StarTalk Podcast
Hosted by Neil deGrasse Tyson
Original podcast
Before you add some extra flavoring to your food, sample our show on the health effects of salt.
6,899 words · 3 speakers
Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.
Welcome back to StarTalk Radio. I'm your host Neil deGrasse Tyson. I'm an astrophysicist with the American Museum of Natural History in New York City, where I also serve as the Director of the Hayden Planetarium. My co-host this week is the one, the only Eugene Mirman.
Hello.
Hello, hello.
As you know, we're continuing our discussion on the science of salt begun in the previous hour.
So lucky you found a salt comedian.
It was tough in the Yellow Pages, you know.
I know a lot about salt.
Previously, in that previous hour, we discussed how salt has flavored human culture and human history.
We did, yeah. We didn't phrase it that way luckily, but yeah.
And in this show, I want to focus differently on salt and find out what role it plays in our human biology, just in life in general, not so much culture, although that culture discussion was, I mean, I learned a lot.
Yeah, I didn't know all that stuff.
Yeah, yeah, that's good.
I mean, I figured, but now I know for sure.
And so we can ask the general question, you know, why do we love salt so much? You know, so many people just love salty snacks and they even prefer that over sweets. Actually, some they combine them, right? They have like the sweet-covered salty pretzel.
Exactly. Salt is the original heroin.
Not heroin as the female hero, but...
No heroin, the drug that makes you write great songs.
And so you wonder, is there some biological reason for preferring salty snacks? I mean, this is a, this is an important question. Just to remind everyone, salt, table salt, sodium and chloride, each of them rather deadly on their own.
What about, isn't there salt that's iodine, iodinated?
Oh, oh, sorry. So what happens is iodine is a, is an important nutrient in the body. And, and back when we were trying to figure out how to keep the country healthy, most of that happened just before, but mostly after the Depression, people found ways to link certain nutrients to different foods that are common. Right, and so you can iodize salt and not would not have it affect the flavor in any fundamental way and still get iodine into the body. And vitamin D dissolves well in fat, so in in milk fat, so you add vitamin D to the milk. You don't put vitamin D in the salt, right?
Right.
So you divide it all up and we have vitamins coming at us from every direction we turn.
Hmm.
And but salt, you know, salt seems to be everywhere.
Yeah.
So here's what happens, what you, once you eat salt, your body breaks it down into sodium and chloride ions.
Mm-hmm.
And ions are like, it's where there's a net charge in the in the atom.
And so that you can do interesting things when you have.
You could turn it into like a party inside your body.
Well, it makes it a little more reactive. I mean, it's it's it's when when you have ions floating around floating around your body. And so sodium ions are are like really important for maintaining your blood pressure. And this is this issue with salt and your blood pressure that we always hear about. There's an intimate relation between the two. So for example, if your blood pressure goes down, just take this as an example, blood pressure goes down, then hormones in your body tell the kidneys to retain sodium. And when you retain sodium, that leads for you to retain water, which increases the volume and the pressure of your blood, bringing the blood pressure back up.
Would you also be able to just eat a little salt? Would that have a similar effect or no?
Uh, well, well, that's that, so both of those work in the same way.
Because now you have the extra, so so instead of it retaining the the the sodium and then forcing the increase in the water retention, you get the sodium for free, right?
Right, so blood pressure is just all about having a perfect amount of salt.
Uh, in the end, yeah.
And running and doing a lot of.
And eating healthy, right, right?
Well, eating healthy, but in but with some salt.
And sodium ions play a role in muscle contraction and and the firing of your nerves. That's all, that's your electrical system. And in your electrical, I think it was the electrical system.
Sure, of the body?
Of the body, right. You have your plumbing, that's your like your intestines.
Okay.
You got your carpentry.
And that's what, like your fingertips?
No, that's your bones.
Okay. You, okay.
Right, you're plumbing, your carpentry, and you got your electrical.
And you got your electrical.
Right, right.
And then the roof.
So sodium ions, so they play a role there where it's important for controlling the pressure inside of your body's cells.
And what happens if the pressure gets too high or too low, the cell wall can just explode and that would be bad.
Yes, it would be terrible if you had so little salt you exploded or so much salt you exploded. Either one sounds bad.
And the chloride ions, those are great. Those are used for digestion. You know, you know what the acid in your stomach is that digests with? It's hydrochloric acid.
Is it really?
It's gotta get the chlorine from somewhere.
So you can eat through a table?
It could at the right concentration, right. And it's been a mystery over all the years, why doesn't the hydrochloric acid dissolve your own stomach line?
Yes. That's something I would like to ask you right now.
I don't have an answer for that.
Oh, oh. We're all walking time bombs with melting stomachs.
So let's check out our clip. As we learned in the first hour, I had a long interview with Mark Kralinski, the author of Salt: A World History. Not only all the role that salt played in cultures and wars and love and deities, but also just the health of salt, the health considerations. And let's just pick up on that interview with Mark Kralinski, taken in my office at the Hayden Planetarium. Obviously, sweat is salty, tears are salty. So when you are low on salt, your body tends to crave salt.
If you lack salt in your body, biologically, your body will have this need for salt, but you won't crave salt in the same way that if you didn't have enough water, you would be thirsty, or if you didn't have enough food, you would be hungry. I became aware of this by interviewing World War II veterans in the Pacific, who got very sick, very bad headaches, and just were feeling weak and on the verge of collapse. And they went to doctors and the doctors said, well, it's a lack of salt, and they gave them salt tablets, and then they were better. To a person, the people I talked to were absolutely amazed by this because they had experienced no desire to eat salt. So this is a Kralinski theory with no scientific backing whatsoever.
But, you know, we really like salt, and almost anybody left to their own devices will eat much more salt than you need to survive. I think the reason for that is we have this built-in desire for salt because our system doesn't tell us, it doesn't warn us of a shortage, so it makes sure that we're just always getting enough.
That's the Kralinski theory.
So do you know a full grown adult contains about 250 grams of salt, which would fill about three to four salt shakers, just in case you were wondering?
I did not. I was both wondering and didn't know that offhand.
I know.
But I now can't wait to go and tell people that myself.
You were burning to know this. And the only question about drinking seawater, you know why we can't drink seawater?
Why not?
Because seawater is four times saltier than your blood. That's bad. And so if you were thirsty and you decided to drink seawater, your kidneys would use up the water trying to flush out the extra salt. So then it's actually just counterproductive. You'd actually die from thirst faster if you drank seawater. Crazy. We're done with this segment. But StarTalk returns, more about all the ways salt can season your health.
This is StarTalk Radio. I'm Neil deGrasse Tyson, here in studio with my co-host this week, Eugene Mirman. Eugene, thanks for joining me again.
You're very welcome.
And you tweet at Eugene Mirman.
I do.
M-I-R-M-A-N.
Exactly.
And I follow you.
Yes.
I don't know if you follow me too?
Of course. That's what I know about science.
So, yeah, because you don't have to. It's not a prerequisite for being my co-host here, just so you know.
Yes, no, I understand. I do it of my own free will.
I tweet at Neil Tyson if anybody's interested. They're just cosmic brain droppings, actually. So, topic for the show is salt and the flavor it adds to our lives, yes. And in a previous segment, we learned why salt is important for our health.
In an interview that I had in my office with Mark Kralinski, author of Salt: A World History. But the real question that plagues us all is, how much salt is too much salt?
This is what I don't know how much is.
Well, definitely a glass of seawater is too much, because it has four times as we learned the salt. That's great to know. I always wondered why you can't drink it.
Somebody's paying good attention to what's going on here.
Oh, yeah, I'm taking notes.
So, let's check on a clip with Mark Kralinski, find out how much salt is too much salt. That's been a raging debate among nutritionists and doctors and the people who just love their salty snacks. Let's check out, find out what he has to say.
At that basic cellular level, your body would not function without sodium and chloride.
So how much salt do we actually need?
Can I talk to a doctor on this one? I don't remember the exact amount, but we're talking about a very small amount. As I said, if you eat red meat, you get all the salt you need.
But I eat red meat and pretzels and popcorn and all these other salty things, so I'm totally...
You're way over. You could just eat the pretzels and popcorn. You don't need the meat. The more difficult question is how much salt is too much? Here's where you get into big debates because it's not the same answer for everybody. Our kidneys are designed to deal with excesses of sodium and chloride. And if everything is working the way it should be, you should be able to eat enormous excesses of salt without any consequence. And many people can, but some people can't.
So your point is, we should not think of too much salt as a general health problem. It's only a health problem for which it's too much salt.
Yeah, you know, the health community gets very angry with me about this because, you know, the problem with health officialdom is that they want there to be sweeping rules so that they can catch everybody. And they don't like it when people like me say that some people can eat excesses of salt with impunity because then, you know, everybody will say, "Oh, I'm one of those people." But some people can and some people can't. You get these comparisons. For example, when I get into this debate with health people, they start making comparisons to smoking. It's not the same thing as smoking. Any amount of smoking is bad for you. Any amount of salt isn't bad for you. A certain amount is bad for you.
And how much that amount is depends on the individual.
Limits here. So the the US, the Food and Drug Administration suggest an upper limit for salt intake of five, between five and six grams per day.
Mm hmm. And how much, what's that the equivalent of?
Well, what's and and they want you to take in less if you're known to have high blood pressure or some other health issue. So a gram is one thousandth of a kilogram?
Yes, no, that so far, but meaning like vaguely like when you see it on a table.
So we do it. So watch. So a kilogram is a little over two pounds, 2.2 pounds. Just call it two pounds.
Sure.
So a thousandth of two pounds is a 500th of a pound and an ounce is a 16th of a pound. So 600, this is a 30th of, one gram is a 30th of an ounce.
Approximately, just doing that off the top of my head. So a 30th of an ounce.
The same amount a teenager needs to get high to enjoy a concert.
I guess I don't know.
I'm just guessing.
And so, but the, but actual data from people's real food consumption tells us that the average American man consumes more than 10 grams of salt per day, almost twice as much as.
And that's in their coffee alone.
That's right. Well, so, so here's the problem. So of course, increased salt gives you, puts you at risk of high blood pressure and heart disease and stroke and, and some people are more salt sensitive than others and for reasons that aren't always well known, just the genetic spread of what people are in this world.
Is there a test to find out if you're one of the people who can eat unlimited salt without having no harm done to you?
That.
Is that a test anyone gives somebody?
What's funny is some tests, you know that they don't work for you because you died from it.
Yes, yes, I guess I'll eat a pound of salt later this evening and if I live, I know that I'm finding salt.
You are cool eating, eating salt. Now here's an interesting study. So last year in the New England Journal of Medicine, which you read every night before you go to sleep.
Yeah, I can't fall asleep without reading some, some horrifying medical information.
They reported that if people removed a half a teaspoon of salt from their diet. Okay. So that would be like about three grams for, per day, that it would prevent nearly 100,000 heart attacks each year.
And that's, you know, if what's weird is people freak out. Do you remember the alar scare with apples? There was like, might have been cancer from the alar on apples and people stopped eating apples.
And, and the, the risk that you would have experienced from that was really low, but that it was any risk at all, people reacted. And so here we have, we can prevent a hundred thousand heart attacks just by reducing it.
Right. Well, I think if apples were as fun as salt, then it wouldn't have been treated like that.
But here's the problem. It's hard to reduce that much salt from our diet because eighty percent of the salt we consume is already in the food when we buy it.
And the food that, put up the list, you know, who doesn't like potato chips? I love potato chips.
Yeah. Who doesn't like soups and cheeseburgers? I'm reading from your same list.
And no, the thing is with potato chips, I've tried the low salt potato chips. It's like, why am I wasting my time? I can't go.
Well, then you have to add other spices to cover for them being those.
Well, is that what that is with the barbecue flavor?
Maybe, I mean barbecue, I'm sure is very salty.
But just the vinegar flavor?
Maybe. I mean, probably any chips. Maybe chips is not the thing that you could use.
I'm just saying, I can't, you know, when I eat potato chips, I can't think of, you know, this needs vinegar. You know, it's just not a thought I ever have. I, I think there's nothing I've ever eaten where I said, this needs vinegar.
I don't know. Vinegar makes the soup dumplings delicious.
But, you know, pasta and there's a lot of, there's a lot of salt and cheese and of course soups.
Pizza.
You know, and.
So what you're saying is if you, if you make food for yourself, you'll be fine. And if you eat at a deli where you buy like pizza and chips.
I think so, the deli.
Left to live.
Yeah. Deli, it's, you know, deli should have like warning salts or, you know, it's salt.
I think that was a thing, wasn't it? I think that, that there was talk of there being like a salt warning or limits on salt.
Well, actually.
By the FDA, I believe.
In a way, given the previous hour that we discussed salt, delis are like the holdout from another era. Where you preserve the meats with salt and smoke and all these other ways. And so the deli is kinda, and we, we, especially particularly in the, in the, in the, in the big cities, New York and LA.
There's this, you know, you walk by a deli, you gotta, you gotta slow down and maybe step in there. Right, you know.
And get some salted cold cuts.
And then the deli goes in.
And try and see if you can't kill yourself with them.
And they go in for the kill with those huge sweet desserts.
Because if the salt wasn't good enough to kill you, the dessert will get you. You know, in other cultures, there's not a habit of adding salt.
Though they have food in other cultures. America's the last country left that still has food. And we make it all salty to try to destroy ourselves.
But think of in China and other Asian cultures, that you know, there's soy sauce. It's in the sauces. It's not, there's no salt shaker on the table typically in a Chinese restaurant. And.
That's big, yeah, but Chinese food's problem is not lack of salt.
Deliciously salty.
And you know, it's fun, I was fun, I was great to learn that in a, in a, in a jar, not jar, a bottle of Worcestershire sauce.
Mm hmm.
You know, the active ingredient in the flavor is an anchovy.
Oh, really?
It's a dissolved anchovy.
It sounds delicious.
Well, they.
No wonder I like it.
And so, you know, it's, it's, one of why you don't like it or.
No, I love it.
Yeah, yeah, it's great, it's great, and I.
And I love anchovies, they're so salty. Are they naturally salty? It's probably a little salt added, huh?
Well, I think they are from salt water, so you get some salt for free.
Oh, good.
But, but, right, and, and, and, so, so it's a, when, when, when you're taking the salt separately. So what you can do is you can say, since so much salt is coming from my diet, I will remove salt shakers from my table.
That would be a very good way to do, to have some force on what, on what you're, what, on avoiding the heart attack that the studies show.
Right, right, just don't have a salt shaker, who, but who adds like salt to their pizza? Like, who does that?
Right, yeah, this pepperoni is not salty enough. You gotta, you know, you gotta, you gotta do this. And, by the way, so, of course, modern salt, we mentioned earlier, has some additives.
Uh, there's the, the, the pouring, uh, I don't know what they use for that. It's, it's an ingredient that they put in so the salt will continue to pour. Because salt loves water and it loves caking, and so.
That's why some salt shakers are full of rice also.
Yes, exactly, the rice absorbs that, and that was the Morton salt, uh, uh, motto, when it rains, it pours. Is that clever?
Yes. Now I understand.
Yeah, you didn't understand that your whole life.
Yeah, exactly. Because I didn't grow up figuring out why salt was messed up in the 50s.
And so there's those additives, and of course, they add iodine to, um, it also prevents goiter.
Uh huh. Oh, good. Wait, uh, I think we have to wrap up last.
Yeah, we'll wrap up now, but we have another segment coming, more about salt, more of my interview with Mark Kralansky, author of Salt: A World History, and we'll be back in the StarTalk Studios. Willie Brass Tyson here with Eugene Mirman.
Welcome back to StarTalk Radio. This is Willie Brass Tyson, your astrophysicist host. With me this week is Eugene Mirman. Eugene.
Hello, Neil.
And our tasty topic this week is on salt.
And the science behind it. Now, now, you're an expert on salt because you're one of the voices in Bob's Burgers.
Yes, which is a salt-based cartoon. Yeah.
Animated feature on Fox?
And, and, and it's some, it's before or after The Simpsons and Family Guy? How do I find it?
It's, it's after The Simpsons and before Family Guy. They luckily don't air three shows at once and space them out.
Simultaneously?
Yeah, so it's, it's 8:30, 8:30 on Fox.
Uh, Eastern Pacific, right?
Yeah, yeah.
The Central.
And Central's 7:30.
Exactly. No one cares about Mountain Time, right?
No, but they, they know. But when they hear me say this, they're like, ugh, he's skipping Mountain Time.
It's, you know, more people live in the metropolitan area of New York than in the entire Mountain Time Zone.
See?
Yeah, that's why.
That's why I don't even bring it up. Unless my hand is forced.
So Bob's Burgers, that makes you an expert on salt.
I cannot rely entirely on that. I have my interview clips from Mark Kralansky, who wrote Salt: A World History.
It's a wise choice to spread out the experts.
So, you know, as we know, we have a basic need for salt.
Interesting study, our researchers found that the biological hardwiring in our brain for salt follows the same pathways and nerve cells as some addictive drugs.
So...
It really is the original heroin.
That's right.
I think it actually, or MSG follows the same pathway.
Something where you gotta come back and have it and need more of it and even more, and you reach a new plateau of it and then you gotta put more on it, right? I mean...
Oh, just like an actual drug.
That's what I'm saying.
Where you're like, this is not working anymore. I need a whole bottle of salt and a bottle of whiskey.
And it's interesting, we complain, we complain about salt consumption today, but it used to be much higher.
Right, but that's because they had no other way. Yeah, but people died at 41.
I know, I know. Well, so I asked...
Because they were so salty.
I asked Mark Kowalski about this, just to get some insights.
Good.
Into the decrease in our salt consumption. Let's see what he tells us.
Data shows that salt consumption is down 50% per capita from a couple of hundred years ago. Is that entirely because we're not eating preserved foods in the way we once did?
We eat much less salt than we used to because we don't live on a diet of salted food. For instance, you know, in northern countries in the wintertime, almost everything you ate was salted, and also salted, much more salted than it is now. So, in prior centuries, people ate enormous, enormous quantities of salt. And I'd love to know, there doesn't seem to be any way of researching this, what the comparison is on blood pressure, whether people in earlier times had higher blood pressure.
I don't know. And with higher blood pressure, there would have been more strokes.
And strokes would have been more severe, and so...
And heart problems.
And you go to an old cemetery, half the cemetery, people died, you know, between 50 and 60 or earlier, so it makes you wonder.
Yeah, yes, but that's also a reflection on our improved ability to treat diseases, not necessarily that we're healthier.
But you could ask the question, if we upped salt consumption today, given what we know about excess salt, to the levels of 200 years ago, that would be a fascinating experiment to at least do on paper, what consequences, how many people would die, more people would die each year? That's gotta be a doable thought experiment.
Yeah, if you upped people's salt, but then you had better treatment for high blood pressure and heart attacks and strokes, would it all level out? The fact that we're even discussing this, I should tell you, means that we have brought on the fury of the American Medical Association, which doesn't seem to think that people should be guinea pigs. I don't know. That's their hangup.
I do really like the idea of a salt town where 1,000 people's intake of salt goes sky high, and we see if they die or not over a period of decades.
It's funny that the guinea pig as a metaphor, it doesn't think people should be guinea pigs, right? Because they're people.
Right. We should maybe first give salt to guinea pigs.
See how their blood pressure is, and then try it on kids. On human children.
So, I don't know if you knew that the United States is the largest producer and consumer of salt in the world. We produce 40 million tons each year.
I have a feeling that we are the largest producer and consumer of a lot of things.
It's true.
Even probably turmeric.
And that's a billion dot billion dollars' worth of salt. And guess what? Only 8% of that is used for food.
What's the rest of it used for?
Well, half of it is used for de-icing roads.
How do you like that? You've driven by these big salt repositories in municipal centers where they just back up the dump trucks and load up.
Get a lot of salt.
Load up the salt. And, of course, it's had a bad environmental impact. The plants along the side of the road are sort of susceptible to salt.
Salty. Are too salty.
The industry claims 14,000 uses of salt.
Name 2,000. I mean, I believe you, but just name just 2,000 of them.
So, some people still put salt in the water to raise the boiling temperature so you can cook foods a little faster. That's a good one. Also, I do this. I put in a dash of salt while you're boiling vegetables, and it keeps the color of your broccoli bright and green.
I did not know that.
Rather than that faded green you get in canned broccoli. Yeah, yeah. And you also use it, I would do this, it helps make ice cream freeze.
The salt is not in the ice cream, but in the surrounding bath.
And here's something you might not have known. You use the salt because it melts the ice at the temperature of the ice. And liquid at that temperature absorbs heat faster than solid chunks do in contact with the ice cream canister. What do you think of that?
I think you're lying. No, I think that's neat.
More when StarTalk continues, I'll tell you how I make my ice cream. On a StarTalk show devoted entirely to salts. We'll see you in a moment.
Welcome back to StarTalk. I'm Elyse Grant Tyson here in studio with my host this week, Eugene Mirman.
And we are talking about salt and the way it flavors our lives. I was going through a list of the salt industry's claim of 14,000 uses of salt. And you asked me to name 2,000 and I'm prepared to do that now.
Great.
Other than, of course, removing rust and making soap go.
Well, okay. But I wanted to continue. The ice cream thing is important because there's important thermodynamics that goes on in ice cream.
If you have the ice cream batter, I mean, the mixture in the canister and you start churning it. If it's just simply ice that's around the canister, edges of the ice touch the canister and the heat isn't pulled out of the mixture very, very efficiently. You can plunge your hand into a pile of ice. It's cold, but you're not, you're okay with it.
But salty ice.
If you melt the ice with salt, you are not raising the temperature of the ice. The ice becomes liquid at the same temperature it used to be as ice.
At 32 degrees?
Well, no, even colder. It's just colder ice. It'll melt the ice at 25 degrees. You melt it, now you have water at 25 degrees and water will suck that heat out like it's nobody's business.
Oh, wow.
That's why you'll freeze much faster in water than in any other bath you could put yourself in.
That's why it's terrible to fall into the ocean off a boat.
Off of the Titanic, yes.
That's just one boat, but I bet any boat, even a small boat, it would be terrible.
Yeah. Even small boats.
Well, in my interview with Mark Kralansky, who wrote Salt, A World History, he actually has recipes for food in his book. I had to ask him about it. I said, where's he going with this? Let's find out.
I think that recipes are great archival material. And it kind of gets misunderstood, you know, this isn't a cookbook. I'm not saying that if you cook this recipe, you'll have a great dish. Many of the recipes I don't even try. I'm interested in the ingredients they use, often the way things are talked about. You can find a lot of interesting things in old recipes. When I did my cod book, I almost put a disclaimer there, you know, don't try this at home, folks. And when the book came out in Icelandic, I went to Reykjavik and they did this big dinner in my honor. And to my absolute horror, they prepared all these dishes that were recipes from my cod book.
What a horrendous meal that was. Serves me right, I guess.
Is there any recipe from your salt book that you have tested and you would recommend for the listener?
Oh, yeah. Some of the Chinese recipes, which I got from Chinese chefs in Sichuan province, are really good. And there is a medieval Italian recipe for sardines with salt and oranges, which I make all the time. It's great.
I noticed that in Chinese restaurant, there's no salt shaker on the table. So there's salt that's apparently infused into the condiments, I guess.
Well, for the Chinese way of thinking, and it's not a bad way of thinking, actually, the chef decides what the food should taste like.
What a concept.
Yeah. Of course, then you get to the issue of what is the importance of individual choice, which historically has not been prized thing in China.
So, you know, early in Earth's history, it's very likely that the oceans were much saltier than they are today because they hadn't had the chance to have these long sustained and long earned salt deposits that then get land underneath the Earth and it locks them away. And all that salt used to be in the ocean. Oceans that then spread into the lakes and the valleys and when those dry up, the salt stays there, gets buried under however many layers of...
So the sea, so the ocean was much, much saltier.
Much saltier, very, it's likely that it was much saltier than it is now, perhaps twice as salty.
Could you have walked on it? Could you walk across the salty, salty ocean?
And so, so essentially because all the salt would have been in the ocean, you can do that experiment, take the salinity of the Dead Sea and you said you could sit in the water.
You could sit in it, yeah.
Yeah, so double, yeah, so double it.
Double the salt, we'll see what, what, what comes of it.
So, so think about it, that, back then, that's when life formed. So, life back then would have been quite salt-loving.
In its day. And what we wonder is whether the Jupiter's moon Europa has, it has a liquid ocean beneath a frozen icy top that has been liquid for billions of years. We're wondering if that's a salt, a salty, a salty lake.
With some of the same kind of life that existed here billions of years ago.
Possibly. And so, one day, I want to go ice fishing on Europa and find out what's...
I'll take you. I will fold all the stars and we will fly there.
Find out if anything comes up and licks the camera lens, because this is exactly what the conditions are that we've got, that spawned life here on Earth. When we come back in our final segment, there's more on what role salt has played in our lives and what salt might be in our future. See you in a moment.
Welcome back to StarTalk Radio. I'm your host, Neil deGrasse Tyson. And I'm here with my co-host, Eugene Mirman. And we've been trying to discuss and figure out and...
Salt?
Probe, probe how salt has flavored human history.
I like that that's every, every back...
I'm trying to just, you know, just try to pun it out there. So, you know, have you been to like Whole Foods lately? You can go to like the salt section and you get salt in like 10 different colors. Have you, have you done this?
Uh, no, but I'm aware of that. I'm aware of lots of different kinds of salt and colors and flavors and like, you know, like smoked salt and stuff like that, truffle salt.
Salted salt.
Truffle salt.
That's a thing. That's a thing. I think I have it.
You got to preserve the salt somehow, so...
I think it's that flavor not to keep salt salty.
So of course, not all of them are white. Some are black, blue, red, green, yellow. And in fact, some dyes actually come from salt.
And when I spoke with Mark Kralansky, he wrote, of course, Salt, A World History, and we've been using clips of my interview with him for both of these hours. I asked him about the colored salts, because I see it in grocery stores. And I wonder, you know, they make these sort of backhanded claims like the colored salt is healthier than the regular salt, because you find all these colored salts in the healthy parts of healthy stores, right?
What do they claim it like it's like, like a magic? Like, what do they claim that it does? Like, healthy how? Like, less?
I don't know. I'm just-
Does Mark know?
Saying.
I hope Mark knows.
Let's find out what Mark Kralansky says about other stuff that you find in salt, some of which changes its color.
A sea salt holding tank is just a piece of seabed that's dammed off, and whatever is in the bottom of that bed, sand, dirt, minerals, can get into the salt. And then there's a process. You can wash salt, because salt has lots of amazing properties. And one of them is that it will only hold water to a certain point. And so if you have enough of a density of salt, the water can go through it without washing it away. So you can wash salt. And it used to be, until modern times, a goal of salt producers to try to get all that stuff out and try to get it as white as possible. The gray salt of Guerin in Brittany, which is now very fashionable, and health people
keep telling you, eat this, because the gray is so good for you. It was considered a huge problem, and the French government tried to work with them to clean it up, because the Spanish were outselling them, because they were able to get their salt whiter.
But I go now to Whole Foods, and there's a wall of salt, and it's a spectrum of salt colors: pink, blue, gray.
Yeah, all of these colored salt is history reversing itself. The red sea salt from Hawaii, the Polynesians never ate it. And if you read James Cook's diaries-
The explorer, James Cook.
The British explorer, traveling in the Pacific, found that Polynesians had this red sea salt. He tried to eat it, and he wrote, "This stuff tastes terrible." But what he didn't understand is they weren't eating it. They were using it in rituals.
And do you know what made that one red?
Clay. There used to be all kinds of different salts and all kinds of different colors. Every color is an impurity. Sodium chloride is white. And then they figured out, largely the Morton Company, how to make salt consistent both in crystallization and in color, and make all salt the same. And we had that for a half a century. And then, I guess, everybody decided this was boring. And now people, they want to have salt that's different colors. And, you know, a lot of this stuff was the rejects of early industry.
So when in doubt, just sell it at a Whole Foods nature place and people just buy it up?
Yeah, absolutely. And, you know, it's fine. It's not bad for you. But I find the claim that it's better for you to be a little bogus.
So all the colors are just like dirt and sediment left over in the salt?
I didn't know that there was a world of people trying to make salt more fun. I didn't know that that was like a thing you could choose to do with your life.
Well, other things, did you know that because our body has very high salinity, salt water is a very good conductor of electricity, which makes you an awesome target for lightning?
That's why lightning loves people so much.
That's why.
And hates cats because they're just not as salty.
Lightning would much rather go through you than through the air. And if you had the option to reach the ground and you provide six foot of nice, conductive, salty, lick body fluid, it'll go sideways into you to get to the ground rather than go from the ground to the cloud as it, you know, lightning strikes backwards.
Yeah, it starts at the ground and then it flies up.
Out of my hands. So in a way, you can shoot lightning as a person. You just do it once and then you probably burn.
And plus, you know, there's all these sort of wet, wet invertebrates that don't like salt, like slugs. Have you ever put salt on a slug?
I have not. Would, I haven't. And I also don't know what it does. But when we were talking.
I don't see how that's possible.
Well, I don't see how.
You're a comedian. How could you have never done this?
Well, I think it's funny is the amount that you think it would be more reasonable than I had put salt on a slug. Because I don't know, I mean, I don't know where you get a slug. Like, it's not like I grew up like in a sluggy, I didn't grow up in a forest raised by wolves and slugs. What happens when you put salt on a slug?
It doesn't like it. Yeah, you kill the slug.
You kill it? Because what happens?
Well, it shrivels up. It sucks out all the water from the slug.
You know, if you light it on fire, same thing.
I'm gonna stop there. I need a tweet of the week. We're running, that's the end of our hour here. How about, I got one, right? How about oceans, lake beds, mines, grocery stores, blood, sweat and tears, exploding stars, sources of sodium and chloride when you need it. That is my StarTalk Tweet of the Week. You've been listening to StarTalk Radio, brought to you in part by the National Science Foundation. Find us on the web at StarTalkRadio.net. I tweet at Neil Tyson. Eugene Mirman tweets at Eugene Mirman.
Thanks Eugene for another episode of StarTalk Radio. As always, keep looking up.
Page updated October 26, 2026 · transcript and summary are machine-generated
