Asparagusuria

Very little scientific research seems to have been devoted to why and what makes asparagus consumption result in the person having smelly urine in some cases, and not in other people's cases. Of the little research regarding asparagusuria found in Pubmed, the points made are contradictory, but for now it may be prudent to go with the conclusions based mostly on research by Mitchell and Waring, since they have done the most, but also take the few other papers into consideration. The observations were :

1. The smelly urine is a genetic autosomal dominant rule. Meaning they suggest you only need one 'copy' of the responsible gene for the condition to occur. This is the opposite of what the medical books generally regard TMAU (autosomal recessive. Meaning you need 2 bad copies). If it turned out 'bloodborne odors' was autosomal dominant, it would bring in a lot more people into the equation of having bloodborne body odor. It does seem that one or more TMAU experts probably do now feel that 'transient' TMAU is likely to be autosomal dominant, given some of the papers on pubmed, although it doesn't seem to be a current official 'rule'.

2. About 40% (in one study) were regarded as being unable to smell the urine whether it was theirs or anyone elses (non-perceivers)

3. there are 3 possible outcomes:
no smell from the urine (the smelly metabolites are not there - non-excretors)
the urine smells (excretors)(in about 8% of the UK Caucasian population it is super-smelly, since they have 2 copies of the excretor gene - homozygous)
the urine smells but the sufferer can't smell it (excretors but non-perceivers).
However, none of the above outcomes is 'official', since the few papers give contradictory outcomes.

There is the possibility that the asparagusuria urine test could be a cheap test for potential bloodborne body odor cases, but this must currently be considered unlikely. Possibly the bloodborne BO cases would be the super-smelly urine cases, with them also being unable to smell their own urine, same as what seems to happen in most bloodborne BO cases. An expert suggested that one possibility is that those who excrete super-smelly urine may be 'non-perceivers' because their smell receptors could be already saturated.

Overall, nothing can be deduced from this post in connection to bloodborne body odor/halitosis, and it is posted only as something to think about.

pubmed asparagus odor urine search
Mitchells last paper (2001) on Asparagusuria
Interesting comments on Wisegeek.com

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note : the inabilty to smell asparagus urine is not taken into account in the polls