Though people have likely been reading on the toilet as long as there have been books and bathrooms, virtually no scientific work has been done to determine if reading on the can is a good idea or if doing it helps flush away your health. Fortunately, The Guardian has some answers:
It transpires that toilet readers spend more time on the loo and consider themselves less constipated than non-toilet readers, but other measures of their defecation habits show the two groups hardly differ. Shaoul's work hints that toilet readers suffer more hemorrhoids – something that made for cautionary news stories around the world – but the effect is negligible.But the miles it takes to come to this conclusion are interesting, including Henry Miller’s stylized toilet reading:
Miller went so far as to recommend toilets for individual authors. To enjoy Rabelais, he advised a plain country toilet, "a little outhouse in the corn patch, with a crescent sliver of light coming through the door". Better still, he said, take a friend along, to sit with you for half an hour of minor bliss.The full piece is here.