Heartburn is best described as a painful, burning sensation that occurs in the lower chest area.

It is a symptom of acid reflux, a condition where stomach acid escapes into the esophagus, the tube that delivers food and beverages to your stomach.

Normally, stomach acid cannot escape into the esophagus because of a barrier called the lower esophageal sphincter. This is a ring-like muscle that naturally stays closed, and normally only opens when you swallow or belch.

However, in people with acid reflux, this muscle is often weakened. This is one reason why people with acid reflux experience heartburn.

Diet plays an important role in heartburn. Many foods can relax the lower esophageal sphincter, which allows food to escape into the esophagus and cause heartburn.

Here are 5 foods that can cause heartburn:

1. Citrus fruits

As surprising as it sounds, oranges, grapefruits, and orange juice are classic heartburn foods.

According to research, the aforementioned fruits are very acidic and more likely to cause heartburn as result of their nature when consumed on an empty stomach.

2. High-fat foods

However, studies have shown that there are two ways high-fat foods can trigger heartburn.

First, they may relax the lower esophageal sphincter, the muscle that acts as a barrier between the esophagus and the stomach. When this muscle relaxes, stomach acid can escape from the stomach into the esophagus and cause heartburn.

Second, high-fat foods stimulate the release of the hormone cholecystokinin (CCK). This hormone may also relax the lower esophageal sphincter and cause acid reflux.

3. Spicy food

Recent studies have shown that spicy foods often contain a compound called capsaicin, which may slow the rate of digestion. And when this happens, foods are likely to sit in the stomach longer than usual, which is a risk factor for heartburn.

For example, one study showed that consuming chili that contained chili powder slowed the rate of digestion. In addition, spicy foods may irritate an already inflamed esophagus, and this can worsen heartburn symptoms.

Thus, it is advisable to reduce your intake of spicy foods if you’re prone to heartburn.

4. Onion

Although the health benefits of onion are priceless, studies have shown that it is a common trigger for heartburn, especially when it is consumed raw.

And this is because it relaxes the lower esophageal sphincter, which may cause acid reflux and symptoms of heartburn.

Recent studies have also shown that onions are a rich source of fermentable fiber, which may cause belching; and belching can aggravate acid reflux symptoms.

5. Milk

Although milk is commonly consumed to treat heartburn, studies have shown that drinking whole milk may actually cause symptoms, instead of relief.

As a matter of fact, a recent research suggests that whole milk may increase stomach acid production, which is a risk factor for heartburn.