Alimentary School: Learn 6 Amazing Facts From 'Gulp'

Why did Elvis Presley die sitting on the toilet?  Whose flatulence is worse, men's or women's? How many pints of saliva do we produce every day? What causes morning breath? What three foods are most likely to kill someone? Do prisoners really smuggle stuff in their rectums?

Science writer Mary Roach has examined something we do everyday -eat, chew, swallow, digest, defecate - and turned it into a rollicking, informative, downright funny explanation of  everything that happens in our digestive tract from teeth to tush. Her book, Gulp: Adventures on the Alimentary Canal, is fascinating and, yes, occasionally gross.

Roach has written other popular science books, including ones on corpses ( Stiff), sex ( Bonk) and outer space ( Packing for Mars), but this one is particularly fun - and fascinating - to read. It's also stomach-churning to learn what she did to gather some of this information, including undergoing a colonoscopy without sedation just so she could see what her insides looked like.

She also visits a lab that studies saliva (they collect your spit by having you chew a tampon), a professor who's an expert on flatulence and its various odors, and a prison to learn about the art of rectal smuggling.

So are you ready to digest some fascinating facts about digestion? Some nuggets from Roach's book:

Elvis Presley had intractable constipation, leading to a colon that was distended to twice to three times its normal size, according to his autopsy report. This may have led to his death from fatal arrhythmia as he strained to take care of business.

Morning breath is "hydrogen sulfide released by bacteria consuming shed tongue cells while you mouth-breathe for eight hours." During the day, saliva normally washes this debris away.

Foods most likely to kill someone by getting stuck in the throat or windpipe: "Hotdogs, grapes, and round candies take the top three slots in a list of killer foods published in the July 2008 issue of the International Journal of Pediatric Otorhinolaryngology, itself a calamitous mouthful."

Saliva - We generate two to three pints a day and it has healing and cleaning properties, in addition to helping get our food ready for digestion. Saliva contains amylase, an enzyme that helps break down starches into digestible energy. "Add a drop of saliva to a spoonful of custard, and within seconds it pours like water."

The rectum -  "Prison wallet" is the slang term - and it really does provide a way for some inmates to smuggle in things like cigarettes or cellphones, although Roach learns of one inmate who used it to smuggle in office supplies, including "two boxes of staples, a pencil sharpener, sharpener blades and three jumbo binder rings."

Whose flatulence is worse, men's or women's? Research reveals, Roach writes, that men are responsible for "a greater volume of gas per passage," while women's emissions were "deemed to have a significantly worse odour."

Photo: Cover of Gulp by Mary Roach, published by W.W.Norton & Company