Belching, Bloating, and Flatus: Helping the Patient Who Has Intestinal Gas

David A. Johnson, MD


October 07, 2010

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Intestinal Gas: A Very Common Problem

Hello. I'm Dr. David Johnson, Professor of Medicine and Chief of Gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia. Welcome back to another session of gastrointestinal (GI) Common Concerns -- Computer Consult.

Today we'll talk about a very common problem that I personally see every day, and I'm sure you do in your patients as well. It's intestinal gas. What do we do with intestinal gas? How do we interpret the symptoms? When do we look at further testing in these people, and what do we do with treatment? That is the outline, the structure of what I'd like to address about a very common problem occurring in every one of our patients to some degree.

First of all, it's natural to have intestinal gas, and to pass gas by the rectum (flatus) is very common. It occurs in the average American about 13 times a day, and the volume in studies that have looked at this, anywhere from 200 cc to 2000 cc of rectal flatus is within the normal range. So it's not an infrequent situation.

Sources of Intestinal Gas

What does it really mean when we talk about intestinal gas? There are 2 basic things that I look at in somebody who comes in with intestinal gas. Is it belching? Is it flatus, or is it a combination? If it's belching, it's very simple because there are very few ways that you can just get gas in your upper GI tract.

Eating habits. One of the ways is to ingest it, so I always ask about carbonated beverages. The second way, however, is to swallow air, and this is very common. It may be by a learned behavior, because some people do this when they get nervous, so I ask, does it get worse when you have anxiety or stress? Second is the way that they eat. Do they eat rapidly, and do they slurp their food? Do they do things like sip through a straw frequently, because that gives them a bolus of air every time they suck the liquid; they actually take down a bolus of air as well. Then there are certain circumstances where people may not have good eating "utensils." They may not have well-fitting dentures. That's a very common situation as well. If they are smokers, they take a volume of air every time they inhale. If you are sucking on dietetic candies or really any hard candies or chewing gum, these may facilitate the repetitive swallowing that may not be natural, but in response to having that extra stimulation of liquid secretions accumulating in their mouth. So those are ways that you start to think about belching.

Abdominal bloating. If you think about rectal gas, or flatus, these patients will come in with obvious complaints of passing gas, but a lot of them will just have significant abdominal bloating. Some people will show you that they feel like they're pregnant, and this comes from men and women.

Recognize that this is something that people have dealt with for a long time. If you go back in history, actually Hippocrates made a comment that passing flatus or gas made one feel whole, so it was a prophecy of one of the great medical physicians that we have in our profession telling us that gas is very common and a natural process. In Rome, one of the emperors, Claudius, actually proclaimed that it was okay to pass gas anywhere in Rome. Unfortunately for flatulent Romans in 315 the emperor Constantine actually eradicated this and made it illegal to pass gas. So, again, the flatulent Romans were up the creek. Nonetheless, recognize that people have dealt with the passage of gas and bloating for a long time.

When I talk to somebody with rectal flatus or bloating, the first thing I think about is diet. The second thing I think about is diet, and the third thing I think about is diet. I'll talk about diet, and candies and gums and things like that -- something that was ingested because the gas is being made.

Rectal gas is methane and hydrogen and some nitrogen. Abdominal gas or anywhere in the GI system, there are only 5 gases that you can have, those 3 plus oxygen and carbon dioxide. Carbon dioxide for the most part is absorbed very quickly in the body so that tends not to be much of a problem. Oxygen is a very low component of intestinal gas. So we're usually dealing with methane, hydrogen, and nitrogen gas causing most of the GI distress.

Lactase deficiency. So let's go back to flatus. What do you ask about from a dietary standpoint? One of the first things I ask about is what is their normal diet? And do they have certain foods that exacerbate the gas?

We will find that a number of people are lactose intolerant. Lactase deficiency is very common. We see it more in African Americans, Puerto Ricans, and Asians. The prevalence increases with age. A normal person going forward who didn't have childhood problems or mid-adult problems may have it later in life -- with atrophy of the small intestinal villi, you lose the lactase enzyme, and you may not handle milk products as well. Typically we'll see diarrhea with lactase deficiency as well but not always. So ask about lactose tolerance. Do they have gas after they have cheese or milk or an ice cream sundae or something of that nature?

Lactase deficiency is a very common cause of gas, because the lactose is not broken down as it goes through the small intestine, and fermentable carbohydrates are delivered to the large intestine or the distal small intestine where a lot of bacteria live. These are now fermentable products, and this is the pathogenesis of the abdominal bloating and flatus that occurs with carbohydrate malabsorption or maldigestion. So ask about lactose intolerance.

Dietary sweeteners. The second thing I ask about is what kind of sweeteners are they using? This is a very important, simple point, but I don't want you to forget it. The artificial sweeteners, by nature of their design are deliverable without calories -- Equal® and some of the newer food additives that you see in the grocery store, like Splenda®. These are things that patients use routinely or may ingest products that have these component parts, and these are fermentable sugars as well. The reason they don't cause caloric intake is because they're not absorbed. They're isomers of glucose and so glucose that would have been absorbed now migrates down to the small intestine and large intestine as a nonabsorbed but fermentable sugar. You'll find that these patients have a very, very predictable response with gas. So I would ask about that and about foods that they may be ingesting that also contain these [sweeteners]. A lot of dietetic foods have them.

A lot of dietetic foods will also put in mannitol or sorbitol because they are also nondigestible carbohydrates, meaning they don't add calories, but they get to the cecum and to the right colon as fermentable sugars. A lot of dietetic candies have mannitol in them so patients who are chewing gum (and again because they are chewing gum, think about belching) with sorbitol or the mannitol in the gum as a noncaloric sugar may also be causing problems as it gets in the gut -- dietetic mints are the same way.

Legumes and vegetables. Next, ask about food products that they're using, and ask specifically about the foods.

Legumes or beans are very classic for causing gas. The 2 sugars that are in beans are stachyose and raffinose, and we just don't have the digestive enzymes to metabolize [these sugars]. Beans are probably the best studied food product that we have, and are something that will cause predictable problems in the majority of people. Stachyose and raffinose are also in some other vegetables but to a lesser degree than legumes, but you'll find them in things like broccoli and cauliflower, potatoes, and sweet potatoes. These foods are very common exacerbants in some patients. Onions will do the same.

So I take a very detailed history, and if I am sending a patient out I'll ask them to [record a diet] history for the next time I see them. We'll look at the food products that he or she ate, and find what we can single out and potentially avoid as it relates to decreasing the complaints [of intestinal gas].

Fiber and fiber supplements. Now we hear a lot about fiber, and we're told that we should eat more fiber.

Some of the fiber supplements, the methylcellulose-type supplements that you see in Metamucil® or Citrucel®, are soluble fiber. Soluble fiber means that it dissolves and becomes a kind of a gelatinous material, but when it gets to the colon it's now fermentable. The nonfermentable fibers are things like wheat germ or some of the vegetables, but it's much less common [for these to produce gas]. A patient who is eating a lot of fiber may actually be precipitating a lot of this gas. A lot of the sugars, especially complex sugars obtained in fruits and other food products that are very healthy foods, may actually be exacerbating the patient's gas.

So think about the dietetic things, and about the consumption of fiber, fruits, and vegetables. You may modify some of these foods and see if the patient has dramatic improvement. I've had a lot of patients improve just by removing Splenda® or Equal® from their daily diet; this changes the component of their discomfort and makes them feel considerably better.

Evaluation of Intestinal Gas

Work-up. When should we worry about these patients, and when do we initiate further workup? I start pretty simply by [asking] how long has this been bothering you? If it's a sudden onset or if their complaint of bloating is unilateral, don't forget organs on the right side such as appendicitis or gallbladder disease -- it would be predictable that they should have pain and maybe some diarrhea. Those would be [the red flags that] warrant further testing: imaging testing, computed tomography scans, diagnostic testing with endoscopy.

Celiac disease. Think about celiac disease. It's undiagnosed in a lot of patients. Typically they present with the diarrheal syndrome, but gas and bloating from maldigestion can occur very early, and so it's not unreasonable to consider getting a celiac profile in these patients and looking at their baseline labs to make sure nothing else is amiss.

Treatment Options for Intestinal Gas

Once you've told the patient that you're going to focus on diet and lifestyle, [and if necessary], get their dentures fixed; [they should avoid] chewing gum and candies that they suck on during the day. You can potentially now send them out with a list of things that they can do on their own.

Anti-gas agents. Medications that are potentially helpful here, include Beano®, which is a product that helps digest stachyose and raffinose, is only really helpful in patients who [are ingesting] fiber that contains those sugars (beans, and to a lesser degree vegetables).

Another product that you might want to add is simethicone, which is very helpful for upper GI gas. It breaks up some of the component gas that forms in the stomach, but it only helps upper GI complaints.

For rectal gas, the addition of charcoal is helpful in some people, taking it before and after a meal. Patients seem to have some benefit. It may change some of the odor of the flatulence and to a lesser degree the volume of flatulence or the frequency of the flatulence.

Probiotics. I find that there are rare, but increasingly common circumstances where I add a probiotic, something that potentially may give the bacteria a little bit more of an advantage by changing the natural flora that are causing the problems. A lot of times it becomes an imbalance between the good and bad bacteria, if you will, in the host.

So I'll frequently recommend yogurt. Recognize that even in lactose-deficient patients, yogurt is okay. Not the frozen kind but the live culture yogurt. And I'll have them take this 2 or 3 times a day and potentially start their morning with a good fiber cereal. I recommend All Bran® for my patients; I have them mix it with yogurt and that seems to be a nice start on the day, and is a low challenge at least with respect to intestinal gas.

There are growing occasions where addition of a probiotic -- and in this circumstance I'm talking about things that like Align® or VSL#3® -- may have some benefit in these patients. I think it's reasonable to offer a trial of one of these for a month or so to see if this [provides any] adjunctive benefit. I'm using these increasingly in my practice.

Rifaximin. In circumstances where the patient may have a little diarrhea or is just frustrated that they're not getting any better, I'll use rifaximin.

Some preliminary experience suggests that this may be a way of resetting the normal bacteria so you knock out the bad overgrowth bacteria. In particular, we're talking about small intestinal bacterial overgrowth. A short course (2 weeks) of rifaximin, 400 mg 3 times a day for 14 days. It's hard to get it justified just for gas, but if the patient also has diarrhea, insurance companies tend to acquiesce pretty quickly. You will see more and more application of this medication when irritable bowel studies are published later this year.


So just to recap, in talking about intestinal gas, think about food, food, food.

Think about products that contain the complex carbohydrates. Recognize that elimination of these complex carbohydrates is very helpful in the majority of patients. Probably the only carbohydrate that doesn't really cause gas is rice so if your patient is looking for a starch, this is something that they can substitute. Think about food products that contain a nondigestible carbohydrate; such as Splenda®, Equal®, hard candies, and dietetic gum that the patient may be chewing as well.

Think about habits, such as smoking, repetitive air swallowing, or sipping. Think about carbonated beverages. Think about what exacerbates symptoms in these patients. Provide them with a list of foods that may be [causing intestinal gas]. I'll send the patient home with a food diary and charge them to come back in 4-6 weeks, and give me some overview of [their dietary habits].

For treatment, think about probiotics -- more and more is emerging on this. Give them a short course, or perhaps a short course of rifaximin may be of help in some of the more recalcitrant patients. I think you'll find that by reassuring patients that it's gas and it's normal, but perhaps not normal for them, and that you may be able to modify it, you'll have a happy patient. And, in fact, I think you'll find that some of these suggestions may apply to you.

So I'll leave that to you. I look forward to discussing another topic with you shortly in the future. Thanks again for listening.