The European horse meat scandal continues to expand: This week, the Switzerland-based company Nestle SA announced that it would pull beef pasta meals off supermarket shelves in Europe after the discovery that they contained horse meat. Most U.K. supermarkets had already been forced to pull what were ostensibly beef products after the discovery that they contained horse meat, and regulators are now trying to trace how the horse meat made its way through a complicated supply chain into various products.

So far, Americans have not been touched directly by the scandal, since the companies involved do not export beef to the United States. But the anger over the discovery has raised the question: Why is eating horse meat considered taboo in some nations yet unremarkable in others?

In the United States, United Kingdom and some other nations, horse meat is largely reviled. Asked to explain why she would not eat horse meat, New York City resident Victoria Milton compared them to pets, saying that "people have horses and they love them and they're part of their family."

In many other nations, however, eating horse meat is no big deal - and in some cultures, it's even considered a delicacy. Mexico, Switzerland, Kazakhstan, Belgium, Japan, Germany, Indonesia, Poland and China are among the nations where many people eat horse meat without a second thought.

There was a time when Americans did not have quite so much compunction about eating horse: A World War II-era photograph published by the Seattle Times in 2010 shows men holding a sign advertising "U.S. GOVERNMENT INSPECTED HORSE MEAT - NOT RATIONED." Those two words at the end are key: While beef was being rationed by the government at the time, horse meat was not. In the 1940s and 1950s, according to New York University professor of Food Studies Marion Nestle, there was a de facto "black market" for horse meat in which people would go into pet food stores to buy horse meat for their own consumption, viewing it as an inexpensive and tasty alternative to beef.

Anne Bellows, a professor of food studies at Syracuse University, said that food taboos "adjust themselves to circumstances." She argued that when cultures are facing hard times, taboos tend to go out the window. "Sometimes the choices we make are related to how needy we are," she said.

Horse meat was once a primary ingredient in pet food. In the 1920s, according to Nestle, slaughterhouses opened pet food companies to dispose of horse meat. It remained a major ingredient in pet food until at least the 1940s. Today, Nestle said, most pet food companies do not profess to use horse meat, partially for fear it would discourage people from buying the product.

While Americans have largely avoided horse meat except in lean times, U.S. plants were slaughtering horses for food as recently as 2006. More than 100,000 horses were slaughtered for food that year, mostly for export to Europe and Asia. The United States soon after effectively banned slaughtering horses for food by preventing tax dollars from being spent on horse meat inspection. (The ban lapsed in 2011, but no money has been allocated for new inspections.) Against the wishes of animal rights activists, horses are still being shipped to Canada and Mexico for slaughter and, in many cases, human consumption.