Hedging is the use of tentative lexis or grammar to lessen the definitiveness of a statement. It can be used to add a tentative tone to a statement, thus making it less direct and more polite - eg instead of saying Go and see a doctor!, saying You might find it useful to talk to a doctor.
Hedging is a common feature of academic style where it is used to avoid making definitive statements that could be disproved by a better-informed reader or by future research. So instead of saying : Antispasmodics act by reducing colonic contraction and transit time the writer of a paper in a medical journal might say eg : Smith and Brown (2010) have suggested that antispasmodics may act by reducing colonic contraction and transit time.
Citation of the source takes the final responsibility away from the writer of the paper, while the use of the verb suggest and the modal of possibility may mean that if it is later proved not to be true, the writer can't be accused of giving false information.