(Recasts first sentence; adds details from conference call, comments from FDA commissioner and health advocate, background)
BOSTON/WASHINGTON, Nov 7 (Reuters) - The U.S. Food and Drug Administration on Thursday proposed banning artificial trans fats in processed food ranging from cookies to frozen pizza, citing the risk of heart disease.
Partially hydrogenated oils, which are the primary dietary source of the fats, have been shown to raise "bad" cholesterol. Reducing the use of trans fats could prevent 20,000 heart attacks and 7,000 deaths from heart disease a year, the FDA said.
"While consumption of potentially harmful artificial trans fat has declined over the last two decades in the United States, current intake remains a significant public health concern," FDA Commissioner Margaret Hamburg said.
Public health advocates welcomed the move.
"Artificial trans fat is a uniquely powerful promoter of heart disease, and today's announcement will hasten its eventual disappearance from the food supply," Michael Jacobson, executive director of the non-profit Center for Science in the Public Interest said.
The FDA's proposal is not the first public effort to ban trans fats. New York City banned the use of trans fats in restaurants, and many restaurants and fast food chains, including McDonald's Corp., have eliminated them.
Trans fats are present in a wide range of processed foods including crackers and cookies, frozen pizza and refrigerated dough, coffee creamers and ready-to-use frosting.
Some products will be harder to reformulate than others, FDA officials said.
"We know that technically this is not an insoluble problem," Hamburg told reporters on a conference call, adding that the use of trans fats has declined dramatically since 2006, when the agency required companies to disclose trans fat levels on package labels.
According to the Grocery Manufacturers Association, food manufacturers have voluntarily lowered the amounts of trans fats in their food products by more than 73 percent.
Partially hydrogenated oils are derived from vegetable oils such as soybean. Hydrogenation, a chemical process, converts liquid vegetable oils into solid or semi-solid fats, which are preferred for baking and have a longer shelf life.
The FDA's proposal is subject to a 60-day public comment period in which food companies are expected to outline how long they expect it to take them to reformulate products.
If the proposal becomes final, partially hydrogenated oils would be considered food additives and would not be allowed in food unless authorized by health regulators. The ruling would not affect naturally occurring trans fat that occurs in small amounts in certain meat and dairy products.
Companies wishing to include trans fats in their products would have to meet the safety standards applied to food additives and prove with reasonable certainty that they do not cause harm.
"GENERALLY RECOGNIZED AS SAFE"
It has been more than half a century since U.S. regulations governing food additives were last revised. In that time, the number of chemicals in the food supply has risen from fewer than 2,000 to an estimated 10,000, many of which are never reviewed by the FDA because companies and their advisers have declared them to be safe.
Under loose regulations created more than 50 years ago to help companies avoid lengthy delays in getting food additives approved, the FDA created a list of products considered "generally recognized as safe" (GRAS).
Companies can either petition to get their ingredients affirmed safe by the FDA, or they can declare them safe based on their own research or that of hired consultants. The FDA has the option to challenge such declarations but has rarely done so.
The FDA's Hamburg said in an interview on Thursday that while the GRAS system provides the current legal framework for regulating food additives, the system bears re-examining to see if it is adequate to ensure the safety of the food supply.
"We do need to be thinking about what is needed to update laws and processes," she said.
The dominant vegetable oil used in the United States is soybean oil. The FDA's announcement sparked a rapid sell-off in Chicago soyoil futures prices by creating uncertainty about the impact on vegetable oil demand.
Soyoil futures fell 1.75 percent to 40.42 cents per pound in midday trading.
(Reporting by Toni Clarke and Ros Krasny; Editing by Andrea Ricci, Marguerita Choy and Leslie Adler)