Although the mention of stomach gas problems, such as belching, flatulence, bloating and “gas pains” often elicits some degree of amusement, all of us have gas in our intestinal tract and must expel it in some way.
Some individuals are very sensitive to the effects of gas collections in the stomach and intestinal tract and may develop significant discomfort.
If such complaints are troublesome and persistent and do not respond to simple measures, such as change in diet, a visit to your doctor could be helpful.

The gas brought back by belching comes entirely from swallowed air. We all swallow some air when eating food and drinking liquids. Most of the gas mixes with the stomach content and either enters into the small intestine or is belched back.
The air that enters the small intestine is either absorbed or it may continue through to the large intestine and is then passed rectally. Individuals may swallow more air (and thus increase stomach gas) if they have a post-nasal drip, chew gum, have poorly fitting dentures, suck on hard candies or smoke tobacco. Drinking carbonated beverages (soda or beer) or eating rapidly can also increase stomach gas.
The food we choose to eat can influence the amount of gas passed rectally. Although most of our food intake is absorbed in the small intestine, some foods, such as cauliflower, broccoli, cabbage, baked beans, and bran are incompletely digested.
They are then broken down by bacteria in the large intestine, causing the formation of gas. A high roughage diet is important to promote bowel regularity, but excessive roughage or fiber may lead to bloating and increased flatulence.
When increasing the amount of fiber in your diet, do so gradually, allowing your intestinal tract time to adjust.Milk sugar (lactose) requires an intestinal enzyme (lactase) for digestion. When individuals lack this enzyme the lactose in milk and other dairy products enters the large intestine where the lactose is broken down by bacteria, producing gas.
Although milk is an excellent source of protein and calcium, many adults experience abdominal bloating, gas and diarrhea after consuming milk sugar. Persons from Asia and Africa are often extremely intolerant to the smallest
quantity of dairy products.

Everyone passes some rectal gas, although the volume of gas is different each day. Much of the flatus comes from the nitrogen found in the air one swallows. The remainder of the flatus volume is the result of carbohydrates which are not absorbed in the small intestine and are broken down by bacteria in the large intestine.
Therefore, the amount of flatus represents a combination of swallowed air and poorly absorbed carbohydrates. The unpleasant order of flatus is due to other gases, such as hydrogen sulfide, which is produced by the bacteria.

Individuals with a long history of occasional gaseousness and abdominal discomfort need not seek medical attention. A change in the location of abdominal pain, significant increase in the frequency or severity of symptoms, or onset of new symptoms in individuals over the age of 40 are some of the reasons to see your doctor.