This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
It is very doubtful whether perfectly pure sugar is laxative; at least it can be but very slightly so; but, in the impure state in which we receive it from the cane, and in the form of molasses, it certainly has a tendency to operate gently on the bowels. The most laxative form of it is probably the kind of molasses which constitutes the residue after the crystallization of sugar from cane-juice, and with which we are supplied, in this country, chiefly from the plantations in Louisiana and the West indies That obtained from sugar-houses, which is the residue of brown sugar after refinement, and which is frequently called treacle, is next probably in laxative power; and brown or crude sugar is the least so of these three forms. They are useful as laxative articles of diet, in connection with bread, mush, etc., and in cases in which the digestive powers are vigorous. in a stomach enfeebled by dyspepsia or chronic gastritis, they are apt to undergo chemical change, generating acid, and causing unpleasant symptoms of gastric irritation, and sometimes sick-headache. They are specially adapted to cases of piles and prolapsus ani. The late Dr. Physick used to speak highly of the advantage, in the prolapsus ani of children, of a diet consisting of rye-mush and molasses.