Sulfur (Sulphur) Burps, Rotten Egg Belching Foul Gas

Belching or burping is a digestive process where gas in the upper gastrointestinal tract (esophagus, stomach and first portion of the small intestine) is expelled into the environment. Although loud belching is not considered as a socially acceptable practice is most cultures, it is as normal as passing out gas from the rectum and anus (‘farting’ or flatulence).

Composition of Burps

Most of the gas that is expelled as a burp is actually swallowed air. This process of swallowing air is known as aerophagia. While it too it considered normal within certain limits, excessive air swallowing is a sign of some underlying problem. The rest of the gas may come from gas itself in carbonated beverages, as a byproduct of chemical digestion or is produced by bacteria in the gut.

The combination of these gases in addition to the foods that were most recently consumed gives burps the odor that it has, which can vary at different times of the day and with different meals. Burps do not have a pleasant odor. At best it is has little to no odor. Sometimes though it has an extremely foul smell but the odor of the burp in these instances could be a symptom of certain digestive disorders and diseases.

What are sulfur burps?

Sulfur (also spelled as sulphur) is often associated with a foul odor when it is mixed with other substances like hydrogen. With regards to sulfur burps, most of us understand it to mean rotten eggs. Hydrogen sulfide is the gas that is released from rotten eggs to give it the characteristic offensive odor, similar to stink bombs used in pranks and one of the components of flatus (‘fart’).

While this offensive odor is not entirely unexpected with flatus, it is often a cause for concern when it is smelled in burps. Since belching expels gas from the upper digestive tract it is logical to assume that the source of the sulfur burps lies in this area. The most likely sources are sulfur-containing foods and sulfur-producing bacteria.

Burping and belching

Foods High In Sulfur

Sulfur is an abundant molecule that is bound to various other molecules in nature. It is also common and relatively abundant in most foods like proteins. However, the focus should be on foods that have a high concentration of sulfur and compounds that can be digested to release hydrogen sulfide. Many of these foods are also the so called ‘gassy foods’.

Vegetables and Fruits

  • Avocados
  • Bananas
  • Beans
  • Broccoli
  • Brussel sprouts
  • Cabbage
  • Cauliflower
  • Chives
  • Collard greens
  • Garlic
  • Kale
  • Leeks
  • Lentils
  • Onions
  • Potatoes
  • Shallots
  • Soybeans
  • Split peas
  • Turnips
  • Yam

Meat and Other Proteins

  • All animal meat
  • Eggs
  • Fish
  • Nuts and seeds
  • Tofu

It is important to remember that many of these high sulfur foods are present in most diets yet sulfur or rotten eggs burps are not a problem for most people. The major factor here is that the movement of food through the gut usually means that high-sulfur foods do not spend a long period of time in the upper gut. Therefore the cause of sulfur burps are more likely due to some delay in the movement within the upper gut.

Causes of Sulfur (Rotten Eggs) Burps

Food that enters the throat is rapidly pushed down the esophagus to enter the stomach. Once within the stomach it can remain here for anywhere from 30 minutes to 3 hours as the stomach walls crush the food (mechanical digestion) and the stomach juices break down the food (chemical digestion). As a result a host of gases are released from food.

Eventually a liquid with small particles known as gastric chyme is pushed out of the stomach. It undergoes further digestion in the small intestine. The gastric chyme is pumped out of the pylorus of the stomach. When rotten eggs or sulfur burps occur it is usually because food ferments in the stomach. There are certain condition in which this fermentation is more likely to happen. Although minimizing high sulfur foods may help reduce the rotten egg burps in these conditions, ultimately the treatment needs to be directed at the problem.


Gastroparesis is a condition where the stomach empties very slowly because there is damage to the nerves or muscles of the stomach. It is believed to be mainly due to nerve damage as occurs in conditions such as long term diabetes (diabetic gastroparesis). However, sometimes gastroparesis occurs for no known reason (idiopathic gastroparesis). The vagus nerve may also be injured or severed during surgery which can then affect the pumping of food out of the stomach.

Pyloric Stenosis

Pyloric stenosis is a condition where the last part of the stomach is abnormally narrowed. It is mainly seen in infants and may be linked to genetic and environmental factors. Projectile vomiting is the main symptom and it can lead to dehydration. If left untreated the dehydration can in turn lead to deadly complications.


Certain microbes can reduce the sulfur in food to produce hydrogen sulfide, the same compound that is responsible for the rotten eggs odor. This may include the bacterium, Helicobacter pylori, which can infect the stomach and cause gastritis. It may also be seen with giardiasis where the protozoan (single-celled parasite) Giardia lamblia infects the bowels after being ingested in contaminated food and water.

Bacterial Overgrowth

There are many different species of bacteria that live in the gut and do not cause any disease. In fact these bacteria play a role in bowel health and are known as the normal intestinal flora. Sometimes bacterial populations may increase excessively. While it does not infect the gut it can cause a host if disturbances. Small intestinal bacterial overgrowth (SIBO) is one such case.

Maldigestion and Malabsorption

If the normal digestion and absorption of nutrients does not occur then there is residual nutrients for bacteria to feed upon. Usually this is not a problem in the upper gut but presents with lower bowel symptoms. This may be seen in conditions like pancreatitis, pancreatic insufficiency, gallbladder disease, celiac disease, inflammatory bowel disease and food intolerances such as lactose intolerance.


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