Asparagus, pee and your nose

The other night I peed in the shower (it's all pipes) and it smelled terrible, like a cabbage and rotten egg omelet. My thoughts naturally jumped to urinary tract infection or bladder cancer, but then I remembered that we had steamed asparagus with our salmon and realized I was experiencing the infamous asparagus pee. It was my first experience with smelly pee (although we regular eat asparagus) and I decided to do a little digging to see what was going on inside my body.

The more I look for answers to my food questions the less faith I have in the scientific community. Like many things that have to do with chemicals and the body, scientists are not exactly sure why asparagus makes your pee smell. Today the main suspects in this mystery are the chemical compounds S-methyl thioesters and methanethiol. The thought is that when your digestive tract breaks down one or both of these compounds (or some other compound, who knows) another smelly compound is produced as the byproduct.

There other side of the asparagus mystery concerns those who can produce the smell and those who can smell it. Theory 1: Everyone can produce the stinky pee, but not everyone can smell it because a special autosomal gene is required to sense the stench. Theory 2: Conversely, everyone possesses the gene to smell the smell but not everyone's digestive system can produce the smell. There have been some corroborating studies for Theory 1. From the studies subjects all of those who could smell the unpleasant urine could detect it in the pee of anyone who had eaten asparagus, even if the person who produced it could not detect it himself. I wonder how much the participants of the study got paid to eat a plate of asparagus, pee in a cup and smell hundreds of urine samples?

These theories are all well and good, but why after years of eating asparagus and peeing am I just now smelling it? Has my body mutated and developed the gene to produce smelly pee, smell the smelly pee, or both? It's enough to make your head spin, gotta love science.