Beans & Gas: Clearing the air

Beans and Gas

More than a decade ago, the Quarterly Journal of Medicine published a review entitled: “Vegetarian Diet: Panacea for modern lifestyle disease?” The answer was in the affirmative, noting those eating vegetarian appear to have less obesity, high blood pressure, diabetes, heart disease, high cholesterol, cancers, kidney disease, maybe less stroke, less age-related vision loss, less diverticulosis, fewer gallstone and of course, less constipation. But after going through the laundry list of benefits, the researchers did identify two drawbacks of a plant-based diet: 1) the risk of vitamin B12 deficiency, which I’ve covered previously, and 2) increased intestinal gas production. So on one hand, we have half of the top 10 causes of death in the United States, and on the other, flatulence.

Let me start off by saying that intestinal gas is normal and healthy. When patients present to physicians complaining of too much gas, they are typically instructed to go home and keep track for a week. “Although this may sound complicated,” wrote researchers in a gastroenterology journal, “we have found that patients rather enjoy keeping such a record.”

Americans report passing gas an average of 14 times a day, with the normal range extending up to a frequency of 22 times daily. Many people who think they have too much gas fall well within the normal range, concludes famed flatologist Michael Levitt, M.D., “and they simply have to be informed of their ‘normality.'”

Wondering who funded this research? You may be surprised that the real ground-breaking work in this area was done by NASA in the 1950s—our grandparents’ tax dollars hard at work. NASA was genuinely concerned that astronauts might suffocate, or some spark would ignite the methane. So papers with names like “Recent Advances in Flatology” represent space age research! As one NASA research scientist recommended, “it may prove advantageous to select astronauts…who do not normally produce large quantities of flatus.”

I’ll never forget the first time I lectured on the subject. I asked if anyone in the auditorium cared to venture a guess as to how many times a day the average person passes gas. I was expecting the students would posit maybe 5 or 10 and then I could wow them with the fact that no, the norm is more like once every waking hour, up to 22 times a day. But the first guess? 200. OK, so maybe some people do have too much gas! For those wanting to cut down on emissions, here are some tips (I’ll try not to be too long-winded :).

Flatulence come from two places: swallowed air, and fermentation in the bowel. Things that can cause you to swallow extra air include gum chewing, ill-fitting dentures, sucking on hard candies, drinking through a straw, eating too fast, talking while you eat, and cigarette smoking. So if the fear of lung cancer doesn’t get you to quit smoking, maybe fear of flatulence will.

The main source of gas, though, is the normal bacterial fermentation in our colon of undigested sugars. Dairy products are a leading cause of excessive flatulence, due to poor digestion of the milk sugar lactose, though even people who are lactose tolerant may suffer from dairy. One of the most flatulent patients ever reported in the medical literature was effectively cured once dairy products were removed from his diet. The case, reported in the New England Journal of Medicine and submitted to the Guinness Book of World Records, involved a guy who, after consuming dairy, experienced “70 passages in one four-hour period.” Cutting the cheese, indeed.

Other poorly digested sugars include sorbitol and xylitol in sugar-free candies. The fizziness in soda is carbon dioxide, which gets absorbed by our gut, but the high fructose in the soda’s corn syrup may be another culprit. Cruciferous vegetables may also contribute (kale-force winds?). Some grains can do it—the word pumpernickel stems from Middle German and means, roughly, “goblin that breaks wind.”

Beans have been christened the musical fruit, but could it just be a lot of hot air? A randomized controlled crossover study published last week, “Perceptions of flatulence from bean consumption among adults in 3 feeding studies,” concluded “People’s concerns about excessive flatulence from eating beans may be exaggerated.”

Noting that “An increasing body of research and the 2010 Dietary Guidelines for Americans supports the benefits of a plant-based diet, and legumes specifically, in the reduction of chronic disease risks,” they started people on pinto beans, black-eyed peas, or vegetarian baked (navy) beans. During the first week, 35% reported increased flatulence but that fell to 15% by week three, 5% by week five, and 3% by week eight. Much of the bad rap for beans grew out of short-term studies in the 60’s that didn’t account for our body’s ability to adapt.

Long-term, most people bulking up on high-fiber foods do not appear to have significantly increased problems with gas. In the beginning, though, “A little bit of extra flatulence,” reads the Harvard Health Letter, “could be an indication that you’re eating the way you should!” The buoyancy of floating stools from trapped gasses can in fact be seen as a sign of adequate fiber intake. The indigestible sugars in beans that make it down to our colon may even function as prebiotics to feed our good bacteria and make for a healthier colon.

Even if at first they make us gassy, beans are so health-promoting that we should experiment with ways to keep them in our diet at all costs. Lentils, split peas and canned beans tend to be less gas-producing. Tofu usually isn’t an offender. Repeated soakings of dried beans and tossing the cooking water may help if you boil your own. Worse comes to worst, there are cheap supplements that contain alpha-galactosidase, an enzyme shown to break up the bean sugars and take the sail out of your wind.

Odor is a separate issue. The smell appears to come primarily from the digestion of sulfur-rich foods, so to cut down on the stench, experts have recommended cutting back on foods such as meat and eggs (hydrogen sulfide is called “rotten egg gas” for a reason). In “Contribution of Dietary Protein to Sulfide Production in the Large Intestine” researchers found that meat-eaters generated as much as 15 times the sulfides as those eating vegetarian.

There are healthy sulfur-rich foods, such as garlic and cauliflower. If you’re about to embark on a long trip in a confined space after a big meal of aloo gobi, Pepto-Bismol® and generic equivalents can act as a windbreaker by binding up the sulfur in your gut to eliminate odors, but should be used only as a short term solution due to the potential for bismuth toxicity with chronic use.

Then there are the high tech solutions, such as carbon fiber odor-eating underwear (cost: $65),  which were put to the test in an American Journal of Gastroenterology study that included such gems as “Utilising gas-tight Mylar pantaloons, the ability of a charcoal lined cushion to adsorb sulphur-containing gases instilled at the anus of eight subjects was assessed.” Assessed, that is, by a panel of fart-sniffing judges. And the name of the charcoal lined cushion? The “Toot Trapper.”

To reiterate, though, intestinal gas is normal and healthy. No less than Hippocrates himself was quoted as saying “passing gas is necessary to well-being.” As one chair of gastroenterology wrote in a review of degassing drugs and devices (and yes, Dr. Fardy is a real name), “Perhaps increased tolerance of flatus would be a better solution, for we tamper with harmless natural phenomena at our peril.”

 – Michael Greger, M.D.

Reposted from One Green Planet

Image credit: net_efekt / Flickr

  • Michael Greger M.D.

    Please be sure to leave any questions or comments you have below, and check out all the videos on beans!

    • Stacey

      Hello Dr. Greger – I recently discovered your site and LOVE the information you provide. I wasn’t sure where else to post this, I do realize this thread is a bit dated. I’ve read many conflicting articles on beans – one camp seems to believe them to be a superfood, while the other condemns them as a food not fit for human consumption due to their high lectin content. If indeed beans must be cooked to reduce their toxicity to tolerable levels, are they really as healthy as they are claimed to be? I’m a bean lover, but have given them up because a nagging voice in my head makes me tend to agree that any food that must be cooked and/or processed before it can be consumed by humans is perhaps not the best food for me to be eating. Do you have any thoughts or insight on this? Your response is much appreciated!

  • Dr Fardy! Bwahaaahaaaaahaha!

    …..I think I have been hanging out with my 4 sons too long.

  • JJ

    I laughed my way through this one. You have a fun way of presenting science.

  • Mike Quinoa

    Kale-force winds—I love it. Lately I’ve been getting lazy and just eating my kale raw, much like you would a stalk of celery. Dr Greger, I believe you advocate making a green smoothie out of the kale for maximum nutrient absorption. Is my laziness costing me nutrapoints?

    • DrDons

      Hi Mike,
      You probably would get a bit more nutrients with proper cooking of the Kale. However you don’t loose much and the important thing is to eat your greens. Doing smoothies is a convenient way to get nutrients. You can view previous videos for more information.. Raw Food Nutrients and Best Cooking Methods.

    • JJ

      Mike: I remember one of Dr. Greger’s videos that talked about needing to get some fat with your greens in order to get certain nutrition. In other words, if you eat it raw without say nuts or rubbing a little oil in, then you are missing out on some good nutrition.

    • JJ

      Ah, I found the video if you want to check it out for yourself:

  • Mike Quinoa

    Thanks DrDons and JJ for your informative replies :)

  • Vegan Epicurean

    Dr. G,

    I recently heard that the reason humans produce gas after eating beans is because they contain raffinose which is a starch that is poorly digested due to a lack of the enzyme galactosidase. The MD claimed that adding baking soda to the soaking liquid reduced the raffinose. Have you heard anything about this?


    • Michael Greger M.D.

      Yes indeed, research dating back more than 25 years (“Effect of Processing on Flatus-Producing Factors in Legumes“) found that adding baking soda to the soak water of dried beans before cooking (about 1/16 teaspoon per quart) significantly decreases the content of the raffinose family of sugars. The study I profile here in Beans and Gas: Clearing the Air that concluded “People’s concerns about excessive flatulence from eating beans may be exaggerated” used canned beans, though, which I find to be much more convenient. If you have the time, though, it’s hard to imagine a better nutritional bargain than dried beans, peas, and lentils.

      • Don’t forget to rinse the beans after soaking in baking soda… it isn’t supposed to be included in the final product. Also, adding carrots to your cooking the beans is another old fashioned way of reducing gas when cooking beans.

  • Vegan Epicurean

    Thanks Dr. G. for the quick reply and the links. You are the best! I knew you would know and would be happy to share. :-)


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  • Brian

    I’m a vegan who eats mostly plant based whole foods(some processed) diet and I still have foul smelling farts. I think I surpass the normative 22 farts per person per day as well. Since I was a child I’ve always had an excess of gas and even taking medications has never helped. I’m sure shifting from a carnivorous diet to a plant based diet has helped my overall health but I’ve never been able to decrease the odor or consistency of this natural(but embarrassing) bodily function. 

    • DebPate

      basically 5 common causes for excessive flatulence:

      1.   Consuming too many carbs

      2.   Consuming indigestible foods, this is
      an individual issue i.e. lactose intolerance is a common problem

      3.   Excessive enzymes: again an
      individual issue two people can eat the same meal and only one of them will develop
      gas, simply because his intestinal tract contains more enzymes. It all depends
      on the amount and type of bacteria in the large intestine.

      4.   Chewing food and swallowing air:
      chewing food properly alleviates the work the intestinal tract has to do i.e.
      less gas. Swallowing more air than normal ie. chewing gum will do just the

      5.   Intestinal infections: eating
      contaminated food or drinking contaminated water will cause intestinal tract
      problems; I assume this is not the problem.

      Cutting the
      amount of carbohydrates and avoiding foods that you know cause you problems can
      be very helpful and again I assume you have tried this to some extent.  Chamomile, peppermint, sage and marjoram are
      the common herbs that help alleviate flatulence.  Hot pepper and ginger can also be helpful.  Over-the counter Bean-O is touted to work but
      I’m always wary of over-the counter products.

    • Emilyc615

      I have a similar problem and have found that consuming more fiber (in the form of a supplement) and using magnesium supplements for a kind of laxative effect is really helpful. The problem appears to be transit time. I calculated that it took about three days from the time I had a meal until it left my body, and that gave the food a lot of time to go rotten in my gut, causing really uncomfortable stuff to happen. Someone else on this website recommended a book called “Cure Constipation Now” which is where I got the idea to consume more fiber and use non-irritating laxatives to speed things along.

    • Danillo

      I know vegans who say that they don’t think they can eat legumes at all because of bloat, and they worry about not consuming their essential aminoacids. I know soaking the legumes before cooking is usually recomended, but could sprouting have an even better effect on their diggestion?

      • Dina

        Oh, definitely, sprouting helps a lot. IT makes everything easier on the gut, and nutrients are more readily absorbed. I love my sprouted stuff!

  • Aloe may help.  It is easy to find the juice in health food stores these days.

    Also, James Duke recommends carminative herbs:  allspice, cloves, cornmint, caraway, dill, fennel, horsebalm, peppermint, sage, and thyme.

  • Smilenstein

    May I suggest fart absorbing pads …if you have a problem. My sister sent me this link one day and I nearly died laughing. Read the comments and ratings. Hillarious.

  • Kirbonite

    I try to wash beans.. Dr. Klaper suggest that has comes from the hemi-cellulose (sp?) coating.. I find canned beans don’t cause problems but in an effort to decrease sodium I starting soaking and boiling.. I fart more now..   however, I did mix in some kale and mushrooms.

    • Tonya CatLady

      Soak and rinse dried beans several times before cooking and eating rice with beans resolves the tooting.

  • Love your posts Dr. Greger… well written, and humorous!

  • Jennifer Green

    I found this interesting and hilarious! I read portions of it to my kids, and they were laughing so hard. My son is now an aspiring flatologist.

  • Carol

    Not only are you adorable but you make me laugh out loud!! Thanks for the realization that I am normal! :)

  • Betsy

    Dr. Greger, your puns in this article had me laughing so hard that I was crying! Thanks for the good info and for a great laugh as well!

  • Selçuk Danişment

    It is common knowledge to cook beans and lentils with a spoonful of cummin (in Turkey) to get rid of the gas..

  • Ruby

    You REALLY make learning and reading about health a fabulously fun experience with lots of belly laughs Doc. If you’ve seen my many posts now since I found this site, you know I don’t agree with all and I am a bit of a wordy gurdy, but I want you to know my “professional” ;) disagreement/parrying detracts naught from my general appreciation and respect of your work and my recognition of magnanomy of this site. Yur awesome.

  • Frenchhorn

    This is the funniest essay ever. My sister’s doctor told her not to eat fiber. Sad.

  • Lee

    70 farts in a 4 hour period? Yep, I could do that. My family and I have not eating animal products in over 3 years now and although the rest of my family is not afflicted, I am plagued with emission of the most offensive olfactory insults. I love legumes and cruciferous vegetables. I don’t drink soda and don’t eat garlic very often. Bean-O did nothing to help. I tried the vegan equivalent to Bean-O and it also did nothing to help. Thankfully my family accepts me as “Farty Pants”, but I work indoors and find this gas problem to be cruel and unusual punishment for those around me. I easily pass 5 toots an hour during waking hours. I love the foods I eat and eat a very healthful whole food plant-based diet. Is it possible that I have some abnormal gut bacteria? Putting “toot trappers” aside, what else might I try to help? Three years should have been enough time for my gut to adjust. (According to my nutritional journal I am consuming about 40 or more grams of fiber a day.) Any ideas?

    • Alice

      There is an internal deoderant used by people with colostomies that should cut the odor.

  • Predrag Nikolić

    Dear Sir, I don’t know if you are familiar with the Natural Hygiene phenomenon in your country, synthetized by the late Dr. Herbert M. Shelton (1895-1985), one of the few divine Americans I know. The Man taught about the importance of proper food combining for the digestion and asymilation of our food. Talking of legumes, some of which, like soy, are almost 50% carbohydrates and 50% protein, the compounds that cannot digest at the same time at the same place, the timing in digestion here being of very high concern, the Man advised only green salad with legumes, a very simple meal, in order to allow this complex food to digest properly. He explained the process of digestion of beans like this: It needs to be thoroughly chewed and mixed with salivary enzyme ptyalin, the first phase of digestion of starches. He explained that our stomach glands will “wait” for a while for the salivary action in digesting the starch of the beans to take place, “knowing” that the ptyalin will be destroyed in a highly acid environment, and after a while, excretes the highly acid juice in order to digest the bean protein content. So, eating many other things, like bread, starchy vegetables, vinegar and who knows what else with beans, will surely produce digestive problems. And let me repeat Dr. Shelton’s words that if properly combined, our food will not produce fowl gas, and can eliminate even the need for toilet paper, if anyone still uses it. That I could witness myself in my own experimenting with food combining.
    Thank you for your good work and contribution to a healthier society.

  • Renilde

    Dear Dokter Greger, Would you know if there is any science behind the idea of ‘proper’ food combining for optimal digestion? The basic idea put forward is that different foods require different pH levels to digest properly, and they all have different transit times in de gastrointestinal tract. The belief is that eating certain food combinations – specifically protein-rich foods combined with carbohydrate-rich foods – are harder to digest, which decreases nutrient absorption and promotes gas, bloating and the buildup of toxins. Is there any scientific truth in those assumptions? Thank you so much!

    • Joseph Gonzales R.D.

      Good question. I think some people feel different (more or less energetic, bloated, or satisfied, etc) when they eat certain foods or combinations of foods, but there is no research I am aware of to suggest a protein-carb combo for optimal digestion. Dr. Greger has shown research on animal protein and carbohydrates leading to increased risk of diabetes, so perhaps the digestive process is subpar in that environment? We know certain food combos like antioxidants/vitamins and fat sources, iron and vitamin C, pepper and turmeric, can influence each another However, I am not sure about pH levels I would think stomach acids tears through any protein and denatures it and packages it as needed for use. Dr. Greger mentions stool pH and colon cancer and how fiber creates butyrate and other health promoting short chain fatty acids. So I feel optimal digestion stars with optimal fiber, like 40 grams, and we have plenty of research on fiber.

  • Roy Lingenfelter

    Dear Michael Greger M.D., My family and I are new to the world of the plant based diet. We are about a month to 6 weeks in and doing well. However, when we started my wife was hoping that it would help with foul smelling gas. She has severe issues with dairy and sometimes even with meat giving her foul gas. I assured her that I was convinced it would help but it might take some time. She still has pretty bad gas and is frustrated. Nothing seems to give me foul gas, infact you can rarely even tell. What could the difference between our GI tracts be and do you think she may see some difference in the future if she remains on a plant based diet?
    Kind Regards,
    Roy T. Lingenfelter

    • squinkie04

      Try avoiding onions. It works for me.

    • squinkie04

      Including onion powders of all sorts.

  • Can’t Have It Both Ways

    Sure this thread is old. So what? I would venture to say most of you buy into the narrative and corruption in “climate science”. Put another way, raise your hand if you have the courage and intellectual honesty to be a skeptic to the corrupt hysteria. If you have the backbone to challange The Cult of Glo-Bull Warming. And yes there is heavy corruption in “Glo-Bull Warming” for a variety of reasons, often overlapping. Political reasonsl, personal greed, paychecks, scamming grants, career etc.

    So the article ends with the premise that the methane flatulance of the soon to be over ten billion humans is “harmless”. Yet the GW cult says methane is one of the supposed major contributors. Which is it? Harmless or a horrifically dangerous pollutant that poses a dire threat to thr planet?

  • Nick Presidente

    Pretty sure this wasn’t a video because it was too hiiarious to narrate

  • B. Recht

    I am cooking all the beans & lentils this way: beans I soak with apple cider vinegar for 24 hrs, then rinse well
    & cook with a pinch of Bicarbonate of soda.
    Lentils – I soak for 4-6 hrs, also with Apple cider vinegar then rinse & cook with a pinch of bicarbonate of soda.
    All the various varieties cook much quicker & can be frozen.
    Never had a problem with wind!

  • Ferdinand Cadu

    Try to add some subheadings to this article (and others too), kinda hard to read without them.. hope you understand.

  • Courtney R

    Dr. Gregor, on the topic of digestion, what are your thoughts on the theory of food combining for good digestion? Eating fruit alone on an empty stomach, carbs/veg only meals or protein/veg only meals, not mixing starch and protein, not mixing fat and protein etc. Since this I have read this info I have refrained from my afternoon snack of fruit because I don’t want it to “catch up” with my lunch and “ferment”. Is this non-sense or is there truth to eating fruit first thing in the morning and not combining certain foods for great digestion at meal time? Thanks!

  • rada

    In the 70’s I lived in a vegetarian commune with a group of about 60-80 like minded people. The majority of the group were between the ages of 18 – 25, of mixed gender and mainly from a Caucasian background . Members of the group reported significant issues with flatulence, especially from beans , and it did not diminish over the 2 year period. Most of the females experienced severe issues including bloating.

    The Winham and Hutchins study;“ Perceptions of flatulence from bean consumption among adults in 3 feeding studies “, referenced by Dr Greger to suggest that issues with bean caused flatulence are over-stated and will diminish with time, does not provide strong evidence to support this claim …… the number of participants is too small to be a valid sample, the amount of beans consumed was small and the study relied on self feedback to draw a conclusion (self-reporting is subjective and prone to error).

    Other studies that measured actual frequency, volume and gas content of flatulence, in larger controlled study groups, show that flatulence is correlated to fibre intake.

    Other studies, particularly those on IBS and FODMAP response suggest that:

    – gas production in the gut, from fermentation of undigested carbohydrates, is normal and probably has healthy outcomes;

    – a percentage of people have abnormal and excessive gas production, and other issues including bloating and diarrhoea;

    – the primary cause is undigested carbohydrates and the carbs that are behind the gas production varies from person to person (generally they are the FODMAP foods that nutritionists recommend people with ‘sensitive stomachs’ should avoid e.g. fructose, certain oligosaccharides, artificial sweeteners and some other sugars) ;

    – the gases produced are the by-products of bacteria that feed on the undigested food …. these include Hydrogen, Carbon Dioxide, Methane and the pungent Hydrogen Sulphide;

    – The amount and type of gas produced by the bacteria, when presented with the same food varies i.e. the bacteria can be more or less active per gram of undigested carbs;

    – gases produced are not only emitted as flatulence but they also enter the bloodstream and exit via the skin and the breath. Breath testing can be used to test individuals susceptibility to various foods;

    – breath testing indicates variations of adverse response to difficult to digest carbs are dependent on genetics, gender and racial background (in one study the largest production of gas was produced by Caucasian females)s from undigested food

    – in some people other food intolerances also cause excessive gas e.g. dairy products for people who are lactose intolerant;

    – some cases of food indigestibility are due to a lack of specific enzymes (it is unlikely that the inability to digest certain foods because of inherited enzyme deficiencies food will improve with time);
    – response is dependent on the amount eaten. Small amounts are manageable but at a certain level the response increases almost exponentially;

    – continued incidents of extreme anti-reaction to indigestible foods may cause long term adverse health effects e.g. damage to the lining of the gut.

    It seems likely that over time the digestive systems of various racial groups adapted to the food types prevalent in their diet (studies show people with Asian heritage are the least likely to produce gas after eating beans).
    It is also possible that the problem is exacerbated if the offending foods also contain certain types of sulphur that increase the percentage of Hydrogen Sulphide in the gas, hence making the flatulence smell worse,

    Anecdotal evidence also suggests food that has not been adequately digested or certain food combinations can also exacerbate the problem.

    Food preparation e.g. soaking and sprouting, can reduce the amount of indigestible carbs in some foods. In other approaches additives are used e.g. bicarb soda, vinegar or some herbs e.t.c however most of these rely on anecdotal evidence for support.

    In other cases the use of enzymes can over come the problem e.g. enzymatic treatment of milk to reduce lactose.

  • Daniel

    Well after reading the article i guess flatulence is a sign of good health. Although it should decrease with time i in a stage that i cant stop having them. Ive been on a plant based diet for a year and 4 months and ive been having this problem ever since. How do i reduce this problem? Its making me really uncomfortable on public places daily, i need to leave the room, the odor is really bad and one last thing to add. I go to the bathroom once every two days. sometimes daily and i know this last one is bad. What can i do?

  • Sham Prasad

    Fermentation in the bowel is the main cause Yes I do agree this point which is mentioned in the this article. I want to add to this that meat is the another cause for this fermentation. I have read this on one site recently here They explained same thing about fermentation. Swallowed air is yet another but I do not think so. I want to give some top 5 foods to aid digestion here Thank you nutrition facts for giving me this opportunity to express my views.

  • DonaBella

    Dr. I LOVE the way you write. You must be an expert writer to be able to present such fun in a serious topic as kale-force winds and “tak[ing] the sail out of your wind.” I laughed my way through reading your piece, as it really was a [pardon the pun] a windbreaker for me too. I actually looked up the issue as I cooked an entire 1 pound bag of dried bried/fava beans for dinner tonight and oh how delicious and buttery they were. But after 4 hours, man, oh man!!! Yikes! Just hold your hornet and run! But of course I do realize beans and cruciferous cookery can crucify one’s quiet evening moment even though they are healthy. I was just wondering whether there could ever be a way to not make the entire household run after i cook a healthy meal.