Feeling a burning sensation in the chest or throat is usually associated with acid reflux. The acid irritates the food pipe (oesophagus), causing inflammation. If it’s persistent, it’s known as gastroesophageal reflux disease (GERD/GORD). The same symptoms can occur without acid reflux. This is known as functional heartburn.

Functional heartburn is largely unknown and underappreciated. However, it is the most common cause in patients who don’t respond to proton pump inhibitors (PPIs), the first-line treatment for GERD. As such, functional heartburn often goes undiagnosed.

What Is Functional Heartburn

Functional heartburn is a burning sensation in the chest that isn’t caused by acid reflux or any structural issues in the oesophagus. Because the heartburn isn’t caused by acid, it doesn’t:

• respond to antacids, proton pump inhibitors, or H2 blockers

• have a positive result from an endoscopy, 24-hour pH monitoring, or oesophageal manometry

• have any visible signs of oesophageal damage, inflammation, or hiatal hernia

The condition is, therefore, classified as a functional gastrointestinal (GI) disorder, where symptoms are real but not caused by visible abnormalities.

Symptoms of Functional Heartburn

Symptoms may overlap with GERD but tend to persist even when acid levels are normal or well-controlled. Common signs include:

• A burning sensation in the chest or upper abdomen

• Discomfort or pain after eating

• Throat irritation or a sensation of acid rising

• Chest tightness or pressure not linked to exertion

• Heartburn that does not improve with proton pump inhibitors (PPIs)

• Occasional nausea or mild bloating

• Anxiety or sleep disturbance related to persistent symptoms

Unlike GERD, functional heartburn does not cause tissue injury, and tests such as an endoscopy or pH monitoring typically appear normal.

Causes of Functional Heartburn

The exact cause of functional heartburn isn’t fully understood. It’s believed that several factors are involved, including:

Oesophageal Hypersensitivity

The nerve lining the oesophagus can become overly sensitive. If this is the case, then even minor or normal events like swallowing or slight acid exposure may lead to discomfort.

Stress and Emotional Distress

Stress and emotional distress increase our awareness of bodily sensations. The more stressed you are, the more likely you are to experience functional heartburn.

Heightened Pain Perception

Pain perception isn’t controlled by the tissues themselves. If the brain misinterprets signals from the digestive tract, it can lead to non-harmful stimuli feeling painful or uncomfortable, even if nothing is going on.

Gut-Brain Dysfunction

Your gut contains the second-highest density of nerves in the human body. It’s often called the “second brain.” If the signals it sends back to the brain become exaggerated, it can be interpreted as pain or discomfort.

Diagnosis of Functional Heartburn

Patients with functional heartburn are almost always diagnosed with gastroesophageal reflux disease (GERD) initially. It’s only when they don’t respond to treatment that other conditions are considered.

Often, patients who experience persistent heartburn or don’t respond to PPIs are sent for the following tests:

Upper Endoscopy

An endoscopy involves guiding a camera down a patient’s oesophagus to visualise the area. It’s normally performed due to concerning symptoms such as difficulty swallowing, vomiting, unexplained weight loss, or signs of gastrointestinal bleeding.

If necessary, a biopsy can be taken and sent for testing.

Oesophageal Manometry

If an endoscopy is inconclusive, another potential cause is an oesophageal motility disorder. Manometry measures the contraction of the oesophageal muscles and can therefore identify any problems with these muscles, including relaxation of the LES.

Oesophageal pH Testing

Oesophageal pH testing is the gold standard test for GERD. A pH probe is guided down your oesophagus and left there for 24 hours. It measures changes in pH, detecting if reflux occurs, and recording these measurements on a monitor you wear with it.

Diagnosis or Elimination

If all these tests are negative but symptoms persist despite treatment, then a diagnosis of functional heartburn can be considered.

Treating Functional Heartburn

Functional heartburn cannot be treated with conventional heartburn medications. Antacids or PPIs don’t work. Most dietary changes do not significantly improve functional heartburn either.

Instead, the focus is on downregulating the brain’s response to the pain signals.

Neuromodulators such as amitriptyline, duloxetine, or citalopram can help soothe oesophageal nerve sensitivity. Some of these medications are anti-depressants; however, they also work as pain modulators at low doses.

Techniques like cognitive behavioural therapy (CBT), medical hypnosis, and mindfulness can teach patients to adjust their response to symptoms. By managing discomfort and stress, over time, the symptoms can lessen.

Some dietary changes can also make a difference. Spicy, acidic, or fatty foods can cause acid reflux. Given the oversensitivity to pain signals, avoiding acid reflux is crucial, as this can exacerbate the condition.

Still experiencing heartburn even after taking PPIs? It could be functional heartburn, not acid reflux.

Speak to our experts at The Functional Gut Clinic to arrange specialist testing and diagnosis.