[♩INTRO].

We know from chemistry that there are hundreds of salts out there. They’re compounds made up of positive and negative ions, usually formed when an acid reacts with a base.

But when it comes to food, there’s really only one salt that gets us salivating over potato chips:. Sodium chloride, otherwise known as table salt. In fact, chemists have been trying to cook up a good salt substitute for decades, and it has proven downright impossible.

Nothing quite matches the flavor of the tried and true. So what makes sodium chloride so special? Well, the truth is scientists haven’t totally figured it out yet, mostly because this seemingly simple taste is actually the one we know the least about.

Still, we do know the basics, and it seems that the sodium and chloride ions that table salt gets broken down into on your wet tongue happen to be the perfect ions for a couple of our salt taste receptors. We haven’t identified which receptors recognize the anion, or negatively charged ion, in a salt. But generally speaking, we perceive smaller ions as saltier, which is great for table salt because chloride is relatively small.

So something like sodium acetate is far less salty because the acetate ion is much bigger, although it is sometimes used to give chips a salt-and-vinegar flavor. Since replacing chloride doesn’t really work, the other option would be to replace the positive ion, sodium. Now, one of the best studied receptors is the epithelial sodium channel, which, as you might guess, is specific to sodium.

These pores let sodium ions flow into cells, and in taste cells, the incoming sodium ultimately sends a signal to the brain. The channel’s selectivity for sodium is one reason why the best salt substitute out there, potassium chloride, still isn’t very good. The potassium ion can’t pass through the channel to tell your brain, "Hello, infusion of salty flavor!" And that salt also gives off weird, bitter metallic flavors that are hard to miss.

Our tongues are so acutely sensitive to these that companies trying to lower the sodium content of their foods this way actually have to use a mix of regular salt and potassium salt so it’s less noticeable. Potassium chloride also isn’t safe for people with kidney disease, and can cause dangerous interactions with some drugs. So while it can work for some people, it’s not a perfect solution.

Now, there actually is a wonderful salt substitute, at least in terms of flavor. Lithium chloride tastes almost exactly the same because those epithelial sodium channels also let lithium slide in. But you don’t want to eat it, because it’s toxic.

Back in 1949, a company sold Westsal, a lithium chloride-based salt, as a nice alternative for people with high blood pressure or heart disease. But then doctors started seeing people with lithium poisoning, and a few people even died. Chemists are still working on more creative salt combinations that may one day more closely approximate table salt.

But until then, if you want more salty flavor, you’ll have to reach for good old sodium chloride. Thanks for asking, and thanks especially to our President of Space today: SR Foxley! Thanks, SR, for your support.

And if you want to get some perks or just show your support for the channel and help us keep doing what we’re doing, you can head over to patreon.com/scishow. [♩OUTRO].