As anyone who has fed a small child a large quantity of blueberries or who eats a lot of beets can tell you, some natural foods with strong colors pass unchanged through the digestive system.

For some people who eat beets, this has the alarming effect of turning their urine red. For others, the red coloring of beets makes it look like they have intestinal bleeding.

Glad I saw this before trying the beet hummus recipe in Run Fast, Eat Slow (I want to see if the hype about beets improving running performance is true.) Thanks for the heads up!