Is caffeine responsible for our routine bathroom breaks after coffee?

Most of us know what it's like - you made your first cup of coffee in the morning and you sit down at your desk ready for your super productive day ahead. Two sips in and now you're just about ready for your first bathroom break, courtesy of the aromatic cup of energy in front of you. You'll probably end up taking a couple more breaks after this one, too. 

But why does this happen? Could it be the caffeine found in your daily drink? Or is it something else...

A 1998 study found that caffeine contributes to the laxative effect of coffee but does not explain it fully. In the study, 12 volunteers were given coffee, decaffeinated coffee, water, and a 1000-calorie meal. Their colonic responses to what they were given were measured by detecting pressure changes using a manometer. The results of this study showed that the 1000-calorie meal stimulated an equivalent amount of activity as the regular coffee did. Decaffeinated coffee lessened the amount of colonic activity but did not eliminate it and water had the lowest activity. It was also discovered in another study that caffeine induces stronger anal sphincter contractions and therefore an increased desire to defecate, as opposed to water.

This suggests that the gastrointestinal effects of coffee cannot be explained only by caffeine and that alternative reasons should be explored.

So, we know that caffeine in our coffee is not the sole reason for our bathroom breaks. If this is the case, what is also contributing to them? 

There are 2 possible reasons that we'll discuss in this article: 

1. The Hormone Gastrin 

2. The Gastrocolic Reflex. 

1. The Hormone Gastrin

Here's the deal with gastrin. Gastrin is a peptide hormone secreted by the G-cells found in our stomach linings and upper small intestine. It aids in gastric motility, enhances the growth of the gastric mucosa, and stimulates the release of gastric acid (HCl) which promotes digestion. 

Both regular and decaffeinated coffee stimulate gastrin. When gastrin is released, the stomach releases HCl and digestive enzymes which causes the stomach to contract, relaxing the valve between the small and large intestines and the sphincter found between the stomach and small intestine. Effectively, gastrin secretion stimulates digestion. When digestion begins, the desire to defecate also increases. 

This is how gastrin may aid caffeine in causing our bathroom breaks after coffee.

If you're more of a visual learner, figure 1 below sums it up:

Figure 1: How Gastrin Stimulates Defecation

2. The Gastrocolic Reflex

If this is your first time hearing this term - you are not alone. 

The Gastrocolic Reflex is a physiological reflex responsible for peristalsis in the lower gastrointestinal tract after food/drink is ingested. It increases colon motility to make room for more after the stomach stretches with its contents. The reflex is controlled by many factors, including gastrin and so when you consume coffee, gastrin is secreted, which induces the gastrocolic reflex and increases colonic contractions, leading to defecation. Now here's the interesting part... this reflex is especially active in the morning. 

The gastrocolic reflex is significantly reduced in the evenings and at night but is increased right after waking up. This link between bowel activity and the circadian rhythm would explain why your morning coffee usually comes with a ticket to the bathroom but your evening/night coffees don't. 

And there you have it. This is how the gastrocolic reflex may be working alongside caffeine in causing our routine bathroom breaks after coffee (Figure 2). 

Figure 2: The Gastrocolic Reflex 

As with everything else in life, there are 🌟exceptions🌟

There are, of course, lucky ones among us who have absolutely no issues when they have a cup of coffee whereas others only need to smell the coffee to know what they're in for.

For those of us that aren't as lucky, now we know what else may be causing our bathroom breaks when we have coffee!

Are you lucky? 🤔

Hey there! Hope you learned something new from this 😊

If you've got any questions - leave me a comment & I'll get back to you as soon as I can!

Until next time, stay safe & ambitious - TCB 💛

REFERENCES

Malone, Jordan C, and Aravind Thavamani. 2022. “Physiology, Gastrocolic Reflex.” Nih.gov. StatPearls Publishing. May 8, 2022. https://www.ncbi.nlm.nih.gov/books/NBK549888/‌. 

McGill University. 2020. “Why Does Coffee Make You Poop?” Office for Science and Society. June 29, 2020. https://www.mcgill.ca/oss/article/health-nutrition/why-does-coffee-make-you-poop.

Prosapio, Jordon G, Parvathy Sankar, and Ishwarlal Jialal. 2022. “Physiology, Gastrin.” Nih.gov. StatPearls Publishing. March 9, 2022. https://www.ncbi.nlm.nih.gov/books/NBK534822/‌‌.

You and Your Hormones. 2022. “Gastrin | You and Your Hormones from the Society for Endocrinology.” Yourhormones.info. 2022. https://www.yourhormones.info/hormones/gastrin/.