Cats are well-known for being fussy eaters, always demanding the freshest, tastiest foods. But occasionally a cat will go to the other extreme and begin snacking in the most unappetizing of places, the litter box.

Eating litter isn't necessarily dangerous, although cats that take more than a small nibble may get obstructions in their intestinal tracts. The real problem isn't the litter lunch itself but the underlying condition that is causing them to take up the habit.

"A cat that suddenly starts eating litter is almost always sick," says Jane Brunt, D.V.M., a veterinarian in private practice in Towson, Maryland. For example, cats with anemia, a condition in which the body doesn't have enough red blood cells, will sometimes eat litter. Vets aren't sure why they do it, but it may be nature's way of getting more iron into their systems. Cats with kidney disease or feline leukemia will also eat litter on occasion, she says.

"Cats with poor diets, especially those given vegetarian diets, may crave nutrients," adds Carol A. Tice, D.V.M., a veterinarian in private practice in Cary, North Carolina. The clay used to make litter is rich in minerals and may act as a natural supplement. Cats that keep eating litter, however, may actually lose nutrients because the clay will leach out more minerals like iron, zinc, and potassium than it puts back in.