Can onions cause heartburn?

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Onion is a widely used, healthy vegetable. However, many people find that onions exacerbate their heartburn, therefore onions are not recommended for people with acid reflux or gastroesophageal reflux disease (GERD).

Health benefits of onions

Onion (Allium cepa L.,) is a vegetable of the Allium genus. Its origin is uncertain, though its use dates to 5000 BC in China.

Onions were also used in ancient Egypt for burial purposes, and traces of onions were found in the eyeball sockets of Ramesses.


It has been used both as food and medicine for many centuries and it comes in different colors: red or purple, brown or yellow, and white.

Onions have many health benefits, including:

  • contain antioxidants
  • beneficial for the heart
  • good for bone density
  • have antibacterial effects

However, despite the many health benefits, onions might cause symptoms like heartburn in sensitive people.

Are onions acidic?

The pH ranges for onions are as follows:

  • 5.3 – 5.8 for red onions
  • 5.4 – 5.8 for yellow onion
  • 5.4 – 5.6 for white onion

Onion is therefore classified as a slightly acidic food because its pH is less than 7.

A pH of around 5.5 is not considered to be an issue in terms of acid reflux. Gastric acids are far more acidic with a pH around of 1-2.

However, as discussed below, onion can still cause symptoms for heartburn sufferers, but not because of its slightly acidic nature.

Can onions give you heartburn?

Yes, onions are common heartburn triggers (refluxogenic), especially raw onions. Several research studies have reported heartburn symptoms experienced by sensitive people who ate alliums – like onions – or foods containing onions.

A study examining 32 people found:

Ingestion of onions did not increase any of the reflux variables measured in normals. However, onions significantly increased all measures in heartburn subjects, compared with the no-onion condition, and compared with normals under the onion condition. Onions can be a potent and long-lasting refluxogenic agent in heartburn patients.


So those who are prone to having heartburn might want to stay away from onions, as it could exacerbate reflux symptoms.

However, as mentioned above, the acidity of onions is unlikely to be the trigger. There must be some other ingredients in onions that worsen the symptoms of heartburn sufferers.

Why do onions cause acid reflux?

Onions can increase the risk of an acid reflux episode in several ways:

A relaxed LES

Some experts speculate that onions might relax the LES (lower esophageal sphincter).

The LES is a muscle between the food pipe and the stomach. When this muscle is tight, it prevents stomach acids from entering the esophagus and causing heartburn.

A relaxed LES muscle is a risk factor for acid reflux.

Onions might cause gas

Onion contains high amounts of fructans, a carbohydrate (an oligosaccharide to be more specific) that belongs to the FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) group.

FODMAPs are short-chain carbohydrates that are poorly absorbed in the small intestines, as such they end up in the large intestines.

This is how it might cause issues for people prone to acid reflux:

  • Onions are digested by bacteria producing gas.
  • This gas in the large intestines makes the stomach bloat, which increases the pressure on the stomach
  • An increased stomach pressure pushes stomach contents into the esophagus causing heartburn.

Consuming a low FODMAP diet was successful in reducing the osmotic load in the small intestines as well as gas production in the large intestines, all of which relieved reflux and heartburn symptoms.

Onion intolerance

Some people might be intolerant to onions. Frequent digestive symptoms – like bloating, diarrhea, and stomach cramps – might be a sign of onion intolerance.

Symptoms like bloating or cramps might also increase the risk of an acid reflux attack.

Such people are usually intolerant to other alliums as well, e.g. garlic or leeks.

It is worth noting that onion allergy is a different problem. An allergic reaction is not a digestive issue but an abnormal immune response to the proteins in certain foods.

Chest pain is not a typical allergic reaction. Hives, rashes, itching, or swollen body parts (lips, tongue) are more common.

If you think you might have an onion allergy, talk to an allergist and get yourself tested, because on rare occasions food allergies can have severe symptoms.

Cooked onions & GERD

While countless research studies have validated the association between raw onions and acid reflux, there is little or no information regarding the effect of cooked onions on acid reflux.

Some people think cooked onions may have a milder effect on acid reflux, though cooking may not be enough to stop all the reflux symptoms that onions provoke.

Besides, cooking does not significantly reduce the FODMAP content (does not change the FODMAPs from high to low) in foods. Thus, cooking would not change the fructan content of onions, thus the gas production and bloating will still be evident, which will still cause acid reflux.

Even though only anecdotal stories back up a possible milder effect of cooked onions on acid reflux, it might be worth a try.

Cooking often makes food somewhat easier to digest (e.g. potatoes) and therefore might decrease the chance of an acid reflux episode after eating onions.

How to relieve heartburn after eating onions?

Besides medications there are several natural ways to fight heartburn:

Those who experience heartburn regularly after eating onion should consider eliminating it from their diet:

GERD-friendly alternatives to onion

There are a couple of onion alternatives for people with acid reflux:

  • scallion (Allium sp.) or green onion
  • chives (Allium schoenoprasum)
  • leeks (Allium ampeloprasum)

all have a milder taste than onions and might be more suitable for people with GERD.

Final thoughts

Onions have a versatile use in many cuisines of the world, yet are potent triggers of acid reflux and heartburn in many sensitive people.

Cooked onions or alternatives, such as green onions, might be less likely to trigger heartburn.

Eliminating onions completely from the diet has proven to be an effective way of reducing and preventing reflux and heartburn episodes.

This article has been written by:

Meggy Jones

Expert Nutritionist and Food Scientist,
M.Sc. – Nutrition, ugent, Belgium