Eating is the most pleasurable, gross, necessary, unspeakable biological process we undertake. But very few of us realise what strange wet miracles of science operate inside us after every meal - let alone have pondered the results (of the research). How have physicists made crisps crispier? What do laundry detergent and saliva have in common? Was self-styled `nutritional economist' Horace Fletcher right to persuade millions of people that chewing a bite of shallot seven hundred times would yield double the vitamins?

In her trademark, laugh-out-loud style, Mary Roach breaks bread with spit connoisseurs, beer and pet-food tasters, stomach slugs, potato crisp engineers, enema exorcists, rectum-examining prison guards, competitive hot dog eaters, Elvis' doctor, and many more as she investigates the beginning, and the end, of our food.