Does coffee dehydrate you? Probably not at moderate amounts, and swallowed gum doesn't stay in your stomach for seven years either. Most gut myths you grew up with don't hold up. These old wives' tales usually start with a small truth and stretch it into a rule, so here's what the evidence actually says. For the modern ones, detox teas and all, see our gut health myths vs facts guide.
Swallowed gum does not stay in your stomach for seven years, moderate coffee does not appear to dehydrate habitual drinkers, and spicy food is not thought to cause stomach ulcers. Most persistent gut myths start with a small truth and stretch it into a rule. Noticing your own patterns over time can tell you more than folklore.
What happens if you swallow gum?
Usually nothing much. Gum base isn't digested, but it doesn't stay in your stomach for seven years either. It usually moves through your digestive system and leaves with everything else, on roughly the timeline in our guide to how long food takes to digest. Blockages have been reported only rarely, mostly in children who swallowed large amounts frequently [1].
Does fruit rot in your stomach after a meal?
No. This idea comes from food combining diets, but your digestive system is built for mixed meals. Your stomach churns everything together with acid and enzymes, then releases it gradually into the small intestine, where most nutrients are absorbed; our guide to the small and large intestine explains the next stage. Fruit doesn't sit and rot while it waits its turn. As supporting context, one randomised trial found a food combining diet led to no more weight loss than a balanced diet with the same calories [2].
Does coffee dehydrate you?
Probably not at moderate amounts. So is coffee dehydrating? Caffeine has a mild diuretic effect, but in a small study of habitual male coffee drinkers having moderate amounts, researchers found no meaningful difference in hydration markers compared with the same volume of water [3]. That may not apply identically to everyone or every intake level. Coffee does appear to stimulate the bowel in some people [4], as our pieces on coffee and gut health and the gastrocolic reflex explain. Our urine colour chart is a rough everyday guide to hydration, though colour can be affected by other things too.
Can stress or spicy food cause stomach ulcers?
For decades this was accepted wisdom. Then Robin Warren and Barry Marshall described the bacterium now called Helicobacter pylori in the stomach lining [5], work that later earned a Nobel Prize [8]. The NHS now lists H. pylori infection and long-term use of anti-inflammatory painkillers such as ibuprofen as the most common causes [6]. Ordinary day-to-day stress is not considered a main cause of most stomach ulcers, although severe physical stress during serious illness is a different and more complex situation. Stress can still affect how your gut feels, as our guides to stress and gut health and anxiety and stomach pain cover. Spicy food may irritate an existing ulcer, but it isn't thought to cause one. Ongoing stomach pain is always worth discussing with your GP.
Is flat Coke good for an upset stomach?
Flat Coke or cola is a classic family remedy, but it's mostly sugar and water, with little of the salts your body loses through diarrhoea or vomiting. For managing a stomach bug, the NHS advises plenty of fluids, such as water, in small sips if you feel sick, and suggests asking a pharmacist about oral rehydration sachets if you're at risk of dehydration [7]. Our guide to hydration and digestion explains why fluid matters.
| Myth | What the evidence suggests | Verdict |
|---|---|---|
| Gum stays for seven years | It usually passes through; blockages are rare [1] | Myth |
| Fruit rots after a meal | The stomach and small intestine handle mixed meals | Myth |
| Coffee dehydrates you | No meaningful dehydration at moderate intake in one small study [3] | Mostly myth |
| Spicy food and stress cause ulcers | H. pylori and anti-inflammatory painkillers are the main causes [6] | Myth |
| Flat Coke settles an upset stomach | Water and, if needed, oral rehydration sachets are advised [7] | Myth |
Frequently asked questions
Why do gut myths keep coming back?
They're simple, they come from people we trust, and they usually hold a sliver of truth. Gum really isn't digested. Caffeine really is a mild diuretic. Spicy food really can sting. The trouble starts when a small truth is stretched into a rule for everyone. Our piece on your gut feeling looks at another phrase with more science behind it than you'd think.
Is peppermint tea good for an upset stomach?
Some people find peppermint helpful for bloating, and there's some research behind it, although evidence varies by product and person. Our article on peppermint tea and bloating looks at what the studies actually show, and how to get rid of bloating and gas covers other options worth trying.
How can I tell what works for my own gut?
Digestion is personal, so what one person swears by may do nothing for the next. Noticing your own routine over a few weeks tends to be more useful than any rule handed down. Our 30-day gut health tracking challenge shows a simple way to start, and the Bristol Stool Chart guide gives you a shared language.
The best antidote to folklore is noticing your own patterns. Next time a family remedy comes up, check it against the evidence, then watch how your own gut responds over a week or two rather than a single day. Gutsi is a gut health tracker designed to help you spot patterns in your digestive routine over time, rather than relying on memory alone, or on what your nan swore by.
References
- Milov DE, Andres JM, Erhart NA, Bailey DJ. Chewing gum bezoars of the gastrointestinal tract. Pediatrics. 1998;102(2):e22. https://doi.org/10.1542/peds.102.2.e22
- Golay A, et al. Similar weight loss with low-energy food combining or balanced diets. International Journal of Obesity. 2000;24(4):492-496.
- Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS ONE. 2014;9(1):e84154. https://doi.org/10.1371/journal.pone.0084154 (Small study of habitual male coffee drinkers.)
- Rao SS, Welcher K, Zimmerman B, Stumbo P. Is coffee a colonic stimulant? European Journal of Gastroenterology & Hepatology. 1998;10(2):113-118. (Small study.)
- Warren JR, Marshall B. Unidentified curved bacilli on gastric epithelium in active chronic gastritis. The Lancet. 1983;321(8336):1273-1275.
- NHS. Stomach ulcer. nhs.uk
- NHS. Diarrhoea and vomiting. nhs.uk
- NobelPrize.org. The Nobel Prize in Physiology or Medicine 2005. nobelprize.org
Gutsi provides lifestyle and wellness insights only. It is not intended to diagnose, treat, cure or prevent any disease, and should not be used as a substitute for professional medical advice.
