Coffee and its Impact on the Human Body
I. Introduction: The “Compelling Urge to Defecate”
- The Phenomenon: Coffee often induces a strong urge to defecate shortly after consumption.
- Initial Questions:
- Why does this happen so quickly?
- Is it a digestive process?
II. Coffee and Digestion (Stomach)
- Common Belief: Coffee as a “digestif” after meals.
- Research Findings:
- Coffee does increase gastric juices in the stomach.
- This aids digestion.
- Crucially: It does not speed up gastric emptying (moving food from the stomach to the next stage of the gastrointestinal tract).
- Caffeine’s Role: This effect is observed with both caffeinated and decaffeinated coffee, indicating caffeine is not the primary driver for increased gastric juices.
- Conclusion for Stomach Phase: While coffee impacts the stomach, it doesn’t explain the “compelling urge to defecate” as it doesn’t accelerate the movement of contents.
III. Coffee and the Microbiome (Gut)
- Impact on Gut Bacteria: Coffee consumption influences gut bacteria composition.
- Specific Bacteria: A recent study identified Laucinobacter acycroliticus as a bacteria uniquely present in coffee drinkers. This is the first time a bacterial population has been linked to a single foodstuff.
- Health Outcomes (Fringe/Cutting-Edge Science):
- Connecting coffee and gut bacteria to health outcomes is still an emerging field.
- Associations: Coffee consumption is linked to positive health outcomes, such as reduced mortality.
- Mechanism: Coffee may provide the “right kind of food” for Laucinobacter, which in turn produce butyrate. Butyrate is associated with positive health outcomes.
- Decaf’s Role: Decaffeinated coffee also shows positive outcomes, likely due to its phenolic compounds (not polyphenols, as clarified by Beanie). These compounds are what the bacteria “crave.”
- Conclusion for Microbiome Phase: Coffee impacts gut health and may contribute to overall well-being through its interaction with bacteria and production of butyrate. However, this process is too slow to explain the immediate “compelling urge.”
IV. Coffee and the Nervous System (The Answer)
- Initial Hypothesis: Could it be hormone-based? (Rejected in the context of the study).
- Key Study (Rats):
- Methodology:
- Took a piece of gut tissue from a live rat.
- Kept tissue alive in a mineral/electrolyte bath.
- Added coffee to the bath.
- Observed gut contractions.
- Identifying the Mechanism:
- Added different nerve inhibitors/blockers to the solution.
- Atropine was found to stop the coffee’s effect.
- Atropine inhibits muscarinic receptors.
- Methodology:
- Muscarinic Receptors:
- Part of the enteric nervous system (the “brain of the gut”).
- Present throughout the gut and even in the mouth.
- Mechanism: From the moment coffee is sipped, the muscarinic system sends a signal to the gut, causing it to contract, leading to the “compelling urge to defecate.”
- Synergy with Nicotine: Nicotine also triggers muscarinic receptors, explaining the powerful synergistic effect experienced by those who consume both coffee and nicotine.
- Conclusion: The “compelling urge to defecate” is a nervous system response, specifically triggered by coffee activating muscarinic receptors in the gut.
V. Unanswered Questions & Future Research
- Specific Compound: What specific compound(s) in coffee trigger the muscarinic receptors?
- It’s not caffeine (decaf has the same effect).
- Personal experience suggests darker roasts might be more compelling than lighter roasts.
- Call to Science: Now that the mechanism is understood, identifying the specific compound should be an easier question to answer.