Asparagus contains a sulphurous compound called MERCAPTAN which is also found in rotten eggs, onions and garlic. [Dr Margaret Stern – ‘The Must Have Health Guide abort embarrassing conditions].  When your digestive system breaks down mercaptan, the by products cause a strange odour.  The process is so quick that this can affect the urine within 15 minutes of eating the asparagus.  But not everyone suffers; only some people have the gene that produces the enzyme that breaks mercaptan down into its more pungent constituents.