Farting! For such a ubiquitous activity, it's amazing how taboo it is. But should it be so? And are beans – a staple of a good vegan diet - really the villains of the piece?
It's a curiosity of British social etiquette that if you burp you say pardon, but if you fart, you say nothing and walk away... probably in the hope that no one has noticed! We never seem to grow out of being excruciatingly embarrassed by passing wind. Yet all of us do it, many times every day. Even women, though ours smell of roses!
The NHS states that most men fart 14-25 times a day, and most women between seven and 12 times a day. We pass wind mainly when sleeping and mostly in little puffs, not as the ripsnorters we all dread kabooming at a dinner party, or while canoodling on a date!
Life’s a gas
Ninety nine per cent of our farts are odourless and made from carbon dioxide, oxygen, nitrogen, hydrogen and sometimes methane but the one per cent that smell? We all know they can be deadly! The stinky bit is hydrogen sulphide, which smells like rotten eggs and although it’s a minute part of a fart, is so pungent that people can smell it at levels of 1 part in 100 million.
The foods which contain the most sulphur compounds which are converted by bacteria in your gut into hydrogen sulphide are red meat, dairy products, eggs, cruciferous veg, onions and garlic, beer, red and white wine, cider and dried fruits. The reaction can be severe! My friend’s son, Jack told me: “I ate eggs for breakfast, and believe it or not I was farting so much the teacher made me leave the classroom!” However, there is good news. The bacteria that make the pongy hydrogen sulphide are in much lesser numbers in those with a healthy vegan diet, than those on a meat and dairy diet.
Why do we fart?
When you swallow food, liquid or saliva, you also swallow small amounts of air, which collects in the digestive system. The gases have to escape and do so by burping out of your mouth (belching) and farting out of your anus (flatulence).
However, three quarters of your farts are gases made by microbes mainly in your large intestines. Think of it like this - bacteria fart into you and you fart out their farts. You have no choice. And in fact, farting is often the sign of a healthy gut, playing host to 100 trillion bacteria, fungi and archaea composed of 500 to 1,000 different species. You have an intricate and complex ecosystem inside you that needs feeding, and the gases they produce need expelling!
Purna Kashyap, a gastroenterologist at the Mayo Clinic, USA studies the gut microbiome and explains: "There are a lot of carbohydrates that we consume that our bodies don't have the enzymes necessary to digest; these end up in the large intestine, where microbes chew them apart and use them for energy, through the process of fermentation. As a by-product, they produce gas."
A huge variety of healthy foods contain these complex carbs that we can't fully digest: virtually all beans, most vegetables and whole grains. For most people, this leads to an average of one litre of gas daily.
Kashyap continues: "When a complex carbohydrate reaches your colon, some bacteria will break it down first, and then some of their by-products will feed other bacteria. The whole community benefits from a single carbohydrate that you consume."
Beans, beans good for the heart
The rhyme about beans is true, they do make you fart and they are good for your heart… and your skin, brain, immune system, intestines and liver! This is partly because they contain oligosaccharides, as do onions, leeks, garlic and wholegrains and dark green leafy veg.
Sandwiched in between the simple sugars (monosaccharides) and the starches (polysaccharides), oligosaccharides are a group of carbohydrates that we hear much less about. They are chains of sugar molecules, usually two to ten in length, and comprising of at least some sugars other than glucose.
Flatulence is caused because we lack the digestive enzymes to break down the oligosaccharides and, instead, they are broken down by bacteria in the large intestine, which produce gas in the process.
But don’t ditch the beans! Oligosaccharides are essential for your health. They act as prebiotics to our good bacteria in our large intestine, feeding them. But why do we need trillions of mini mini-guys in our guts?
Beanz Meanz Good Bugz
No matter what you eat, you will have trillions of microbes in your intestines. It’s crucial that the species that protect you dominate over the ones that cause disease. Eating beans and other oligosaccharide foods, favours the ‘good’ bacteria because they feed them. Eating beans encourages the growth of bifidobacteria and lactobacilli which use the oligosaccharides to make short-chain fatty acids (SCFAs). SCFAs have an extraordinarily wide range of health benefits, for example they:
- Protect cells in the colon from damage, including against colon cancer and ulcerative colitis
- Improve immune system function
- Lower cholesterol
- Lower triglycerides
- Improve insulin sensitivity and glucose metabolism, helping to prevent and fight diabetes type 2
Bifidobacteria and lactobacilli also:
- Prevent the overgrowth of ‘bad’ bacteria and fungi
- Alleviate dermatitis in children
- Improve constipation
- Ameliorate diarrhoea, especially when it is caused by intestinal infections
- Synthesise certain B vitamins, including B9
- Synthesise vitamin K
- Promote further absorption of some minerals that have escaped the small intestine, including calcium and magnesium.
As different oligosaccharides produce different SCFAs – it is vital to eat a variety of peas, beans and lentils as well as cruciferous veg and the onion family in your diet.
Beans of all forms are particularly high in the oligosaccharide, raffinose which bacteria thrive on and produce large amounts of gas when breaking it down. You can reduce the amount of raffinose in dried beans by soaking them overnight in a large bowl of water and draining them before you cook them in fresh water.
Or you can buy (eg from Amazon USA) BeanZyme – a vegan pill that digests complex carbohydrates into shorter, simpler carbs that are much easier to digest. As a result, they get broken down in your small intestine, rather than making it all the way to the large intestine, where bacteria would ferment them, producing gas. However, there's a drawback to habitually taking pills to prevent gas – you starve your good bacteria. For most people, actively trying to limit your gas production isn't necessary. Purna Kashyap says. "The knee-jerk reaction, for many people, is to stop eating things that produce gas. But complex carbs are nutrition for the bacteria in our gut. You don't want to starve them unless there's a good reason."
Additionally, he notes, many people who believe they suffer from excessive gas production actually just have trouble with the flow of that gas through their intestines, perhaps due to constipation which can be prevented by a good vegan diet. Or, they might make the same amount of gas but emit it more frequently, in smaller doses. In either case, Kashyap says, "by removing the good foods, you're not solving the problem and may in fact be harming yourself."
Genuinely excessive flatulence can be caused by swallowing more air than usual, eating too quickly or food that's difficult to digest. If it is recurring and accompanied by other symptoms such as bloating, it can also be related to an underlying health problem affecting the digestive system, such as constipation, lactose intolerance or irritable bowel syndrome (IBS), and you should see your GP. But for most of us farting is a great thing, a natural part of the digestion of essential foods. A by-product of feeding trillions of life forms who nestle inside us, toiling hard to keep us ship shape.