Why does coffee open your bowels?

Some of you may have noticed the urge to visit the toilet after having your morning cup of coffee – but why is this? Well, several factors contribute to this phenomenon, including the influence coffee has on your digestive hormones and colon function, and the timing of your coffee consumption. For many individuals, coffee induces bowel movements, and this effect occurs even when drinking decaffeinated coffee.

In fact, a recent study demonstrated how coffee can assist postoperative patients in preventing constipation and having more regular bowel movements. Not everyone feels this way after drinking coffee though – some people may be more sensitive than others and find this 'assistance' is less than helpful.

What your coffee is doing to your body

Here are some of the reasons why your morning cuppa can lead to bowel movement.

1. The gastrointestinal reflex

The gastrointestinal reflex is triggered when your stomach stretches as you eat or drink, causing increased mobility in the large intestine. Essentially, your body tries to push old food out of your intestines to make way for new food. This reflex is particularly active in the morning, so having coffee or another hot beverage after waking up can help stimulate this reflex and open your bowels.

2. The digestive hormone

Both caffeinated and decaffeinated coffee can stimulate the production of the hormone gastrin, which helps the intestines move. Gastrin also promotes the gastrocolic reflex.

3. The temperature of your drink

Studies show that even drinking hot water can stimulate bowel movement. Your digestive tract is more sensitive and prone to activity early in the day. Consuming a hot beverage directly affects your stomach and bowel reflex, facilitating intestinal movement.

However, temperature doesn't account for all coffee effects. People who feel the need to use the restroom after coffee consumption don't always experience the same urge after consuming other hot drinks like tea. One study that looked at the effects of warm water on bowel movements, found that warm water ingested post-surgery notably reduced the time it took for the first passing of gas and had a positive impact on intestinal movements. A recent paper has shown that 29% of patients with irritable bowel syndrome reported that coffee worsened their symptoms. Hence, for individuals with predominant diarrhoea in conditions like IBS or sensitive bowels, it may be wise to limit coffee intake if they find it causes them to visit the restroom too frequently.

Nutritional strategies that can help you when constipated

The key thing you can do is to increase your diet's fibre content – fibre is the component of plant-based foods that the intestinal lining cannot absorb, thus it adds volume to faeces. It aids in relieving constipation by increasing the size of each bowel movement and functioning as a sponge, absorbing moisture into the stool, resulting in a softer consistency that facilitates smoother passage through the digestive system.

How can I have more fibre in my diet?

• Choose a higher-fibre breakfast cereal such as porridge oats, shredded wholegrain cereals or whole-wheat biscuits.
• Add more pulses, such as lentils, beans or chickpeas to stews and salads.
• Include vegetables with every meal, and keep the skin on vegetables, if possible.
• Have more fruit daily (this can be fresh, tinned or dried fruit).
• Read food labels. High-fibre foods contain more than 6g of fibre per 100g. Foods that contain less than 3g of fibre per 100g are considered low in fibre.

A diet high in fibre can help to maintain a healthy weight and lower the risk of heart disease, diabetes and some cancers. However, it is important to incorporate them gradually into your diet, as a sudden alteration or boost can lead to stomach discomfort.

Diversify the kinds of fibre (e.g. soluble fibre) you consume, as insoluble fibre can induce bloating and discomfort in certain individuals.

Before making any changes to your diet, particularly regarding supplements and your gut and digestive health, it is recommended you consult a medical professional. A nutrition expert, such as a dietitian, can help you understand your individual needs and how you can safely adapt your diet to provide you with the nutrients your body requires.

References

• ACQUAVIVA, F., et al., Effect of regular and decaffeinated coffee on serum gastrin levels. Journal of Clinical Gastroenterology, 8(2), pp. 150-153.
• BROWN, S.R., CANN, P.A, and READ, N.W., 1990. Effect of coffee on distal colon function. British Medicine Journal, 31(4), pp. 450-453.
• NEFISE, C., BULUT, H., and KONAN, A., The effect of warm water intake on bowel movements in the early postoperative stage of patients having undergone laparoscopic cholecystectomy: a randomized controlled trial. Gastroenterol Nurs, 39(5), pp. 340-347.
• NUNTASIRI, E., et al., 2018. Effect of postoperative coffee consumption on gastrointestinal function after abdominal surgery: A systematic review and meta-analysis of randomized controlled trials. Scientific Reports, 8.Gill, S.K., Rossi, M.,
• BAJKA, B. et al. Dietary fibre in gastrointestinal health and disease. Nat Rev Gastroenterol Hepatol 18, 101–116 (2021). https://doi.org/10.1038/s41575-020-00375-4.