I love marshmallows. I especially like them after I've opened the bag to let them sit and get hard and stale for 4-6 months. They are a special treat then.
But I'm really skeptical about this:
Update: However, be sure to see the comment and check out the link there. And see this from Wikipaedia. Thanks to MA for the additional info:
Marshmallow probably came first into being as a medicinal substance, since the mucilaginous extracts come from the root of the marshmallow plant, Althaea officinalis, which were used as a remedy for sore throats. Concoctions of other parts of the marshmallow plant had medical purposes as well. The root has been used since Egyptian antiquity in a honey-sweetened confection useful in the treatment of sore throat. The later French version of the recipe, called pâte de guimauve (or "guimauve" for short), included an egg whitemeringue and was often flavored with rose water.
The use of marshmallow to make a sweet dates back to ancient Egypt, where the recipe called for extracting sap from the plant and mixing it with nuts and honey. Another pre-modern recipe uses the pith of the marshmallow plant, rather than the sap. The stem was peeled back to reveal the soft and spongy pith, which was boiled in sugar syrup and dried to produce a soft, chewy confection. Confectioners in early 19th century France made the innovation of whipping up the marshmallow sap and sweetening it, to make a confection similar to modern marshmallow. The confection was made locally, however, by the owners of small sweet shops. They would extract the sap from the mallow plant's root, and whip it themselves. The candy was very popular, but its manufacture was labour-intensive. In the late 19th century, French manufacturers thought of using egg whites or gelatin, combined with modified corn starch, to create the chewy base. This avoided the labour-intensive extraction process, but it did require industrial methods to combine the gelatin and corn starch in the right way.