$666 burger? A New York City food truck is selling a $666 hamburger dubbed the "Douche Burger," which contains lobster, caviar, truffles, and a beef patty wrapped in six sheets of gold leaf. How much gold leaf can you safely consume?

Theoretically, you could eat your fill of 24-karat gold without falling ill. Pure gold is chemically inert and passes through the human digestive system without being absorbed into the body.

Since 24-karat gold is very soft and fragile, most edible gold—whether leaf, flakes, or dust—also contains a little bit of silver, which is also inert.

Non-edible gold leaf, which is used for gilding, sometimes contains copper, which can be toxic in high doses. Go here to read more and see a photo.