The showdown between butter and margarine has been whipping up debate for decades.

Unilever recently started adding butter to one of the brands of margarine it sells in Europe while in the United States, overall butter consumption is up, and margarine sales are on the decline.

Sylvain Charlebois, a marketing professor at the University of Guelph in Ontario, called Unilever's move "a mea culpa."

“They’ve been battling this butter war for years and now they’re looking at market data, and it’s pretty obvious that market shares for butter are increasing and sales for margarine are decreasing,” he said on CBC Regina’s Morning Edition. “So they’re trying to capitalize on some momentum here, and butter seems to be the preferred choice for many consumers now.”

Click on the "Battle of the spreads" link on the left to hear more of the discussion.

Sources: USDA Economic Research Service, Canadian Dairy Information Centre