The U.S. Food and Drug Administration this week announced a preliminary determination that partially hydrogenated oils (PHOs), the primary dietary source of artificial trans fat in processed foods, are not “generally recognized as safe” for use in food.

Trans fat, according to Wikipedia, is the common name for unsaturated fat with trans-isomer fatty acid. Trans fats are sometimes monounsaturated or polyunsaturated, but never saturated. Trans fats occur during the processing of polyunsaturated fatty acids in food production. Artificial trans fat is created when hydrogen is added to vegetable oil (a process called hydrogenation) to make it more solid. Food manufacturers use partially hydrogenated oils to improve the texture, shelf life and flavor stability of foods.

Health concerns in the past focused primarily on saturated fats, but in recent years the health community has come to view PHOs or trans fats as a greater health threat. Consumption of trans fat raises low-density lipoprotein (LDL), or “bad” cholesterol, increasing the risk of coronary heart disease.

Food companies and U.S. consumers have been cutting back on trans fats for some time. Trans fat content information began appearing in the Nutrition Facts label of foods in 2006, and according to the FDA, trans fat intake among American consumers has declined from 4.6 grams per day in 2003 to about 1 gram per day in 2012.  However, some processed foods such as certain desserts, microwave popcorn products, frozen pizzas, margarines and coffee creamers still contain trans fats. FDA Commissioner Margaret A. Hamburg, MD, believes further reduction in the amount of trans fat in the American diet could prevent an additional 20,000 heart attacks and 7,000 deaths from heart disease each year.

The agency has opened a 60-day comment period on the preliminary determination to collect additional data and to gain input on the time food companies would need to eliminate trans fats from their products.  Following a review of the submitted comments, if the FDA finalizes its preliminary determination, PHOs would be considered “food additives” and could not be used in food unless authorized by regulation.

If such a determination were made, the agency would provide adequate time for producers to reformulate products in order to minimize market disruption. The FDA’s preliminary determination is only with regard to PHOs and does not affect trans fat that naturally occurs in small amounts in certain meat and dairy products. Read more from the FDA, including instructions for submitting comments.