A U.S. plan to ban artificial trans fats in processed foods could hit demand for as much as 15 percent of the nation's edible soyoil, an industry official estimated on Thursday, although analysts saw a limited market impact as use has already fallen sharply.

The U.S. Food and Drug Administration on Thursday proposed banning the fats in foods ranging from cookies to frozen pizza, citing the risk of heart disease. The fat is used to help extend the shelf life or improve the taste or texture of some foods.

The oilseed and food-processing industries have been in the process of phasing out trans fats for several years, reducing consumption of hydrogenated soyoil to around 2 billion pounds, or about 15 percent of total consumption of edible soyoil, said Richard Galloway, a consultant to the United Soybean Board. That's down from 50 percent as recently as 2005, he said.

"At this point, a lot of the impact on the consumption of soybean oil has already occurred," said Anne Frick, senior oilseeds analyst with Jefferies Bache in New York.

Benchmark CBOT December soyoil futures on Thursday settled at 40.74 cents per pound, down 0.40 cent, about 1 percent, paring losses after tumbling in volatile trade to 40.28 cents, the contract's lowest level since Oct. 14. The daily limit in CBOT soyoil futures <0#BO:> is 2.5 cents per pound.

"I don't think this is any shock to the edible oil community. If it were, we'd be down the limit today, not 33 points," said Rich Feltes, vice president of research for R.J. O'Brien.

Joe Davis, a vice president with Futures International in Chicago, estimated that the FDA's proposal, if approved, would remove demand for about 400 million lbs of soyoil.

The U.S. Department of Agriculture estimated soyoil used for food, feed and industrial use (other than biodiesel fuel) in the 2012/13 marketing year ended Sept. 30 at 13.95 billion pounds.

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 since 2005. The FDA said the average daily intake of trans fats by Americans fell from 4.6 grams in 2003 to 1 gram in 2012.

Boon for Palm or Canola?

Nonetheless, alternative vegetable oils such as palm oil and canola could see increased demand as replacements for partially hydrogenated soyoil, traders and analysts said.

"Palm oil is the largest globally traded edible oil today, and so I would think you would see substitution into these other edible oils," said David Lehman, the CME Group's managing director of commodity research and product development.

"If there's some restriction that affects soybean oil more so than the other edible oils, then you would probably see substitution in the food manufacturing industry to those other oils," Lehman said.

Such substitution can take time.

"It isn't just a matter of taking out partially hydrogenated soy and plopping in palm oil or high-oleic canola. You might change the flavor profile significantly, and that is something food companies don't like to do," said Galloway.

"Food companies take about two years from the time they are introduced to an alternative ingredient until they can commit to a switchover," Galloway said.

Restaurants also may have to adjust, if trans fats are banned.

"This should be a warning that, if you haven't taken them off the menu, now is the time," said David Maloni, chief commodity analyst at the American Restaurant Association.