Salt-tolerant plants, astronaut pee, & the evolution of blood

Eleanor Konik

Eleanor Konik

Professionally, I teach world history. In my downtime, I enjoy combining storytelling with my love of sharing obscure history and science.


I was looking into salt-tolerant plants for a piece of flash fiction I'm working on. It involves a conservationist trying to keep an invasive, man-eating species out of a local swamp. I wanted to know more about salt to really round out the worldbuilding. So I started digging into stuff like wars over salt, salt-tolerant plants, how animals handle salt...

Quick Facts

Space Pee

Scientists studying salt intake & urine in astronauts recently discovered that although increasing salt in the diet can lead to more urine output, this isn't actually linked to liquid intake; a high salt diet causes the body to break down fat and muscle, releasing water, similar to how camels survive in low-water environments. The process requires energy and often leads animals to eat more food (or lose weight, but this is a dangerous way to lose weight on purpose).

Fish Excretion

Freshwater fish have "physiological mechanisms" that concentrate salt in their bodies. Saltwater fish excrete unneeded salt thanks to their kidneys & chloride cells in their gills, which produce a particular enzyme. Fish that live in brackish environments can do both. Fish that can only handle one level of salinity are called "stenohaline" species, while more adaptable species are considered "euryhaline."

Cooking Salts

Salting foods like meat and vegetables tenderizes them because osmosis basically makes them excrete water. Sometimes, as with tomatoes and cucumbers in a salad, this is the opposite of what you want. It's really hard to taste the difference between different types of salt; the main differences have to do with the shape of the grains. Kosher salt doesn't have additives (like iodine or anti-caking chemicals) and is flakier, which makes it easier to pick up. Sea salt is mostly useful as a garnish, and colored salts tend to have more "natural" minerals, but all brands and types of salt have slightly different levels of "saltiness," which can make cooking with them tricky.

Iodine Ash

One of the oldest non-nomadic tribes in India, the Apatani, live in an isolated area with no access to saltwater or salt deposits. Instead, they eat tapyo, which is a bitter, filtered ash made from banana leaves, millet, and other local shrubs and bushes. It's a pain to make, but brings enough iodine into their diet to help avoid goiters and other health defects.

šŸ“— ICYMI: If you found this interesting, you may also enjoy my previous newsletter about clever ways the ancients made food last centuries: Food Preservation.

šŸ’š If you learned something from this overview, consider forwarding it to a friend and encouraging them to sign up for more research deep dives into obscure history and science.

šŸ“… What's the coolest factoid you've ever learned from me? Hit reply and let me know ā€” it really helps to know what you're interested in.


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