Question: Are women’s farts smellier than men’s?
Short answer: No.
Long answer: A famous paper by Suarez, Springfield, and Levitt (Gut, 1998) is often touted as evidence that women’s farts are smellier than men’s. Strangely, websites often describe the findings as “new”, even though they are over 20 years old.
The paper does not actually reach the conclusion that women’s farts are smellier than men’s. The authors collected fart smell via a tube inserted into each subject’s rectum. The gas that was captured was analyzed objectively by chromatographic-mass spectroscopy and subjectively by two judges with experience in detecting sulfur compounds by smell. The conclusion is worth quoting at length:
“Although highly variable, the flatus of women had a significantly greater concentration of hydrogen sulphide and was deemed to have a significantly worse odour by both judges. However, in practice, the ability of malodorous flatus to stimulate the nose is a function of the volume (as opposed to the concentration) of noxious gases in an individual passage. Because men tended to have greater volumes of gas per passage, no significant gender differences were observed for sulphur gas volume per passage.”
In short, women’s farts have greater concentrations of hydrogen sulfide, but men’s farts are bigger. Since both factors are important for the diffusion of farts, it seems safe to say that the total amount of stink delivered per fart is about equal for men and women. The paper does not say much more than that, as the aims of the study had nothing to do with sex differences in fart smell.
Moreover, while the method of collection in that experiment was highly controlled, including the food consumed by the participants (pinto beans), the authors acknowledge that the sample size was actually quite low. The total number of farts was just 87 (52 from men and 35 from women). So it remains an open question whether fart smell differs between men and women.
We have attempted to address this question, using our extensive fart database. Unfortunately, our sample of female farts is also quite limited, with the total being 59. For comparison, we have collected 1564 male farts with the same apparatus, and these comprise 96.36% of the data. The reason for this sampling bias likely has to do with the social psychology of flatulence, which is quite interesting, but not something we can address with our data.
In any case, our results are plotted here, using log VOC levels as our standard measure of smelliness:
Both sexes have the characteristic bimodal distribution of fart smells, but importantly these distributions are rather different. The median smelliness for ladies is 2.56 ppm, while for gentlemen it is 5.07 ppm. Thus, in our data, the average male fart is twice as smelly as the average female fart.
The difference between these results and those of Suarez et al. (1998) probably reflects the different methods of data collection. In particular, our approach measures fart smell as it reaches the open air, which depends on both the concentration at the source and its propulsion into the surrounding environment. In this regard, the more voluminous male farts might be more detectable to a nearby observer, despite having lower concentrations of malodorous chemicals.