Until I started typing this entry, I had a vague feeling that some people's metabolisms could break down the chemicals in asparagus, and others could not, and therefore excreted them in urine, giving it a distinctive smell, and that this has been linked to a single gene.
However, I just stopped and read wikipedia, to double check the name of the chemical responsible (asparagusic acid) and discovered that scientific opinion has moved on.
In the 1980s three studies from France, China and Israel published results showing that producing odorous urine from asparagus was a universal human characteristic. The Israeli study found that from their 307 subjects all of those who could smell 'asparagus urine' could detect it in the urine of anyone who had eaten asparagus, even if the person who produced it could not detect it himself. Thus, it is now believed that most people produce the odorous compounds after eating asparagus, but only about 22% of the population have the autosomal genes required to smell them.So, that's interesting isn't it? I do have this gene, and I am currently entertained by the fragrance of asparagus whenever I go to the loo.