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Why Do Beans Make You Fart?

Baked beans image via Shutterstock

Beans, beans, the musical fruit. The more you eat, the more you toot. But don't blame your flatulence on the poor legumes directly. The blame lies instead with the loads of little critters teeming in your gut.

Once you mash a bowl of barbecue baked beans into a fine mush in your mouth and stomach, it moves along to the small intestine. This organ is basically a molecular chop shop, where digestive enzymes strip your meal down for whatever bits and pieces your body can use and break them into smaller components that are more easily absorbed. Proteins get broken down into peptides and amino acids, fats into fatty acids and glycerol, and some carbohydrates into simple sugars. These are then absorbed through the intestinal wall to become fuel for your body.

This process isn’t so smooth with beans.

Their natural sweetness comes from a group of sugars called oligosaccharides (some of the more common ones in beans are raffinose and stachyose, which sound like rejected Musketeers). These sugars are hulking, awkward molecules. They’re far too big to slip though the intestinal wall on their own, and our guts’ enzymatic tool kit doesn’t have the right stuff to break the big things apart into more manageable pieces. So the sugars get a free ride though the small intestine. No one messes with them, and they move on into the large intestine intact.

Here their journey comes to a halt when they’re greeted by some of your closest friends, the 700+ species of bacteria that call your lower gut home. Fully capable of handling the big meal and never ashamed to have at your leftovers, the bacteria dig into the sugars. As they eat, their metabolic activity produces gases, hydrogen and methane among them. All that gas accumulates and eventually escapes your body as a fart, which may or may not be blamed on the dog.

Not all organisms have this problem with oligosaccharides, and some fungus species possess the right enzymes to break them down. These enzymes are easy enough to extract, and are often turned into gas-relieving supplements. Beano, the most well-known example, is made with the enzyme alpha galactosidase, derived from the fungus Aspergillus niger. Pop a tablet in your mouth before dinner, and the enzyme will snap those big sugars apart into handy little sugars like sucrose, glucose and fructose, giving you things your body can use and keeping you from giving a performance attributable to the musical fruit.

Today we're answering 20 big questions like this one. We'll plan more days like this, so if you have something you're dying to know, leave us a comment or tweet @mental_floss with the hashtag #bigquestions.

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Big Questions
Why Does Turkey Make You Tired?
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Why do people have such a hard time staying awake after Thanksgiving dinner? Most people blame tryptophan, but that's not really the main culprit. And what is tryptophan, anyway?

Tryptophan is an amino acid that the body uses in the processes of making vitamin B3 and serotonin, a neurotransmitter that helps regulate sleep. It can't be produced by our bodies, so we need to get it through our diet. From which foods, exactly? Turkey, of course, but also other meats, chocolate, bananas, mangoes, dairy products, eggs, chickpeas, peanuts, and a slew of other foods. Some of these foods, like cheddar cheese, have more tryptophan per gram than turkey. Tryptophan doesn't have much of an impact unless it's taken on an empty stomach and in an amount larger than what we're getting from our drumstick. So why does turkey get the rap as a one-way ticket to a nap?

The urge to snooze is more the fault of the average Thanksgiving meal and all the food and booze that go with it. Here are a few things that play into the nap factor:

Fats: That turkey skin is delicious, but fats take a lot of energy to digest, so the body redirects blood to the digestive system. Reduced blood flow in the rest of the body means reduced energy.

Alcohol: What Homer Simpson called the cause of—and solution to—all of life's problems is also a central nervous system depressant.

Overeating: Same deal as fats. It takes a lot of energy to digest a big feast (the average Thanksgiving meal contains 3000 calories and 229 grams of fat), so blood is sent to the digestive process system, leaving the brain a little tired.

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How Are Balloons Chosen for the Macy's Thanksgiving Day Parade?
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The balloons for this year's Macy’s Thanksgiving Day Parade range from the classics like Charlie Brown to more modern characters who have debuted in the past few years, including The Elf On The Shelf. New to the parade this year are Olaf from Disney's Frozen and Chase from Paw Patrol. But how does the retail giant choose which characters will appear in the lineup?

Balloon characters are chosen in different ways. For example, in 2011, Macy’s requested B. Boy after parade organizers saw the Tim Burton retrospective at the Museum of Modern Art. (The company had been adding a series of art balloons to the parade lineup since 2005, which it called the Blue Sky Gallery.) When it comes to commercial balloons, though, it appears to be all about the Benjamins.

First-time balloons cost at least $190,000—this covers admission into the parade and the cost of balloon construction. After the initial year, companies can expect to pay Macy’s about $90,000 to get a character into the parade lineup. If you consider that the balloons are out for only an hour or so, that’s about $1500 a minute.

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