The one type of fat that nutrition experts agree should be limited in all diets is artificial trans fat. Unlike other dietary fats, such as saturated or unsaturated fats, which have a role in the body’s function and simply require moderation, artificial trans fats offer no known nutritional benefit. The consensus is that any amount of this industrially produced fat poses a risk to health, making its elimination a universal goal for healthy eating.
The Fat Universally Targeted for Limitation
The fat primarily targeted for limitation is the industrially produced form of trans fatty acids, which is chemically distinct from the small amount of natural trans fat found in the meat and dairy of ruminant animals. These artificial trans fats are created through a process called partial hydrogenation, where hydrogen is added to liquid vegetable oils to change their chemical structure. This process makes the oil semi-solid at room temperature, converting it into what is known as partially hydrogenated oil (PHO).
Food manufacturers initially adopted this process because it was inexpensive and gave products desirable characteristics. Partial hydrogenation extended the shelf life of processed foods and offered the texture and consistency needed for commercial baking and frying, such as in shortening and hard margarine. Historically, PHOs were widely used in a variety of foods because they were cheaper and more stable than traditional animal fats.
While natural trans fats from animal sources make up a small portion of the diet and do not show the same negative health associations, the industrial form is widely recognized as uniquely harmful. The goal of a healthy diet is to reduce the intake of artificial trans fats to the lowest possible level, ideally zero.
Mechanisms of Harm: Why This Fat Is Detrimental
The primary reason artificial trans fats are universally detrimental is their severe, two-fold negative impact on cardiovascular health, affecting the body’s cholesterol profile. This fat not only elevates levels of low-density lipoprotein (LDL) cholesterol, often referred to as “bad” cholesterol, but also simultaneously lowers levels of high-density lipoprotein (HDL) cholesterol, the “good” cholesterol. This double effect creates a significantly higher risk for the development of atherosclerosis, which is the buildup of plaque in the arteries.
The presence of artificial trans fats in the diet also promotes systemic inflammation, which is a significant factor in the progression of heart disease. These fats interfere with the body’s normal metabolic processes, affecting the structure of cell membranes and potentially impairing the ability of blood vessels to relax, a function known as endothelial function. This disruption to the lining of the blood vessels further contributes to the risk of heart attacks and strokes.
These metabolic disruptions are not dependent on an individual’s physical activity level or general health status, which is why the limitation applies to all diets, from athletes to the general population. The chemical structure of these industrially altered fats makes them difficult for the body to process correctly, leading to a cascade of negative effects that increase the risk of coronary heart disease. Clinical studies have confirmed that the consumption of industrial trans fatty acids is strongly associated with a higher risk of cardiovascular events.
Practical Avoidance: Identifying Sources and Reading Labels
A number of common foods historically contained artificial trans fats because of the use of partially hydrogenated oils. These sources include commercially baked goods like cakes, cookies, crackers, and pies, as well as many fried foods such as doughnuts and fried chicken. Other typical sources are frozen pizza, refrigerated dough, certain coffee creamers, and stick margarines. Although regulatory efforts have greatly reduced their presence, consumers must remain vigilant.
The United States Food and Drug Administration (FDA) has largely banned the use of partially hydrogenated oils (PHOs), the main source of artificial trans fat, by revoking their “Generally Recognized as Safe” status. This action has substantially eliminated PHOs from the food supply, with the final compliance date for manufacturers being January 2021. The FDA estimated that removing PHOs could prevent thousands of heart attacks and deaths each year.
Consumers can identify hidden trans fats by carefully reading the ingredient list, even if the nutrition facts panel lists “0 grams trans fat”. Food manufacturers are legally allowed to claim zero grams of trans fat per serving if the product contains less than 0.5 grams. This “rounding rule” means that if a person eats multiple servings, they may still consume a significant amount of the fat. The most reliable way to ensure a product is free of artificial trans fats is to check the ingredient list for the phrase “partially hydrogenated oils”. If this term appears anywhere in the ingredients, the product contains artificial trans fats and should be avoided.