Why do some farts smell so bad while others have no smell at all?

Flatulence, also called breaking wind, passing gas, tooting or farting, is a biological process that helps to release gas from your body. It usually comes out of the anus as flatulence or the mouth as a burp. Some intestinal gas comes from the air that people swallow when they are eating, chewing gum, drinking through a straw or smoking. Intestinal gas is also produced within the body when bacteria in the colon break down food. This is called endogenous gas. It consists mainly of oxygen, carbon dioxide, hydrogen and methane. It can also contain small amounts of other gases, such as hydrogen sulfide, which makes gas smell bad. Undigested carbohydrates are a common cause of gas, as the stomach and the small intestine cannot break these foods down. Instead, they move into the large intestine where bacteria begin to break them down, releasing intestinal gas in the process.

While passing gas is not something usually discussed openly, it is something EVERYONE does. In fact, the average person produces 500 to 1,500 ml of gas per day and expel it about 12-25 times. (even beautiful runway models fart!). Research has shown that there is no significant difference in the amount of gas that males and females pass. Another interesting fact is that people pass more gas when they are asleep. So, there is no need to ever feel ashamed of this very natural bodily process, even when it is smelly. 

In some cases, farts are silent and odorless or even loud and odorless, but they can become uncomfortable when they are loud and foul smelling. Smelly gas is not uncommon and is often considered normal. Some foods and medicine can be the cause. However, there are some instances where stinky farts can be an indicator of an underlying infection, digestive issues or a disorder.

Here are some reasons you may experience foul smelling flatulence.

• Although high sulfur foods are an essential part of a healthy diet, eating a lot of them can lead to your farts smelling like rotten eggs. Cruciferous vegetables like broccoli, Brussel sprouts, cauliflower, cabbage, garlic, onions, legumes, cheddar cheese, dried fruits, nuts, beer and wine are often to blame. Also, animal proteins such as eggs, meat and fish are high in sulfur. If you like these foods and don’t mind a little bad smelling gas, then you should continue to enjoy them. As with most things, moderation is key.

• An estimated 30 – 50 million Americans are deficient in the lactose enzyme which is needed to digest lactose, the natural sugar found in dairy products such as milk and cheese. Lactose passes through the small intestine without being absorbed then down to the colon where trillions of bacteria “have a little party”. The effect is pungent gas. People can also be intolerant to other sugars including sucrose (table sugar) and fructose (found in fresh fruit, corn syrup and some processed foods).

• Beans, beans, the magical fruit… The more you eat the more you toot. Have you ever wondered if this old saying is actually true? Well, it is! Beans are a great source of protein, antioxidants, vitamins and minerals. But, beans also contain raffinose family oligosaccharides (RFO’s), a group of complex sugars that are at least partially responsible for the bloating and gas that can occur after a beany meal. Humans lack the enzyme needed to digest raffinose. Lentils, legumes and cruciferous veggies also contain RFO’s. One study found that soaking dried beans in water helps remove RFO’s without compromising the nutritional value. Also, taking an enzyme based digestive aid can help ease the symptoms.

• Watch out for sugar alcohols, such as sorbitol and xylitol, which can be found in diet drinks, sugar free candy and foods and some gum. These particular sweeteners cannot be fully absorbed by the body, so they travel to the colon where they can contribute to bad smelling and excessive gas. With the popularity of no and low carb diets we are seeing more and more products on grocery store shelves containing these ingredients. 

• Certain prescription drugs, vitamins and supplements can do a number on your gut, including making your farts foul smelling. The reason they cause smelly gas differs by drug and person to person. Iron supplements are known to cause gas and bloating. Supplements containing fiber and some diabetes medicines can also make you gassy. Treatment for this may involve changing your medicine or supplements, which should NEVER be done without talking to your doctor first.

• Gluten intolerance, or its more severe form, Celiac disease, can also cause smelly gas. Celiac disease is an autoimmune disease where there is an immune response to the protein gluten and leads to inflammation and injury in the intestine. You should always talk to your doctor and get testing done to determine if you may have any food allergies, sensitivities or disease. 

• Constipation is the build-up of stool in your intestine that is hard to expel. If you aren’t pooping regularly it can cause bacteria and odor to develop. This can result in not only putrid smelling, but painful gas.

• Sometimes people will develop a bacterial infection in their intestines. This can cause a higher volume of gas with a strong odor. You may also experience diarrhea and abdominal pain. To determine if you have an infection you should always visit your doctor for testing and proper treatment.

• A rare cause of stinky gas is colon cancer. When polyps or tumors develop in the digestive tract, it can cause a partial blockage which can result in gas build up and bloating. As always, you should check with your doctor for diagnosis. It is recommended, by Dr. Tajong and the American Cancer Society, that people have their first screening colonoscopy at the age of 45.

The good news is, stinky gas alone is usually nothing to worry about. It is a normal part of our bodily functions and is even necessary to dispose of the waste and gas we produce. However, if you have other irregular signs and symptoms you should get them checked out immediately. Any change of bowel habits or abdominal pain that doesn’t go away could be a sign of trouble. Talk to your doctor if you have fever, weight loss, blood in your stool, diarrhea, constipation, a history of inflammatory bowel disease or colon cancer or any other questions and concerns. 

Here are a few things you can do to help alleviate some of your smelly farts…

• Keep a food journal to determine which foods may be causing your smelly gas. Once you determine what it is, try reducing the amount of that food you eat if you so choose.

• Drink more water to help remove waste through the body more efficiently.

• Avoid carbonated drinks that can produce gas, including soda, beer, wine and sprakling water.

• Eat smaller portions at a slower pace to encourage healthy digestion and reduce gas production.

• Eat probiotic foods like yogurt to help restore healthy bacteria in our body. You can also try taking probiotic pills.

We are looking forward to your feedback! Next month we will be talking about bowel incontinence.