Coffee and Shit

The Aroma of Coffee and Nature's Call: Not a Placebo but a Physiological Reality

For many, the morning aroma of coffee is a promise of awakening and comfort. For others, this simple smell seems to almost instantly trigger an urgent need to move their bowels. Often dismissed as a coincidence or a placebo effect, this reaction is nevertheless rooted in very real physiological mechanisms. Far from being an "absence" of an active substance, the smell of coffee is a powerful chemical message that speaks directly to our body.

To understand this phenomenon, we must first dismiss the idea of a placebo. A placebo effect occurs when a person experiences a change following the intake of an inert substance or procedure, solely through the power of belief or expectation. However, the smell of coffee is not intangible. It is made up of a complex cocktail of hundreds of volatile organic compounds. These very real chemical molecules are the true messengers that initiate the cascade of reactions.

Our body is a sophisticated anticipation machine. Even before the first sip of coffee (or any other food) reaches our stomach, the smell is enough to set the digestive system in motion. Olfactory receptors located in our nose capture these odorous molecules and transmit the information to the brain. In response, the brain commands the release of hormones and neurotransmitters that prepare the ground: salivation increases, the stomach begins to secrete gastric juices, and, crucially for our topic, the motility of the gastrointestinal tract, including that of the colon, can accelerate. This digestive "start-up," triggered by olfaction, can therefore be enough to stimulate intestinal peristalsis – the muscular contractions that move stool along.

Therefore, the urge to have a bowel movement triggered by the smell of coffee is neither a whim nor a trick of the mind. It is the result of a complex interaction between concrete chemical signals and the sophisticated responses of our organism; it is an elegant demonstration of how our senses and our physiology are intimately connected, orchestrating responses from the very first chemical signals.