The adage says that tastes and colors cannot be discussed. However, when it comes to flatulence, the consensus seems universal: it is a horror… except for the perpetrator. This “self-tolerance”, far from being a simple denial, is based on concrete biological and psychological bases.
The result of banal biological mechanics
A fart is nothing more than the expulsion of intestinal gas, a natural byproduct of digestion. Made up of nitrogen, hydrogen, carbon dioxide and methane, it is technically odorless…mostly.
According to Dr. Pauline Guillouche, hepatologist, our gases are indeed commonplace. “It is the sulfur compounds which are responsible for the odors. The rest of our gases are odorless” she explains. These compounds, like hydrogen sulfide, arise from the breakdown of proteins and certain foods (cabbage, red meat, onions) by the bacteria in our large intestine.
Why do our own gases seem “sweeter” to us?
If the smell of others repulses us, ours is familiar to us. Science offers several explanations for this preference:
- The bacterial habit. We live in symbiosis with our own intestinal flora. The brain recognizes the chemical signature of our own bacteria and associates it with our biological “self,” making it less threatening;
- The survival instinct. Evolutionarily, a strong odor coming from others is a signal of danger or potential illness (such as the presence of the bacteria Streptococcus pyogenes). Conversely, our own smell is perceived as a sign of good internal functioning;
- Self-recognition. A 1976 study showed that even if we do not always recognize our smell blindly, we almost systematically classify our sample as the least unpleasant of the lot.
Hydrogen sulfide: an unexpected ally for the brain?
As surprising as it may seem, this gas with the smell of rotten eggs that we produce could have therapeutic virtues. Researchers at Johns Hopkins Medicine have found that at very low doses, hydrogen sulfide protects brain cells against cognitive decline.
In tests on mice, the controlled introduction of this gas improved cognitive and motor functions by 50%. It would prevent the formation of toxic clusters linked to Alzheimer’s disease. Be careful though: “Hydrogen sulfide is toxic in high doses, and its inhalation is not therapeutic” specifies the study.
A question of healthy living and acceptance
The smell of flatulence can vary depending on individual health and stress. A 2021 study even linked a high presence of gas symptoms to higher levels of anxiety. But on a strictly medical level, Dr Guillouche wants to be reassuring. “The smell, however strong it may be, is not a sign of illness, but simply a reflection of what we eat.”
Accepting the smell of your own farts would therefore be an ultimate form of self-acceptance, a silent (or loud) rebellion against the social norms that stigmatize our most basic bodily functions.