Noah Fagan says he “used to go through antacids like sweets. I had a big list of foods I couldn’t eat. I’d take at least three antacids on average – going up to six on a bad day. This went on for at least seven years.”

If you have reached for a chalky tablet after a blow-out meal, you are not alone. So common is antacid use for heartburn and indigestion that the World Health Organization says more than $10bn (£8.2bn) worldwide is spent on them every year. In the UK, more than 40% of us use them – 2.8 million people reach for the market leader, Rennie, alone.

Indigestion is often caused by excess stomach acid and results in discomfort, pain, bloating, nausea or wind. With acid reflux, acid travels up the oesophagus to the throat, leaving an unpleasant, sour taste. Alexander Ford, a professor of gastroenterology at the University of Leeds, says: “The two main groups of antacids are those that contain an alkali which ‘neutralises’ acid, like Rennies; and those that are alginates, like Gaviscon, which form a ‘raft’ on top of stomach contents, preventing reflux up into the oesophagus.”

Antacids are perfectly safe when taken correctly. The problem is that many of us don’t. Who has read the small print and knows that you shouldn’t take aspirin or ibuprofen at the same time as Gaviscon, because it can affect the way the painkillers are absorbed by your body? That’s important to know if you take daily aspirin to lower the risk of stroke. Conversely, did you know that some antacids, such as Alka Seltzer, contain aspirin? That could be important, too – in 2016, the US Food and Drug Administration (FDA) issued a warning that excessive aspirin use can cause stomach bleeding.

Though antacids may alleviate symptoms in minutes, over-reliance on them may not only mask more serious issues but could even create them. Fagan, a 42-year-old architect from Bristol, says: “It was only while my wife was pregnant and suffering acid reflux herself that it got mentioned to our GP. It wasn’t a food issue at all, but a medical problem.”

Fagan was diagnosed with overactive acid production and started taking proton-pump inhibitors (PPIs), which act to reduce stomach acid production, rather than simply neutralising it. Now, Fagan rarely needs to take them. However, the duration of treatment can vary hugely, and this is important as long-term PPI use is linked to side-effects including pneumonia, hypocalcaemia and Clostridium difficile infections (leading to severe diarrhoea). One study even made a link between PPI use and early death. Some PPIs are available over the counter, which has led to concern that – like antacids – they will be overused and under-monitored. The FDA has issued warnings and the NHS notes that prolonged use should be avoided.

In fact, according to US research, the majority of people with recurring heartburn don’t seek medical advice at all, instead self-treating the symptoms for years. This may also have had a significant effect in skewing data – the researchers note that women are more likely to seek medical attention than men, “resulting in the false impression that nonerosive reflux disease and functional heartburn are primarily female disorders”.

For everyone, even innocuous-looking over-the-counter remedies should be used carefully. “In terms of using them ‘blind’, they are treating a symptom, not a disease,” says Ford. “If someone has had an endoscopy and this is normal, then it is reasonable to use them. In most young people with indigestion, there will not be a serious underlying cause, so they are probably OK. But in older people – above 50 or 55 years – the worry would be that people are using them to treat dyspepsia where the cause is unknown, as they might be masking the symptoms of a peptic ulcer or a stomach cancer. These people really should consult their GP.”

Bayer, which makes Rennie, says: “Bayer encourages people taking antacids to read the information provided with the product. Antacids will only manage the symptoms rather than curing a problem. As with all antacids available without a prescription, if symptoms persist for longer than 14 days in a row, then it is advisable to see a healthcare professional to check that there is no underlying cause.” This information is clearly stated on the packet, too – if we only read it.

For all indigestion sufferers, the message is consistent: if symptoms persist, see a doctor to rule out anything serious. If all is well, then you can try to reduce your reliance on antacids and alleviate symptoms by other means. Specific foods may be triggers, but generally it’s a good idea to avoid very spicy, greasy or fatty foods. Eating smaller but more frequent meals can help, as can losing weight if you are overweight. Try not to eat just before bed; allow for an hour or so before you lie down. You can also try raising your bed at one end, so that when you lie down, your head and chest are raised – enlisting gravity’s help in reducing the stomach acid travelling up to your oesophagus. And if you do use antacids, read the label.