterol markers significantly increases the risk of developing coronary heart disease, stroke, and other cardiovascular conditions.
Research indicates that an increased intake of trans fat, even exceeding 1% of total energy intake, is associated with a higher risk of coronary heart disease mortality and events. High trans fat intake has been shown to increase the risk of death from any cause by 34% and the risk of coronary heart disease death by 28%. It is estimated that trans fatty acid intake is responsible for over 500,000 premature deaths from coronary heart disease annually worldwide.
Beyond cardiovascular disease, trans fats also play a role in promoting systemic inflammation within the body. Chronic inflammation is a factor in the development and progression of various chronic diseases. Some studies have also suggested a potential link between trans fat consumption and an increased risk of developing type 2 diabetes, further highlighting their broad negative impact on metabolic health.
Identifying and Avoiding Trans Fats
To reduce or eliminate trans fats from your diet, understanding how to identify them on food labels is paramount. The most effective strategy is to look for “partially hydrogenated oil” in the ingredient list. Even if a product’s nutrition facts panel states “0 grams of trans fat,” it can still contain small amounts if the serving size has less than 0.5 grams of trans fat per serving, due to labeling regulations. Therefore, checking the ingredient list for partially hydrogenated oils provides a more accurate assessment.
Opting for healthier fat alternatives is another practical approach. Replacing foods high in artificial trans fats with sources of unsaturated fats, such as olive oil, canola oil, and avocado oil, can contribute to better health outcomes. Incorporating nuts, seeds, and lean proteins into your diet also provides beneficial fats and nutrients. Preparing meals at home offers greater control over ingredients, allowing you to avoid hidden sources of trans fats commonly found in commercially processed and fried foods.
Regulatory actions have significantly impacted the availability of artificial trans fats. In 2015, the U.S. Food and Drug Administration (FDA) determined that partially hydrogenated oils (PHOs), the primary dietary source of artificial trans fats, were no longer “Generally Recognized As Safe” (GRAS) for use in human food. This determination effectively led to a ban on PHOs in the U.S. food supply, with compliance dates set for June 18, 2018, and an extended compliance for certain uses until January 1, 2020. This regulatory shift underscores the recognized health risks associated with artificial trans fats and provides a safer food environment for consumers.