In our recent analysis which looked at the causes of protein farts, we briefly mentioned a common ingredient used in protein shakes – bananas – and the best way to use them in order to minimize bloating.

In response to that, we received an email from a reader wanting more specifics about this fruit. He wanted to know if bananas make you poop? In his opinion they do and for that reason he avoids them.

The answer to this question is not black and white. As it turns out, how you eat them can determine whether they cause you to defecate or be blocked up. Here’s why…

The 2 types of fiber

oatmeal with milkCellulose – more commonly known as fiber – is not found in meats, fish, dairy, eggs, or any other food from animals. It’s only found in plant sources and there are two types:

  • Soluble fiber – This type dissolves in water. It acts as a sponge, soaking up moisture. A good example of this is oatmeal.
  • Insoluble fiber – As the name implies, this is the opposite… it doesn’t dissolve in water. Most of the fiber in carrots is insoluble.

Can your stomach’s hydrochloric acid (HCl), potassium chloride (KCl), and sodium chloride (NaCl) really breakdown and dissolve some types of metal like aluminum foil? Yep (1). However your stomach acid can’t break down fiber.

Neither can the intestinal bacteria do much to it. Cows have enzymes that can, but humans do not (2). From the fermentation that occurs, our friendly bacteria do benefit from the fiber, as it allows them to produce short-chain fatty acids and other metabolites. However they’re not digesting the actual fiber itself. It passes through your digestive tract and out the other side.

That’s why you can eat a salad the size of your head and it can have almost no calories, assuming you leave off the fatty dressing, cheese, croutons, seeds, etc.

What type of fiber do bananas and plantains have? Both soluble and insoluble. Most ingredient labels don’t break down how much fiber there is for each type in a food, instead they just list “dietary fiber” which takes into account the combined total of both types.

When you look up bananas in the USDA National Nutrient Database – which lists things far beyond the standard nutrition facts – you still aren’t provided an answer as to how much soluble vs. insoluble content there is (3).

How ripeness affects your bowel movement

Your average medium sized banana contains about 3 grams of total dietary fiber. Out of that, about 35% is how much that’s in the soluble form. Plantains have a similar ratio but more, simply because they are larger.

For your average banana, this translates to:

  • 1 gram of soluble fiber
  • 2 grams of insoluble fiber

With 2/3 of it being insoluble, it means that yes – it does add to the bulk of your stool, and yes – it does cause your food to move faster through your body. So do bananas make you poop more? If you’re sensitive and eat enough of them – or even just 1 in combination with other sources – it is true you might need to go #2. Having to poop more than normal frequency or more than once a day is definitely a possible outcome. That shouldn’t mean diarrhea though.

Do bananas cause you to retain belly fat? No, that one is a myth.

no green bananasYour bowel side effects might be determined by ripeness.  A green banana won’t have more insoluble fiber, but it will have something which is often considered a 3rd type of fiber – resistant starch. Technically it’s not fiber because your gut flora will eventually digest it, but it is resistant to digestion and hence the name.

Green bananas will have more resistant starch than a ripe yellow. If it’s really green, up to 50% of its weight (30 grams) will be made up of resistant starch. Something between a green and yellow banana will have 10 grams. Fully ripe or even overripe will have much less – as most of the resistant starch will have been converted to simpler sugars (4) (5).

Resistant starch acts like fiber and has properties of both types. That means it can increase the bulk of feces as well as make it move faster. Which occurs depends on your body’s unique biology as one factor, the other is one you can actually decide and control (see below).

Translation? The less ripe a banana is, the more likely it is to cause digestive side effects.

Constipation or defecation? You decide

You may actually be able to decide the outcome  of how bananas will affect you.

metamucil nutrition facts label

1 banana contains about half as much soluble fiber as 1 tablespoon of Metamucil

You won’t find it in chemical laxatives like MiraLAX or Ex-lax, but psyllium husk is a popular herbal remedy. It’s also the active ingredient in Metamucil. Each dose of Metamucil powder contains 2.4 grams of soluble fiber.

Metamucil is meant to keep your regular – healthy, normal bowel movements.

If a banana contains almost half as much soluble fiber as Metamucil, it too can help keep you regular. But remember, Metamucil is taken dissolved in a big glass of water. Guess what happens when you consume too much soluble fiber without enough water? Constipation.

This is because the soluble needs water (think oatmeal) and if it doesn’t have enough, it will remain dense. That can really slow down your plumbing.

So not only do bananas cause constipation potentially, but also loose stools is a possible outcome if you consume too much soluble fiber in combination with water. Healthy amounts of fiber in moderation will just cause “regular” poop, but in excess it may cause you to go more often.

scary carved bananaAnd in excess without water, it may just block you up.

Ultimately, the outcome may be determined by how much liquid you are consuming.

A banana in an acai bowl or smoothie is probably a good balanced ratio of water. A banana on its own, without drinking anything with it, is more likely to cause constipation.

Contrary to what you may believe, bananas don’t have excessive fiber content versus other fruits. A medium apple with skin also contains 1 gram of soluble fiber, but even more insoluble at 2.7 grams. A medium orange has 1.8 grams of soluble and 1.3 grams of insoluble. Most typical fruits have around this amount, with the exception of things like watermelon, cantaloupe, and other low cellulose types.

Something they do have excess amounts of is radiation. Yes, you read that correctly. This plant has an affinity for sucking up potassium-40 from the soil, which makes bananas radioactive.

The takeaways?

Don’t eat green bananas if you experience side effects from them.

Yes, insoluble fiber from bananas – as well as any other food – does increase the bulk of stools. This is because it is not digested by your body.

Yes, bananas can cause you to be blocked up if you eat them without enough water.

Yes, feeling the urge to poop is another outcome, if you consume too many bananas or even just one in combination with other rich sources of fiber.