The invention relates to compositions for use in purgatives, to purgatives comprising such compositions, and to methods for inducing purgation of the colon. The composition may comprise at least one water-soluble sodium salt; at least one water-soluble minimally degradable sugar in an amount, by weight, of from about 1 to about 3 times the weight of sodium ions in said composition; at least one water-soluble potassium salt in an amount, by weight, of from about 0.05 to about 1 time the weight of said sodium salt in said composition; and at least one water-soluble magnesium salt, wherein the weight of magnesium ions in said composition is from 0.1 to about 10 times the weight of sodium ions in said composition.