19. Potassium: An Undeserved Reputation

There’s no avoiding discussing the banana in this episode, even though it really doesn’t deserve its strong association with Element 19.

Featured above: Slickly produced “textbooks” sent to American students in the 1930s.

Show Notes

Whose Law: Tomatoes actually compete with bananas for the title of “most popular fruit” — and are a better source of potassium — but according to US Supreme Court Case Nix v. Hedden (1893), tomatoes are legally classified as a vegetable, and not a fruit.

Since We’re Being Technical: All right, so there is some banana production in the United States, but since it accounts for 0.01% of total world production, I feel confident rounding down to the nearest integer.

Incidentally, I approached it a little sideways in the episode, but while bananas provided a reason to get imperialistic in South America, the excuse in Hawaii was pineapples.

Secret Genius: One of the more notable sources of the “bananas will kill you” myth is Karl Pilkington:

It Ain’t Over: Chiquita is happy to keep peddling banana propaganda to this day. On their website, they attempt to claim that bananas are not fattening because they have “no fat, cholesterol, or sodium … and satisfy your sweet tooth.” No kidding, ya dummies, it’s the sugar that makes them fattening. Just one more example of why it’s important to get your facts from reliable sources.

You’ll probably want to look at the full version here: https://xkcd.com/radiation/

Three Mile Island Wasn’t A Big Deal: One beloved factoid that didn’t make it into the episode is that bananas are measurably radioactive. A certain amount of the potassium in a banana is potassium-40, an unstable isotope.

Though it’s of uncertain origin, some cheeky physicist coined the “Banana Equivalent Dose” to give the lay person a grasp on tiny doses of radiation.

Randall Munroe of xkcd took this to a new level a few years back, providing a sort of logarithmic chart describing the various doses of radiation you’re likely to be exposed to in various scenarios. (The point is, you’re highly, highly unlikely to ever wind up being poisoned by radiation.)

Hawaii’s Last Queen: I was surprised to find that there wasn’t really a good video about the American acquisition of Hawaii on YouTube. The best I found is the following video, though its pace is pretty slow.

That Changes Everything: Eventually, United Fruit Company’s name became too tarnished, what with all the murder and exploitation and whatnot. They changed their name to Chiquita, a name that means “little girl.” A little on the nose there, fellas.

Episode Script

Hello class, and welcome to fourth period. It’s hard to believe we’ve already covered three rows of the periodic table, but those were the easy ones. As the elements we explore become more massive, they find more space to tuck away electrons than the periods that came before. So in period four, we’ll meet an entirely new section of the periodic table: the transition metals, which includes some real celebrities, like titanium, copper, and iron.

But first, we’ll kick things off with potassium, an element whose similarity to its overhead neighbors really helps reinforce the periodicity of the periodic table.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re meeting our recommended daily intake of potassium.

We know the alkali metals pretty well by now, and potassium isn’t throwing any curve balls here. Just like lithium and sodium, it’s a soft, grey metal that will float on the surface of water before reacting violently with it. With one electron in its valence shell, like all the alkali metals, it would be weirder if it did anything different. Potassium was actually the first element discovered by electrolysis, by none other than Humphry Davy. And also, just like sodium, the same translator gave element 19 a new name in German: Kalium. So for all the same reasons we discussed eight episodes ago, potassium wound up with K as its symbol, a letter that doesn’t even occur in its name.

And when it comes to essential nutrients, potassium is at least as important as sodium. Our bodies are filled with tiny biological structures that pump sodium and potassium into areas where they can build up an electrical charge, which is then used, for example, to fire nerve signals.1 These sodium-potassium pumps are incredibly intricate mechanisms that ensure only the designated ions can make it through. Well… most of the time. If you’ve been referred here by Episode 81, this is exactly the mechanism that lethal element disrupts.

That’s a pretty important function! You need to eat around three and a half to five grams of it daily, which isn’t too hard to accomplish if you enjoy fruit and veg. Of course, some foods are more abundant in potassium than others. Particularly rich sources include dates, raisins, almonds, watermelon, avocados, beans, greens, potatoes, tomatoes, you name it! So make sure to include plenty of those in your diet if you don’t already.

Ah. Right. You were expecting bananas.

I didn’t just skip them because “everyone knows” there’s a lot of potassium in bananas. I skipped bananas because they’re actually not such a great source of element 19. Don’t get me wrong, there’s about 400 milligrams of potassium in every banana, and that’s not so bad. It’s just nothing special, either. Even a milkshake has more potassium than that.

So why the reputation? Well, bananas have enjoyed a PR campaign unlike any other fruit in the supermarket.

Consider that bananas are the most popular fruit not only in the United States, but in the world. Americans eat more bananas in a year than apples and oranges combined.2 That feels wrong on a cultural level, but even more on a practical one: Over a hundred varieties of apples are commercially grown in the US, along with over seven million tonnes of oranges every year. Do you know how many tonnes of bananas the US grows in a year?


The United States doesn’t have the right climate for growing bananas. When the Spanish first arrived in Florida, they tried growing them, but it just wasn’t warm enough.

Equatorial nations like Guatemala and Costa Rica are better suited to the task. Before bananas could make their way to every breakfast table in the world, two technologies needed to be developed: Refrigeration and vertically integrated supply chains.4

In other words, cold boats, and a shipping method that was cheap and organized enough to deliver the product before it spoiled.

That became a possibility in the latter half of the 19th century. So, alongside the Declaration of Independence, bananas made their grand debut on the American stage at the 1876 Centennial Exposition, the World’s Fair in Philadelphia. Wrapped in foil and sold for a dime apiece, the banana was edible evidence of a shrinking world.5

With the infrastructure in place and the American palette thus primed, there was a brand-new market entirely up for grabs. Andrew Preston and Minor Cooper Keith were the men who grabbed it. Together, they formed the Boston Fruit Company. It was such a successful venture that before the century was out, Preston would transform it into the United Fruit Company, which brought production, shipping, and marketing under one roof.

This powerhouse of economic efficiency — and its competitors like it — would soon make the banana the most popular fruit in the world, but that was a distinction that didn’t come cheaply. It required millions of dollars in aggressive advertising, including sending textbooks touting bananas’ great value as a health food to every student in America. (This seems to be the origin of the high-potassium myth.)6

There was a cost in human lives, as well. In the interest of keeping labor costs low, fruit companies took over entire governments in South America, often violently, which is where we get the term “Banana Republic.” Some of these coups were actively supported by the CIA and United States military. Meanwhile, the Dole Food Company instigated a violent overthrow of the sovereign nation of Hawaii, annexing it in the name of the United States, to ensure that they wouldn’t need to pay high tariffs when importing their product to the US. This is a fact that, curiously, is conspicuously missing from history textbooks in Hawaii public schools.7

With its investors so protected, the banana became the first success story of factory farming, and the fruit itself makes a pretty good mascot for industrialization.

That might seem like a strange notion. We see bananas as natural in a world of synthetic chemicals, as green in a world of dirty manufacturing, and maybe most importantly, as something healthful and wholesome in a grocery store full of processed temptations.

But the truth is, even beyond the finely tuned machinations it takes to ship the crop around the world, bananas themselves are basically a standardized product, like a cell phone, or an automobile.

They have to be. You can’t build a global empire on a product that changes in unpredictable ways every growing season. And the banana is a very consistent crop. It is consistent in its shape, easily plucked, consistent in the time it takes to ripen, and perhaps most importantly, consistent in its taste.

This is because every banana on Earth is a clone.

Bananas aren’t grown like most other plants, with the pollinating and the planting and the germinating and everything. Instead, a small shoot is cut off a mature banana plant and set down in a new plot to produce a new plant.

Note: Plant, not tree. In the most technical, irritating way, bananas do not grow on trees. The pseudostem of a banana plant is made of bunches of leaves pressed together, not wood. That means, botanically speaking, the banana plant is a perennial herb.8

A perennial herb with untold millions of genetically identical versions of itself spread across the Earth, ensuring that, no matter where they’re grown, customers can expect a product that’s sweet, and soft, and tastes nothing like it did a few decades ago.

The banana that was brought to Philadelphia in 1876, and made the fruit so popular in the first place, was a variety called the Gros Michele. But the problem with growing a single variety of a crop is that the entire population shares the same vulnerabilities, especially to disease. That problem is even worse when each plant is an identical twin.

In the mid-twentieth century, a fungus known as Panama Disease had practically driven the Gros Michele to extinction. The banana industry was in crisis. In desperation, fruit companies searched for any other variety of banana that might be resistant to the disease.

In a neglected corner of a Chinese greenhouse, the Duke of Devonshire found one: The Cavendish. Where other varieties of banana succumbed to Panama Disease, the Cavendish was resilient. It was the last, best hope for those corporations that depended entirely on bananas. And, as we saw in Hawaii and South America, those corporations were willing to go to pretty extreme lengths to protect their profits.

There was only one problem: The Cavendish didn’t taste that good. It had a much milder flavor, tasting almost chalky, and it was both smaller and more easily bruised than the Gros Michele. But what was United Fruit going to do? Stop selling bananas? So they held their breath to see if customers would bite.

We did! And if you’ve never had a Gros Michele banana, you might not even understand why there was such a fuss. The Gros Michele is very rare nowadays, but those lucky enough to try it commonly describe it as tasting “more banana-like.” For the rest of us, the closest we’ll get is artificial banana flavor, which is apparently modeled after the taste of the Gros Michele, not the Cavendish.

But that’s not the end of that story. For the past half-century, Panama Disease has been evolving. There’s now a strain that does infect Cavendish bananas. A few scientists are working on the problem, but strangely, the big fruit companies haven’t shown much interest in those solutions.

This probably won’t spell the end for the banana, but it could cause its already artificially low price to skyrocket — and perhaps dethrone it as the world’s most popular fruit.

Good thing, then, that we have such abundant supplies of potassium in our diets already. And contrary to what you may have heard, you will not die if you eat too many bananas, or spinach, or whatever.

It is theoretically possible, of course! Like Paracelsus said, “the dose makes the poison.” It just so happens, in this case, that the necessary dose would require you to eat approximately your body weight in bananas (or whatever).9

But there are more concentrated sources of potassium in the world. Animals of all kinds, from scorpions to snakes, use potassium chloride as a key ingredient in their venom.

That trick works because of potassium’s role in nerve signaling. By overloading cells with extra potassium, it sort of fries those circuits, and muscles can no longer move. Inject enough potassium, and one of those paralyzed muscles is the heart. Even if it’s not lethal, it’s likely to make for a very tender wound.

Potassium chloride is even part of the chemical cocktail that US prisons use to execute prisoners sentenced to death. It’s a fairly controversial inclusion, since it can literally burn the victim’s veins as it flows through them.10 I’ve actually written a little about the chemistry of capital punishment before. You can find that in the July 2, 2018 Element Update on episodic table dot com.

But for most of history, if potassium was going to kill you, it wasn’t going to be in the form of a poisonous injection. It was far more likely to be the propellant behind a lethal dose of lead.

Sometime well over a thousand years ago, Taoist monks in China were performing some experimentation. Nothing out of the ordinary for ancient alchemists, just searching for a little elixir of immortality.

One of the cocktails they came up with involved sulfur, charcoal, and saltpeter — AKA, potassium nitrate. This mixture of three powders delighted the monks with its ability to “fly and dance” when ignited.

It’s difficult to overstate the effect black powder had not only on warfare, but upon world history. Over several centuries, the technology made its way across Asia and Africa. Finally, it made its way to Europe, where artisans were familiar with casting enormous pieces of metal for use as church bells — and found that those same skills could be applied to create cannons and guns.

Europeans improved gunpowder technology to the point that, when they brought it with them across the Atlantic, they were unstoppable.

But they were not invincible. While those Taoist monks had made one of the most influential discoveries in human history, gunpowder is about as far as you can get from a potion of immortality.

Don’t go looking for a box of bullets, element collectors, because modern-day ammunition is actually an even worse source of potassium than a banana. Saltpeter-based gunpowders went out of fashion around the 19th and 20th centuries, when scientists discovered new, smokeless propellants. Sadly for us, “smokeless” means “potassiumless,” too.

As an essential mineral for all life, potassium is another one of those elements that your garden wishes you would collect. It’s abundant in fertilizer, so it can be abundant in our food.

You could also sprinkle it on top of your food, for taste, if you so desire. But you probably don’t. Potassium salts are sold as an alternative for those who’ve been told to keep their sodium intake low, but they do impart a distinct metallic taste.11

From some compound like its salts, it is possible to isolate metallic potassium. The process would be pretty similar to the one used to isolate sodium. If you’re one of the listeners who performed that home chemistry experiment, I hope you’ve recovered.

However, if you prioritize presentation over purity, there is a pretty curious way you could showcase Element 19 alongside its cousin, Element 11. When potassium is alloyed with sodium, the resulting metal is a liquid. This is actually a common phenomenon in chemistry: Mixtures tend to have lower melting points than their constituent elements. This is just a particularly odd case of that.

What doesn’t change is those metals’ propensity to spontaneously combust upon contact with water or air. But if you’ve made it this far in the series, I’m sure you’ve already come up with a solution for something as trivial as explosions.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. Special thanks this week to Consulting Producer Derrick Burton for his help tracking down some early banana propaganda. If you’d like to learn an incredible amount about bananas that I had to cut from this episode, visit episodic table dot com slash K.

Next time, we’ll continue our war on breakfast with calcium.

This is T. R. Appleton, reminding you, while we’re dispelling food myths, that spinach isn’t very high in iron, either.


  1. The Elements of Murder: A History of Poison, p. 376. John Emsley, 2006.
  2. The New York Times, Yes, We Will Have No Bananas. Dan Koeppel, June 18, 2008.
  3. University of Florida, Banana Market. Edward Evans and Fredy Ballen.
  4. The World Banana Economy, Pedro Arias et al.
  5. National Geographic, Why Are Bananas So Cheap? Daniel Stone, August 10, 2016.
  6. A Study Of The Banana: Its Every-Day Use And Food Value (Student’s Manual). United Fruit Company, 1939.
  7. Vox, The Improbable Rise Of The Banana, America’s Most Popular Fruit. Joseph Stromberg, March 29, 2016.
  8. University of Arizona Campus Arboretum, Musa acuminata.
  9. Snopes, Will Eating Too Many Bananas Kill You?
  10. PubMed, Chemical Burn Caused By Dermal Injection Of Potassium Chloride. Park SM, Sohn YD, Ahn JY, June 2011.
  11. Something of a consensus, but just as a for-example, this Quora post.

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