Explainer: what is gastric reflux?

Gastric reflux is brought on by spicy and acidic food and drink, alcohol and overeating. Image from shutterstock.com

If you’re prone to gastric reflux, you’ll probably be watching closely what you eat and drink during the pre-Christmas party season. You’re certainly not alone; modern, heavy eating habits and a rise in obesity mean the condition is more common than ever, affecting nearly three in every ten people worldwide.

Gastric reflux, commonly referred to as heartburn or indigestion, leaves sufferers with a painful burning sensation in the stomach or behind the breastbone and is often coupled with regurgitation.

There are various types of gastro-oesophageal disease, as reflux is clinically known, which vary in the degree of damage to the inner lining of the oesophagus and the level of pain experienced.

Causes

First, some basics. The oesophagus is the tube which connects the throat to the stomach; between the stomach and oesophagus is a valve or “sphincter” which prevents the backflow of stomach contents – the acid that aids digestion.

When the sphincter is weak, stomach acid is forced upwards. Image from shutterstock.com

When the sphincter is weak or there is increased pressure within the stomach, acid can flow backwards into the oesophagus. This is often brought on by spicy or acidic food or drink, alcohol and overeating.

The stomach acid irritates the oesophagus, which is lined with very sensitive tissue, densely packed with sensory nerve endings.

In healthy people, these sensory nerves send signals to the brain alerting us to potential harm, provoking automatic reflexes such as coughing and contractions of the oesophagus. This will clear the acid or increase saliva production to neutralise the acid and protect the oesophagus.

There are also specialised sensory nerves that relay information via spinal cord pathways to parts of the brain that control our conscious awareness of pain. Activation of these specialised nerves triggers a pain response and, in the case of gastric reflux, drives us to reach for the Mylanta.

Complications

In people with a weak sphincter or an underlying illness such as a hernia or increased stomach acidity, prolonged and repetitive acid backflow may damage the oesphageal lumen lining.

As a result, the sensory nerves also become damaged, undergoing changes that make them abnormally sensitive and magnifying the pain signals sent to the brain. This hypersensitivity is usually temporary, but in some cases it can be permanent.

To reduce your risk of an episode, avoid trigger foods, especially before bed. Image from shutterstock.com

If permanent, the sensitivity can trigger changes within the spinal cord “pain” pathways, making them abnormally responsive to the input they receive. If these spinal cord pathways are altered, the gastric reflux pain may become chronic and the patient may feel pain in response to normally painless stimuli or even in the absence of acid reflux.

The transfer of sensitivity from sensory nerves to spinal cord pathways is also thought to underlie some of the more confusing long-term pain symptoms of gastric reflux such as non-cardiac chest pain.

Treatment

Over-the-counter antacids provide immediate, short-term relief. They work by neutralising stomach acidity or forming a protective layer on top of the stomach contents – or on the inner lining of the oesophagus.

The prescribed therapies for chronic gastric reflux sufferers are primarily aimed at reducing stomach acidity in order to prevent ongoing damage to the oesophageal lining. This allows damaged tissue to heal, and ensures that nerve endings don’t become sensitised. Proton pump inhibitors, a class of drugs that suppress acid, often alleviate symptoms within eight weeks.

But some people do not respond well to such therapy or the effects wear off over time. This may occur if the damage to the sensory nerves has been severe enough to cause remodelling of the spinal cord pathways.

Antacids provide immediate, short-term relief by naturalising stomach acidity. dianaschnuth

As such, it’s important to identify and understand the workings of these specialised sensory nerves and the spinal cord pathways that relay pain information. This is what my colleagues and I sought to do in a recently published study examining the neurological activity of mice with acute acid reflux. We were able to identify the sensory neurons activated by oesophageal acid, and the spinal cord “pain” pathways they relay information into.

Such information will allow us to identify changes within this pathway due to chronic acid exposure. This is key to our understanding of what causes gastric reflux pain, and may explain why current therapies are not effective in some people. It will also allow us to improve therapies, with alternate treatments being developed that are aimed at correcting the sensitivity of damaged sensory nerves.

If you’re concerned about gastric reflux, talk to your general practitioner about possible treatments. In the meantime, there are some steps you can take to reduce reduce your risk of an episode, such as eating smaller meals, watching your weight and avoiding trigger foods, especially before bed.