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Your digestive tract is said to be your second brain. It’s where many or your brain chemicals such as serotonin are made and is home to over half of your immune system in the form of healthy bacteria and gut associated lymphatic tissue. You don’t want to mess around with your gut, though many people do, often every time they put something in their mouth.

Digestive problems are a common complaint for most people. Whether it’s heartburn, bloating, gas, indigestion, constipation, or even more serious symptoms associated with diseases such as Crohn’s, ulcerative colitis, or diverticulitis, often food plays a major role. Unhealthy bacteria, yeast, other types of fungus, parasites, and inflammation can result in an unhealthy immune system, and a poorly functioning body, including your brain. So yes you are what you eat, and your physical and mental performance relies heavily on what you consume.

Although food allergies and sensitivities exist in many people due to an immune reaction to the protein of a food, there are other types of reactions present that cause gut problems. One such problem is perhaps even more prevalent than food allergies, and perhaps the reason for many food allergies as well as a host of gut problems including dysbiosis. This sensitivity has to do with the carbohydrates (sugars) in foods that create bacterial overgrowth.

Small Intestine Bacterial Overgrowth (SIBO) is a chronic bacterial infection of the small intestine.  The infection is often of the bacteria that normally live in the gastrointestinal tract but have abnormally overgrown in a location not meant for so many bacteria. Often SIBO occurs because of dysbiosis – where there is an imbalance of the beneficial bacteria (as well as yeast) with other types of harmful bacteria, yeast, and sometimes even parasites – but also because those bacteria are living off what you’re feeding them.

This healthy bacteria overgrowth in our gut can interfere with normal digestion and absorption of food. Leaky gut syndrome is a name given when there is damage to the membrane of the digestive tract which leads to malabsorption of nutrients such as iron, vitamin B12, vitamins A & D, as well as other nutrients. The bacteria consume and literally live off food unable to be absorbed in the digestive tract, so it grows and grows and as they do, they expel gas which causes abdominal bloating and pain, constipation, and diarrhea. Undigested food particles can enter through the gut lining causing an immune reaction resulting in food allergies and sensitivities. Auto-immune reactions such as Celiac disease and rheumatoid arthritis may be a result of poor digestion from food allergies or SIBO in some people. The gut bacteria can also enter the bloodstream, burdening other areas of the body and creating a toxicity resulting in pain, fatigue, and a host of other symptoms including those neurological, such as memory problems, dementias, and learning disabilities.

FODMAPs refers to Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are a collection of molecules found in food that can be poorly absorbed by some people. When the molecules are malabsorbed in the small intestine of the digestive tract, they then continue along their journey along the digestive tract, arriving at the large intestine, where they act as a food source to the bacteria that live there normally. The bacteria then digest/ferment these FODMAPs and can cause a host of symptoms as noted previously.

Fermentation of undigested food happens normally in the colon, and although there is a gradient of bacterial colonization in the small intestine, significant fermentation in the small bowel is abnormal and results in SIBO. Since bacteria eat the starch contained in all grains, SIBO offers an explanation why avoiding all grains, not just gluten grains, helps many people even though they may not be “allergic” to gluten. And also, many people omit gluten from their diet and eat “gluten-free” foods, but see no change in their symptoms. This could possibly be because many gluten-free products contain bean and lentil flours, which is a basically switching one FODMAPs (galactan) for another (fructan).

FODMAPs, especially free fructose, may contribute to SIBO. Fructose malabsorption is defined as the incomplete absorption of fructose in the small intestine, followed by the delivery of fructose to the distal small intestine and colon, where it contributes to rapid fermentation and resultant abdominal bloating. The absorptive capacity of fructose varies from person to person.

The allowed foods are mainly those foods that people ate before agriculture began, and one I recently discussed in the Paleo-Type diet. The diet we evolved to eat over millions of years was predominantly one of meat, fish, eggs, vegetables, nuts, low-sugar fruits. Our modern diet including starches, grains, pasta, legumes, and breads has only been consumed for a mere 10,000 years. In the last hundred years the increase in complex sugars and chemical additives in the diet has led to a huge increase in health problems ranging from severe bowel disorders to obesity and brain function disorders. We have not adapted to eat this modern diet as there has not been enough time for natural selection to operate. It therefore makes sense to eat the diet we evolved with.

Here’s where FODMAPs are found:

  • Oligosaccharides (Fructans and Galactans)
    • Fructans are oligosaccharides made of fructose molecule chains that are completely malabsorbed because the small intestine lacks hydrolases to break their fructose-fructose bond. For this reason, fructans can contribute to bloating, gas, and pain. Wheat accounts for the majority of people’s fructan intake. Other high fructan foods are globe artichokes, Jerusalem artichokes, asparagus, beetroot, chicory, dandelion leaves, garlic (in large amounts), leek, and onion.
    • Inulin and fructooligosaccharide (FOS) are also sources of fructans, and are added to many foods to enhance their fiber content and also to many probiotic supplements to encourage the growth of friendly gut bacteria. Interestingly though it has a negative effect for many people unknowingly. I rarely use probiotics with FOS or inulin because so many people react to these products.
    • Galactans are oligosaccharides containing chains of the sugar galactose. The human body lacks the enzymes to hydrolyze them into digestible components, so they are completely malabsorbed. Dietary sources of galactans include lentils, chickpeas, kidney beans, black-eyed peas, broccoli, and soy-based products.
  • Disaccharides (Lactose, Sucrose)
    • Lactose is milk sugar so all cow, goat, and sheep milk should be avoided as well as those products made from them which still has some sugar content, such as yogurt. Butter is okay since it’s just the milk fat. Cheese will vary per individual based off tolerance and sugar content. (The bacteria in the dairy convert the milk sugar lactose to lactic acid during fermentation into cheese.) Low-lactose cheeses including Swiss, Parmesan, Gouda, Colby, provolone, cheddar, Edam, Muenster, and Monterey Jack may be okay for some. **Interestingly, there can be a few different problems with cow milk. Many people are allergic to the protein (casein, rather than the whey) in dairy, giving them various symptoms. Other may be lactose intolerant where they lack the enzyme lactase to break down the milk sugar, lactose, often resulting in the common digestive complaint of diarrhea. And yet another problem may be the FODMAPs relationship as the bacteria in the gut eat the lactose, fermenting the sugar and giving the person a host of symptoms. Damn dairy!
    • Sucrose is table sugar (the white stuff) and should be limited or removed based upon individual tolerance. This includes brown sugar, raw sugar, turbinado, and cane and beet sugars.
  • Monosaccharides (Fructose, rather than glucose, in this case)
    • Higher fructose (fruit sugar) content is found apples, mango, pears, watermelon, peaches, sugar snap peas, canned fruit, dried fruit, and fruit juice. This is where you should investigate your individual tolerance to certain fruits and find your threshold level. In other words, you may be able to eat one apple, but not two apples or an apple with another FODMAPs food, such as cheese. High fructose corn syrup and agave should always be avoided due to their excessive fructose levels. Honey may or may not be a problem in the FODMAPs diet, especially in low dietary amounts and depending on the source and quality of the honey. Honey with higher fructose content tends to crystallize more than honey with less fructose and more glucose.
  • Polyols are also known as sugar alcohols (Sorbitol, Mannitol, Maltitol, Xylitol and Isomalt). Most are too large for simple diffusion from the small intestine, creating a laxative effect on the GI tract. They are found naturally in some fruits and vegetables and added as sweeteners to sugar-free gums, mints, cough drops, and medications. Polyols will produce osmotic diarrhea when consumed in quantities above an individual’s personal threshold, (especially when they are added as a sweetener), or in combination with other FODMAP sources. Apples, apricots, avocado, cherries, raspberries, longan, lychee, nectarines, peaches, pears , plums, prunes, mushrooms, cauliflower, mushrooms, snow peas, and almonds all contain somewhat higher levels of polyols (xylitol). The added sugar alcohols should be removed 100% from the diet.

Omitting FODMAPs from your diet if you feel you are sensitive can have dramatic effects on your entire health. Energy levels often increase, sleep improves, blood sugar becomes more balanced, (since an overgrowth of bacteria in the gut is no longer consuming many of your carbohydrates for energy), mood improves, and many other symptoms improve as your gut heals. Ideally you should refrain from all the FODMAPs for at least a couple weeks, longer if your symptoms are not fully resolved by then, but continue to improve. After a good two weeks of being symptom-free you can try adding in various FODMAPs foods to check your sensitivity and tolerance levels to certain foods. You may find that you can’t eat a food such as wheat at all, but perhaps can handle some dairy periodically such as a particular cheese, for example. In essence, you figure out your FODMAPs threshold – the point at which your symptoms return but you must first clear them out of your diet one hundred percent!

Some physicians recommend using herbs, supplements, and even medications (antibiotics) to help rid the body of bacteria overgrowth quicker than just refraining from the foods that feed it. I have seen this beneficial, but also see it to be very individualized. In some patients I have found they respond well to herbs such as Uva Ursi and Goldenseal, whereas other patients supplements such as biotin and betaine hydrochloride work well. However, whatever the case, total omission of FODMAPs is necessary – the supplements just tend to help resolve symptoms quicker especially if they “accidently” snuck a FODMAPs food into their diet.


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  1. LLB permalink

    This actually makes perfect sense and I’m glad that a connection has been made. Our bodies are not supposed to be eating “high fructose corn syrup”. God didn’t make our internal organs to accept those types of foods that were developed in a lab as opposed to outdoors with sunlight and rain. I am going to give this a try to see if it will relieve the pain and other symptoms I have been experiencing for years.

  2. Doan permalink

    What do you think of NOW’s NAC supplements with Molybdenum?

    • Not familiar with their brand of NAC. But I see regular L-Cysteine to work much better than the acetylation form in general, even though everybody says that’s not the case. I think it’s because nobody studies just the L-CYS form.

  3. Donna permalink

    I’ve been suffering with digestive issues for over 40 years, including IBS and 3 acute attacks of diverticulitis. My GI suggested colon resection surgery, which is not sitting well with me. I just had a consultation with a dietician or is helping me to work on a FODMAP meal plan that I’m starting this week. Have you seem improvements with diverticulosis managements for patients that implement FODMAP? I do feel that gas & bloating have greatly contributed to my diverticulitis attacks so this seems to make sense. I’m seeing lots of recommendations to use FODMAP for IBS but haven’t been able to find much information on how it can be useful for my condition.

    • I have seen several patients who were set to have surgery to remove some or all of their colon and none of them had to go that route. Part of the treatment I use is dietary changes (sometimes FODMAPS Diet), as well as other therapies; it’s based upon the individual situation.

    • Thaddeus Buttmunch MD permalink

      I have an elderly relative with Diverticular issues; has nausea and lower left abdominal cramps and history of IBS. Cottage cheese, apple sauce and veggie chopped liver are tolerable, as well as hot tea with honey. Needs generic benefiber in the morning and miralax at night to “go.” I have given him antibiotics and asacol, bentyl and tylenol for spasms and pain and zofran for nausea (which does not seem to work well) If it were ME I’d take medical marijuana but he can’t stand the taste-HELP!

      • Tough one but could be a yeast/fungus issue. You might try some herbs like coptis or goldenseal or some straight berberine. If you’re not familiar or comfortable with those types of therapies then send me and email and I’ll see if I know any holistic docs in your your/his area.

  4. karen permalink

    Thanks for the helpful article. After much mis-diagnosis from my doctors and becoming horribly ill from Prilosec which was prescribed, I finally found research on SIBO and believe my problems stem from that. The FODMAP diet has helped me tremendously.

    Can you recommend any FODMAP friendly products for coughing and nasal congestion from allergies?

    • No because that would be very individualized. Someone who is allergic to one FODMAP food and other allergic to a different one.

  5. adrian permalink

    Interesting article. however raises for me a basic question.
    As looking for treatments for Crohn disease – was inclined to adopt SCD / GAPs diet. Fodmap concept is similar – however there are major gaps in the list of allowed / not allowed foods – for example – honey, sugar, rice (!), potatos etc… – in this sence they tend to contradict each other. Whats your view?

    • It’s because of the sugar type (per FODMAP). You have to see what works best for you but in my experience FODMAPS is often the most ideal.

  6. Grace permalink

    I’ve read a lot of info about the FODMAPs diet being helpful for IBS but haven’t seen much about its effectiveness for Crohn’s or ulcerative colitis. Do have an experiences with these IBD?

    • I have a lot of experience treating patients will all of those conditions. And yes typically FODMAPS is the most ideal diet for them all. Not always, but usually.

  7. Charlotte from Denmark permalink

    Good news about the honey, but you have the sugars the wrong way round there, glucose is the one responsible for crystallization, and the lowering of FODMAPs. Whereas fructose keeps honey liquid and is the “evil” one.
    Honey from canola plants (Rapeseed) is lowest in FODMAPS.

  8. Jayden permalink

    Would taking probiotics while on FODMAPS be a bad Idea?

    • Not sure. If they have FOS like a lot do then yes. But ideally the FODMAPS cleans up the gut so you don’t need probiotics.

  9. mack permalink

    Hi Dr. gangemi

    I have severe ulcerative colitis, and been suffering pretty bad for the past 10 yrs, I’ve been on every medication possible to control the disease and they all seem to lose their effect , on humeira and a lot of steroids right now, I’ve managed to figure out a couple of foods that trigger my flare ups, such as spicy, fatty meats, alcohol and dairy but cant really come up with a diet that will give me piece of mind, can u help me?

  10. Suzanne permalink

    Does your site have a FODMAP chart? Just starting on this diet and see so many conflicting charts online. My naturopath gave us a Paleo low- fodmap and a Gut-Healing and Symptom-Mgmt. Protocol for SIBO (undiagnosed medically). These 2 conflict as well as other FODMAPs we are seeing. Going crazy here trying to figure out what are FODMAP certains!

  11. robert quigley permalink

    i have been suffering for year with acute intermittent porphyria and as a result much of the pain is abdominal pain , gas and bloating. lately everything i eat seems to cause stomach pain and nausua . i eat healthiy foods but lately can’t hold any food and losing my appetitie
    i have every medical test endo scope , colonoscopy, mri etc, nothing showing other than minor gastristis. do you think i have alegerys

    can you suggest

  12. Katie permalink

    Dear Dr Gangemi
    My stool tests showed an overgrowth of bifidobacterium & no lactobacillus & eubacterium. I’ve started taking straight lactobacillus. What can I do to correct this imbalance? I’ve read SIBO can be caused by an imbalance of good bacteria too. I have upper gut gas, reflux & burping every few minutes. Low Fodmap doesn’t seem to help with the upper gas. I have been on Rifamaxin for one month, and had FMT last year.

    • I’d suggest you find a physician who can assist you figuring out what to take and how to help best correct the problem.

  13. jenny permalink

    I’m 48 years old, an athlete, and have been vegetarian (love wheat, all veggies, etc.) for almost 30 years (occasional seafood). I am, quite honestly, the definition of a healthy person. A few years ago I was diagnosed with Stage 1 Colon Cancer, which was shocking to me; unbeknownst to me, my grandmother had colon cancer in her mid 80’s so this might be why I got colon cancer (?) Before my diagnosis I had minor IBS symptoms. I had colorectal surgery and it went well; yet, I continue to have IBS symptoms which mostly includes lots of gas. I’m considering going on the FODMOP diet to see if eliminating wheat, gluten helps me. Do you feel that a vegetarian diet can actually promote colon cancer?

    • I’m not going to go that far out on a limb and say that but I don’t personally think a vegetarian diet is a healthy one. Sure, there are always exceptions but in my opinion, and experience, humans tend to do better on a meat “Paleo Diet”.

      I wish you well and a full recovery! :)

  14. ellie permalink

    I have always assumed that raw vegetables irritate my colon and trigger my cramps from colitis. Are you saying that if they are the ‘right’ veggies, that shouldn’t happen?

  15. Arthur permalink

    Per last post i read, what would be the wrong veggies and the rite veggies. Also I was diagnosed with Candida and H pylori. Have severe sinus issues. bloating, gas and ;poor digestion. Also constipation. I have head aches. blurred vision, joint pain back ache, weight, and every time I eat theses reactions get worse for about an hour or so but here lately it is continuing and will not subside. sometime it I drink a lot of water this helps with the allergies. My stomach or small intestines are constantly rumbling gurgling and making noise. I give up I do not know what to do. Can not sleep much and feeling like you know what..

  16. Max W permalink

    How about extreme fatigue? It’s almost like being knocked out.
    I’ve been avoiding gluten for two years. Then early last week, after going to a restaurant; I slept almost half of the next 48 hours. I figured it was an increased sensitivity to gluten cross contamination. Then mid week I had another bout of fatigue, this time I noticed it was the day after eating a meal heavy in onion and garlic. Today, again, I ate a meal w one onion and 3 cloves of garlic, and promptly spent 1/2 of the next 8 hours napping.
    Yes, there is some odd bowel issues going on; gas and diarrhea and whatnot, but not near as dramatic as this extreme fatigue. I’ve also noticed peripheral muscle weakness, and also some decreased sensory perception. Thing is; my diet has always been heavy on onion and garlic.
    Wrenches in the mix are I’m three weeks off 28yrs of a heavy nicotine habit, and about two weeks off Advair.
    Got any thoughts?

  17. Natalie permalink

    Im 41yrs old with IBS (constipation with diarrea), High Cholesterol and seronegative inflammatory arthritis. Since I have inflammatory arthritis I was not sure if I should eat a Mediterranean diet or FODMAP diet, Paleo. These are the issues I problems I’m running into:

    1) I need to gain weight not loose weight, too many food restrictions
    2) most vegtables and whole grains will cause severe constipation even on Miralax 2x day
    3) I would like to be able to get off Miralax, I’ve been on it for 10yrs. No matter what type of fiber it will cause severe constipation.
    4) I would like a diet that works for both IBS and inflammatory arthritis

    Please help any suggestions would be great! I’m tired of researching, all I’m getting is confused and conflicting information.

    Thank you!

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