Black Burger, Green Poop: Halloween Meal's Odd Effects Explained

Burger King recently introduced its Halloween Whopper — the restaurant's signature hamburger is sporting a black bun during October. "Sometimes stool color is very important, and sometimes we can get worried inappropriately about the color of stool," Dr. Ian Lustbader, a clinical associate professor of medicine and a gastroenterologist at New York University's Langone Medical Center, told Live Science. Most likely, it's the food coloring in the bun, Lustbader said.