A powdered thickening agent used in sauces and stews. Along with okra and roux, gumbo file (sometimes just called "file") produces the characteristic fullness of gumbo, one of the flagship dishes of cajun cooking.

The proper pronounciation is FEEL-ay (as in "play"). It may be spelled "filé," but the accent is usually omitted.

First used by the Choctaw Indians, file is is a drab green powder which superficially resembles powdered henna, and is produced by grinding the leaves of the sassafrass plant. It has a mild taste which is similar to root beer.

File dissolves quickly in water and has an effect similar to that of cornstarch or arrowroot. A small pot of gumbo, starting with one liter (~1 quart) of stock, may use up to one-half cup (120ml) of gumbo file. The quantity varies widely depending on the desired texture of the soup and the other ingredients used.

I have not been able to find nutritional information on file, but as a starch it probably has a profile similar to that of flour, around 360kcal/100g. It is much less dense than flour, so I can't reliably convert that to volume. It does not appear to contain any fiber.