If you've eaten asparagus, you have probably smelled it. But if you are one of those who can eat asparagus without later experiencing sulfur-scented pee, is it because you can't smell it or because your pee really is asparagus odor-free?

A new study says either scenario could be true. The researchers also identified a single variation in the DNA code associated with a person's sensitivity to the smell of asparagus pee.