First the bread went, then the milk, then sugar, then anything with a label longer than four words. Each cut helped for a week or two. Then the bloating came back, and the list of foods you were afraid of kept growing.
Every list of foods that upset your gut tells you to cut something, then tells you to eat more plants to make up for it. That second part is where the trouble usually starts. Each cut helped because it took away work your gut was struggling with, and the work it struggles with most is the part of the plate it can't digest at all.
What your gut can and can't digest
Your gut is built in two halves. The stomach and the small intestine do the digesting, and most of what you absorb from a meal is taken in there. Meat, fish and eggs suit that first half well: acid and enzymes break their protein and fat down, and the small intestine takes nearly all of it in before anything reaches the bacteria further down.
Fibre is the opposite. By definition it's whatever in a plant your own enzymes can't break down, so it passes through the small intestine untouched and lands in the large intestine. There, bacteria ferment what they can, and fermentation makes gas. A gut full of gas feels exactly like the bloating you were trying to cut away.
The fibre advice has a starting point. Denis Burkitt, back from years in Uganda, saw that many Western diseases were rare in African hospitals and put it down to diet and lifestyle, and his 1979 book Don't Forget Fibre in Your Diet became an international bestseller. What he compared, though, were whole ways of life, not fibre on its own.
That's why "eat more fibre" can make a bloated gut worse. In Singapore, a group of 63 patients whose constipation had dragged on for years were advised to drop fibre, and some dropped it entirely. For them the bloating and straining disappeared, and trips to the toilet went from one every three to four days to daily. The six who kept their high-fibre diet were all still bloated, all still straining, and still went about once a week.
The plants that ferment
Some plant sugars behave like fibre. They slip past the small intestine and ferment further down, and they go by the clumsy name FODMAPs, short for fermentable sugars and sugar alcohols. Onions, garlic, wheat, beans, lentils, apples and pears are packed with them. Put 30 people who have irritable bowel syndrome on a diet low in them for three weeks, and their gut symptoms scored about half what they did on an ordinary Australian diet, with less bloating, less pain and less wind.
Beans and the cabbage family carry another one, raffinose. No human gut makes the enzyme to digest it, so it travels down intact, and the bacteria waiting there turn it into the gas beans are famous for.
Normal is anywhere from 8 to 20 times a day, about half a litre to a litre and a half in all, and what you eat decides the amount more than the bacteria do. Cut what reaches them to ferment, and the volume falls. Gas once had a stage career, too. From 1892 Joseph Pujol filled the Moulin Rouge breaking wind to music, with the Prince of Wales and Sigmund Freud among his audiences, though his act ran on air he drew in and let out on cue, with no beans involved.
Wheat is where cutting gets confusing. In a test with 59 people convinced that gluten was their problem, each was given, without knowing which, gluten, fructans (the fermentable sugars in wheat) or a dummy powder, the fructans brought on the symptoms, and gluten did no worse than the dummy. Wheat brings more than fructans to the table, too: it's a seed that defends itself chemically, and Why You Feel Better Without Wheat lays out the rest. Coeliac disease is the exception that needs a test first, since testing needs gluten still in the diet to give a true answer.
What's hard on every gut
Factory food sits near the top. When healthy adults ate food containing a common emulsifier, cellulose gum, also called carboxymethylcellulose, for 11 days, their gut bacteria became less varied and meals left them a little more uncomfortable, and in two of the seven, bacteria pushed into the inner mucus layer that's meant to stay sterile. You'll find it in ice cream, mayonnaise, drinks, and reduced-fat and gluten-free products.
That mucus layer and the gut wall under it are what "leaky gut" talk is about. The barrier and its permeability are real, and diet affects them. "Leaky gut syndrome" as a diagnosis of its own belongs to alternative medicine, and the home tests and supplements sold for it tell you little. That lining renews itself every four to five days, which helps explain why a gut given a break can settle so quickly.
Sugar mostly gets absorbed high up, so little of it reaches the bacteria further down. Fructose is the exception in large amounts: even a healthy small intestine absorbs somewhere between 25 and 50 grams of it at a sitting, so a big glass of juice, several spoons of honey or a bag of sweets can overflow it, and the rest ferments into gas and bloating.
Artificial sweeteners are less innocent than their zero calories suggest. When 120 healthy adults took one of stevia, aspartame, sucralose or saccharin daily over a fortnight, each one shifted their gut bacteria, and saccharin and sucralose pushed blood sugar higher after a meal. Sugar alcohols, the sorbitol, xylitol and maltitol in sugar-free gum, mints and "diet" sweets, aren't fully absorbed either, so they pull water into the bowel and ferment there. A pack of sugar-free mints can bring on bloating and diarrhoea by itself.
Some medicines leave their mark. A course of antibiotics clears out useful bacteria along with the harmful ones. Tablets that cut stomach acid change the gut's bacteria as well: in their regular users, a fifth of the bacterial groups differed from those of people not taking them. If you come off them, do it slowly and with whoever prescribed them, because a sudden stop can bring back heartburn that wasn't there before. After eight weeks on acid tablets, volunteers who had never had heartburn reported acid symptoms on stopping three times as often as those given a dummy.
Your stomach needs its acid
Acid is the first tool your gut uses on protein, and a stomach short of it is common. Over the age of 60, more than three in ten people make little or no stomach acid. A drink with the meal makes the job harder. When healthy adults drank a single glass of water, the acid in their stomach was diluted within a minute in ten of the twelve. Drink between meals, and let the acid you have do its work. Acid is also one of the guards that keeps bacteria out of the small intestine. When too many settle there, a condition called small intestinal bacterial overgrowth, or SIBO, the result is bloating, pain and loose or slow bowels, and low stomach acid and long use of acid tablets are among its known risks. Indigestion? Your Stomach May Need More Acid, Not Less, linked below, covers the signs of running short.
What's personal
Lactose is the clearest example. About two-thirds of adults in the world make less of the enzyme that digests milk sugar than they did as children, though a gut short of that enzyme can usually still handle about 12 grams of lactose at a sitting, roughly a cup of milk, without much trouble. Hard cheese carries almost none: a 30-gram piece of cheddar holds about 0.02 grams. Goat's and sheep's milk carry as much lactose as cow's milk, so switching animals changes little.
Your gut runs its own nervous system, some 500 million nerve cells, five times as many as your spinal cord, and it talks to your brain constantly. Stress is one of the things that sets irritable bowel symptoms off. How you eat counts too. Eating fast, gulping fizzy drinks or chewing gum all day fills the gut with swallowed air. A slower meal, sitting down, is one of the cheapest gut treatments there is. If that link between gut and mood is what you want to understand, by Emeran Mayer explains it in plain language.
If your gallbladder has been taken out, go up on fat gradually. Diarrhoea after the operation is a known problem, because bile reaches the gut faster than it's reabsorbed, and bile-acid diarrhoea, which affects about 1 in 100 people, is easily mistaken for irritable bowel syndrome, so get checked if loose stools carry on.
Why the gut goes quiet on meat
Bloating for years, then meat, fish, eggs and not much more, and within days the gut goes quiet. That relief is real, and the reason is simple. Meat is digested almost completely in the small intestine, so little of it reaches the bacteria further down. With almost nothing to ferment, the gas stops, and the bloating goes with it. For someone who reacts to onions, beans and wheat, the change can feel like a switch being flipped. When 2,029 adults on a carnivore diet answered a survey, 95 per cent said their overall health had improved, and only 3 to 5.5 per cent reported gut complaints. by Paul Saladino makes the whole case for this way of eating.
It also makes the cleanest elimination test there is. Start from a gut that has gone quiet, reintroduce plant foods singly, and the ones that cause trouble show themselves quickly. The ones that pass can stay on the plate if you want them there, as a side dish, never the base of the meal.
Some suspects don't have to be guessed at. A hydrogen breath test can show whether you're failing to absorb lactose or fructose, and a similar test is one way of checking for SIBO.
The open question is the long run. Your gut bacteria live on what reaches them, and on meat alone that's next to nothing, so their numbers and their range shrink. What that means over years is still an open question. What Happens to the Body When You Remove Most Plant Foods, linked below, goes through what is known so far.
Fermented foods, and what capsules miss
If you want to give your gut bacteria something, fermented food does more than fibre. Over a 17-week test, healthy adults who added fermented foods such as yoghurt, kefir, sauerkraut and kimchi found their gut bacteria growing steadily more varied while blood signs of inflammation dropped. The group put on a high-fibre diet ended with the same range of bacteria they started with.
The ones that help contain live cultures, so look for yoghurt and kefir that say so, or make your own kefir with , and buy sauerkraut or kimchi from the chilled section. A jar that sits unchilled on a shop shelf for months has usually been heated, and the heat kills the bacteria. Which Fermented Foods Are Still Alive When You Eat Them? sorts the live ones from the dead.
Probiotic capsules are a different story. Their bacteria survive the trip, but they rarely settle in: in volunteers whose gut lining was sampled directly, the capsule strains took hold in some guts and not in others, and left only a passing mark. They do have one job. Taken alongside a course of antibiotics, they lowered the odds of antibiotic diarrhoea by roughly two-fifths. Afterwards, though, they slowed the gut's own recovery compared with doing nothing, so food is the better way to rebuild.
Heartburn has its own list
Acid reflux follows different rules from bloating. Large meals, fatty meals, alcohol, coffee and chocolate can all set it off, and so can lying down soon after eating. Give yourself about three hours between the last meal and lying down. If your problem is burning rather than bloating, a smaller, earlier dinner does more than any food list.
When things slow down
The usual answer to constipation is more fibre, and for a gut that's already bloated it can be the wrong way round, as the 63 people in Singapore showed. If fibre is already high and things are still stuck, try less of it before you try more. Moving your body helps your bowel move too, and regular exercise is a standard part of treating constipation.
When it's more than food
Some symptoms call for a check-up before any diet change. Get checked if you see blood in your stool or it turns black, if the scales drop without you trying, if symptoms wake you at night, if swallowing becomes difficult, or if your bowel habits change and stay changed for more than a few weeks. The same goes for bowel trouble with tiredness that could mean you're low in iron, or a family history of bowel cancer. Bowel cancer is turning up more often in people under fifty, so age alone is no reason to wait.
Strip it back before you add
The enemies list gets the order wrong. It cuts one food at a time from a plate built on plants, then piles more plants on to make up for it. Start from the other end: a plate your gut can digest, meat, fish and eggs done in butter or tallow, no sugar, and water kept for between meals. Then try plants again singly, with a few days between each, and keep only the ones that keep the peace.
This week, try three days of meat, fish and eggs, drink between meals, and write down each evening how your gut felt that day.
Wondering what happens when the plants go for good? What Happens to the Body When You Remove Most Plant Foods — what changes, what improves, and what's still an open question.
Is it burning and heaviness after meals more than bloating? Indigestion? Your Stomach May Need More Acid, Not Less — why the acid may be too low, and how to help your stomach do its job.
Know someone who's cut half their diet and is still bloated? Send them this. They may have been cutting the wrong half.
Tried something here, or got a question it didn't answer? Write to us at contact@allforlife.club. Your questions shape the next articles.
Disclaimer: This article is general information. For advice about your own digestion, medication or health, talk to a qualified health professional. If you have any of the warning signs described above, or you think you may have coeliac disease or irritable bowel syndrome, get checked before making big changes to what you eat.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to books and products we would recommend without the commission.
Sources
Wikipedia. Small intestine. en.wikipedia.org
Wikipedia. Dietary fiber. en.wikipedia.org
Wikipedia. Denis Parsons Burkitt. en.wikipedia.org
Ho KS, Tan CY, Mohd Daud MA, Seow-Choen F (2012). Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms. World Journal of Gastroenterology 18(33):4593–4596. doi.org/10.3748/wjg.v18.i33.4593
Halmos EP, Power VA, Shepherd SJ, et al. (2014). A Diet Low in FODMAPs Reduces Symptoms of Irritable Bowel Syndrome. Gastroenterology 146(1):67–75.e5. doi.org/10.1053/j.gastro.2013.09.046
Wikipedia. Raffinose. en.wikipedia.org
Wikipedia. Flatulence. en.wikipedia.org
Wikipedia. Le Pétomane. en.wikipedia.org
Skodje GI, Sarna VK, Minelle IH, et al. (2018). Fructan, Rather Than Gluten, Induces Symptoms in Patients With Self-Reported Non-Celiac Gluten Sensitivity. Gastroenterology 154(3):529–539.e2. doi.org/10.1053/j.gastro.2017.10.040
Wikipedia. Coeliac disease. en.wikipedia.org
Chassaing B, Compher C, Bonhomme B, et al. (2022). Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome. Gastroenterology 162(3):743–756. doi.org/10.1053/j.gastro.2021.11.006
Wikipedia. Carboxymethyl cellulose. en.wikipedia.org
Wikipedia. Intestinal permeability. en.wikipedia.org
Wikipedia. Leaky gut syndrome. en.wikipedia.org
Wikipedia. Intestinal epithelium. en.wikipedia.org
Wikipedia. Fructose malabsorption. en.wikipedia.org
Suez J, Cohen Y, Valdés-Mas R, et al. (2022). Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell 185(18):3307–3328.e19. doi.org/10.1016/j.cell.2022.07.016
Wikipedia. Sugar alcohol. en.wikipedia.org
Imhann F, Vich Vila A, Bonder MJ, et al. (2017). The influence of proton pump inhibitors and other commonly used medication on the gut microbiota. Gut Microbes 8(4):351–358. doi.org/10.1080/19490976.2017.1284732
Reimer C, Søndergaard B, Hilsted L, Bytzer P (2009). Proton-Pump Inhibitor Therapy Induces Acid-Related Symptoms in Healthy Volunteers After Withdrawal of Therapy. Gastroenterology 137(1):80–87.e1. doi.org/10.1053/j.gastro.2009.03.058
Wikipedia. Achlorhydria. en.wikipedia.org
Karamanolis G, Theofanidou I, Yiasemidou M, et al. (2008). A Glass of Water Immediately Increases Gastric pH in Healthy Subjects. Digestive Diseases and Sciences 53(12):3128–3132. doi.org/10.1007/s10620-008-0301-3
Wikipedia. Small intestinal bacterial overgrowth. en.wikipedia.org
Wikipedia. Lactose intolerance. en.wikipedia.org
Wikipedia. Enteric nervous system. en.wikipedia.org
Wikipedia. Irritable bowel syndrome. en.wikipedia.org
Wikipedia. Aerophagia. en.wikipedia.org
Wikipedia. Cholecystectomy. en.wikipedia.org
Wikipedia. Bile acid malabsorption. en.wikipedia.org
Lennerz BS, Mey JT, Henn OH, Ludwig DS (2021). Behavioral Characteristics and Self-Reported Health Status among 2029 Adults Consuming a "Carnivore Diet". Current Developments in Nutrition 5(12):nzab133. doi.org/10.1093/cdn/nzab133
Wikipedia. Food intolerance. en.wikipedia.org
Wastyk HC, Fragiadakis GK, Perelman D, et al. (2021). Gut-microbiota-targeted diets modulate human immune status. Cell 184(16):4137–4153.e14. doi.org/10.1016/j.cell.2021.06.019
Wikipedia. Sauerkraut. en.wikipedia.org
Zmora N, Zilberman-Schapira G, Suez J, et al. (2018). Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated with Unique Host and Microbiome Features. Cell 174(6):1388–1405.e21. doi.org/10.1016/j.cell.2018.08.041
Hempel S, Newberry SJ, Maher AR, et al. (2012). Probiotics for the Prevention and Treatment of Antibiotic-Associated Diarrhea: A Systematic Review and Meta-analysis. JAMA 307(18):1959–1969. doi.org/10.1001/jama.2012.3507
Suez J, Zmora N, Zilberman-Schapira G, et al. (2018). Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. Cell 174(6):1406–1423.e16. doi.org/10.1016/j.cell.2018.08.047
Wikipedia. Gastroesophageal reflux disease. en.wikipedia.org
Wikipedia. Constipation. en.wikipedia.org
Wikipedia. Colorectal cancer. en.wikipedia.org