Do Girls Fart? The Science of Flatulence Explained

Every healthy person passes gas, women and girls included, because it is a built-in byproduct of digestion rather than a habit or a choice. The idea that women don’t fart is a social one, and many women work harder than men to hide it.1The Society Pages. Do Girls Fart? The Science of Flatulence Explained

How Women’s Gas Compares With Men’s

In a careful count of healthy volunteers’ gas over a day, women and men expelled about the same total amount.2PubMed Central. Investigation of normal flatus production in healthy volunteers That comparison involved only five people of each sex, so it shows no obvious gap rather than proving none exists. Gas output also swings widely between people and between days.

In a lab test where trained judges sniffed samples, women’s gas had more of the rotten-egg gas and scored stronger on odor, about 5.5 versus 4 on a 0 to 8 scale.3McDougall. Bad Farts? Meat Stinks! But men passed bigger volumes each time, roughly 119 ml versus 88 ml per pass.4McDougall. Bad Farts? Meat Stinks! Put together, the total amount of smelly sulfur gas in each pass came out about the same for both sexes.5McDougall. Bad Farts? Meat Stinks!

A smaller pass with a stronger mix can deliver about the same amount of smelly gas as a bigger, milder one. Diet differences between any two people matter far more for smell than sex does, and the odor scores are one small lab finding, a hint rather than a rule for every woman or man.

Anatomy differs a little too. On scans, women’s colons averaged about 7 cm longer than men’s, roughly 154 cm versus 147 cm.6PubMed Central. Bowel habits and gender correlate with colon length measured by CT colonography Longer colons were also linked with constipation in the same scans.7PubMed Central. Bowel habits and gender correlate with colon length measured by CT colonography A longer route may help explain why constipation and bloating are common complaints among women, though it hasn’t been shown to change how much gas is made.

Women are often taught early that bodily noises are unladylike, so they hide gas more. Hiding means others rarely notice, which reinforces the belief that women don’t do it. Holding gas until you’re alone doesn’t reduce how much is made, only when it comes out.

Why Everyone Makes Gas

Gas enters your gut when you swallow air and when bacteria in your large intestine break down carbohydrates you didn’t digest.8National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & Causes of Gas in the Digestive Tract The bacteria ferment those leftovers and release gases directly, or by feeding other bacteria that make gas.9Journal of Functional Foods. Intestinal gas production by the gut microbiota: A review Gases made inside the gut, mainly hydrogen, carbon dioxide and methane, make up about three quarters of what you pass.10PubMed. Insights into human colonic physiology obtained from the study of flatus composition So most farting comes from your gut bacteria, while swallowed air supplies mostly nitrogen and oxygen.11PubMed. Insights into human colonic physiology obtained from the study of flatus composition

Air gets swallowed in everyday ways. Eating fast and talking while chewing pull extra air down with each mouthful. Fizzy drinks add carbon dioxide directly, and chewing gum or sipping through a straw means you swallow more air than usual. Much of it comes back up as burps, so only part travels on to the colon.

Your bacteria are not the same as anyone else’s. Each person carries a different mix of gut microbes, shaped by diet and life history. Some people’s microbes make lots of methane, others more hydrogen or sulfur gas. That mix is why two people eating the same meal can end up with very different gas. The same fermentation of fiber also produces compounds that feed and support the gut lining.12PubMed Central. Dietary Fiber Intake and Gut Microbiota in Human Health

How Much Farting Is Normal

The amount varies a lot between people and depends heavily on what they eat.17Better Health Channel. Flatulence A day of beans or onions can push a normal person toward the top of the range.

To tell whether your own gas is unusual, count passes across a couple of ordinary days rather than judging from one big meal, because single days swing widely. Your own usual pattern matters more than any single number, so a sudden change is more telling than a high count. Gas on its own, without pain or other symptoms, is rarely a health concern.

What Makes Gas Smell

Most gas is odorless; the smell comes from trace sulfur gases.18PubMed Central. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour The main one is hydrogen sulfide, the gas that smells like rotten eggs, followed by two other sulfur compounds in much smaller amounts.19PubMed Central. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour The stronger a fart smells, the more hydrogen sulfide it tends to contain.20PubMed Central. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour

Bacteria decide a lot of this. Bacteria that make hydrogen sulfide compete with methane-making microbes for the same hydrogen in the gut.21PubMed Central. Methanogens and Hydrogen Sulfide Producing Bacteria Guide Distinct Gut Microbe Profiles and Irritable Bowel Syndrome Subtypes Whichever group wins out shifts your gas toward smelly or less smelly.

Some foods can make gas smellier. Sulfur-rich foods such as meat, eggs and cabbage-family vegetables give sulfur-producing bacteria more to work with. Garlic and onions bring their own sulfur compounds, which can add to the odor. Beans tend to raise how much gas you make more than how bad it smells.

Foods and Conditions That Cause Extra Gas

In lactose intolerance, the body lacks enough of the enzyme that digests milk sugar.22SN Comprehensive Clinical Medicine. Lactose Intolerance—Old and New Knowledge on Pathophysiological Mechanisms, Diagnosis, and Treatment Undigested milk sugar then reaches the colon, where bacteria ferment it into hydrogen, methane and carbon dioxide.23International Dairy Journal. Understanding the physiology of lactose intolerance and an insight on the recent trends on management strategies Bloating, cramping and flatulence follow a few hours after dairy.24SN Comprehensive Clinical Medicine. Lactose Intolerance—Old and New Knowledge on Pathophysiological Mechanisms, Diagnosis, and Treatment Still, symptoms only loosely track how much gas is made, so gas alone doesn’t explain how bad someone feels.25Journal of Nutritional & Environmental Medicine. Correlation between symptoms and gas production in lactose intolerant subjects. Can symptoms predict a diagnosis of lactose intolerance?

If you suspect a dairy link, cut out milk products for a week or two and note any changes. Then reintroduce a glass of milk and watch for gas within a few hours. Hard cheese and yogurt often cause fewer problems than milk.

Some gas-heavy foods cause trouble for clear reasons. Beans and lentils contain sugars that human digestion can’t break down, so bacteria in the colon ferment them. Onions, wheat and some fruits contain fermentable carbohydrates that behave in a similar way. Sugar-free gum and candy sweetened with sorbitol and similar sweeteners are poorly absorbed and feed gut bacteria too. Adding fiber gradually lets those bacteria adjust, with less gas.

Not all fiber is a gas trigger, though. Wheat bran produced only about a tenth as much gas as easily fermented sugars when mixed with stool bacteria.26PubMed. Effect of dietary fiber on intestinal gas production and small bowel transit time in man If bran seems to cause discomfort, the cause may be something other than gas.27PubMed. Effect of dietary fiber on intestinal gas production and small bowel transit time in man

Hormones, the Menstrual Cycle, and Bloating

Methane production in the gut shifted across the menstrual cycle, and the pattern differed in women on the birth control pill.28PubMed Central. Influence of menstrual cycle and oral contraception on taxonomic composition and gas production in the gut microbiome Methane-making microbes are linked with slower, more constipated bowels in animal studies.29PubMed Central. Hydrogen Sulfide Producers Drive a Diarrhea-Like Phenotype and a Methane Producer Drives a Constipation-Like Phenotype in Animal Models Changing gut gases across the month may therefore partly explain why some women notice bloating or constipation at certain times. Tracking symptoms against your cycle for a few months can reveal a pattern worth sharing with a doctor.

Sensitive guts add another layer. People with IBS (irritable bowel syndrome), a common gut disorder that causes pain and changing bowel habits, felt worse after a fermentable drink than others did.30PubMed. Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome Yet they made the same amount of gas as people without IBS.31PubMed. Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome In IBS, a gut that is extra sensitive to stretching causes the discomfort, not extra gas.32PubMed. Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome When sensitivity is the issue, cutting gas-making foods may help less than expected.

How to Reduce Gas and Odor

Avoiding poorly digested carbohydrates helps some people with bloating and gas.33PubMed. Intestinal Gas Enzyme pills, such as lactase for dairy or alpha-galactosidase for beans, can help.34PubMed. Intestinal Gas Activated charcoal helps some people.35PubMed. Intestinal Gas

Enzymes work best when used correctly. Take lactase with the first bite of a dairy food, not hours afterward. Alpha-galactosidase works on the sugars in beans and certain vegetables and does nothing for dairy. Neither helps with gas from swallowed air, which is better handled by habits: eat slowly, keep your mouth closed while chewing, swap fizzy drinks for still water, and skip gum and straws if belching and gas bother you. A gentle walk after meals helps gas move through.

For odor, bismuth subsalicylate, the active ingredient in Pepto-Bismol, cut rotten-egg gas released from stool by more than 95%.36PubMed. Bismuth subsalicylate markedly decreases hydrogen sulfide release in the human colon Charcoal-lined underwear pads or cushions can also reduce flatus odor.37PubMed. Intestinal Gas Bismuth turns stool black temporarily and isn’t meant for long-term daily use without medical advice. Reserve it for occasions, and ask a doctor before using it regularly.

Is Holding It In Harmful

Gas can pass through the gut wall into the blood, travel to the lungs and be breathed out.38drhussenbux.substack.com. What happens when you hold in a fart? On average more than half of gut hydrogen and methane leaves through the lungs.39drhussenbux.substack.com. What happens when you hold in a fart? Holding it in briefly is harmless, though it can cause temporary discomfort and bloating.

Occasionally gas signals a problem. Smells of gas and stool change with disease, and doctors are developing smell-based tests for conditions like Crohn’s disease.40PubMed Central. The Diagnostic Utility of Volatile Organic Compounds in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis See a doctor if gas comes with weight loss, blood in stool, ongoing diarrhea, or severe pain. A sudden lasting increase without a diet change, gas with fever, vomiting or a swollen hard belly, and new symptoms after age 50 or with a family history of bowel disease also warrant a check-up.