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From sucrose to high fructose corn syrup to... lead? Hank gives us the sweet and lowdown on sweeteners.

Hosted by: Hank Green

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 Intro (0:00)


Hank: Humans love sweet things, we've evolved to value sweet foods when we come across them, but in a relatively short amount of time we've learned how to make things sweeter artificially. In some ways this is obviously amazing because it's delicious, but in terms of our health and the science of food it's been... confusing. Our brains still think we're getting sugar even when we're not and we can be a little judgy about what we think sugar does to people's behavior - especially kids - so to give some more context to what we know about humans and sweetness we wanted to put our videos about sugars and sweeteners here together in one place. First, from one of our earliest SciShow video: Why do we love sugar?

 Why do we love sugar? (0:48)

This, my friends, is your run-of-the-mill table sugar. It's made either from sugar beets or from sugar cane; there's no way to tell which. But henceforth, we're going to be calling it by its proper name, which is sucrose.

So, there's a bunch of different kinds of sugar, but they're all sweet-tasting edible carbohydrates. Ah, carbohydrates! Probably the tastiest word in the English language. And aside from filling up your snack hole and making your kids get all spazzy, sugar is one of the most important chemicals on the planet. It's pretty much the primary source of energy for everything on Earth. Not this stuff exactly - this stuff is more the primary source of all cavities on Earth. At the cellular level, pretty much every living thing on Earth, when it needs an energy fix, whether it's a plant, an animal, or a bacterium, the first thing they turn to is sugar.

Now, where does sugar come from - or at least, where does the energy used to create sugar come from? That, of course, is our friend the Sun. These lovely sweet compounds are found in every single plant, though in vastly varying quantities, of course, because it is the primary product of photosynthesis. (I'll be talking all about photosynthesis on the Biology Crash Course channel, and when we do that episode and post it online, you will see a link down in the description if you want to learn more about photosynthesis. But for now, let's just say that the importance of plants turning carbon dioxide and water and sunlight into sugar cannot be overstates.)

Basically, plants use energy from the Sun to split molecules of water, and the hydrogen from that water is combined with the carbon dioxide to create glucose. So in a fact, this whole process captures the energy of the Sun and stores it as chemical energy in sugar. I'm eating the Sun! I'm eating the Sun, right now. It's under my tongue. Problem! That was a lot of sugar. I'm worried I'm gonna have a stomach ache.

In addition to glucose, another common plant sugar is fructose, which has the same chemical formulas, just rearranged a little bit, and even though they're very similar and contain the same amount of energy, fructose actually tastes significantly sweeter, which is why we like to put high-fructose corn syrup into beverage. That's why we get a wide range of tastiness in plants, from super-sweet potatoes to not-sweet-at-all potatoes, which is what we generally call starch, which is a complex carbohydrate - actually bunch of sugar molecules all linked together, all the way to the sugar in sugar cane, which is our old friend sucrose, which is actually just a molecule of glucose and a molecule of fructose linked together. Point is that all of these sugars are important.

The reason why we think they're so delicious is because we need energy to survive and sugar is a really great place to get energy from. And if it seems to you like I've been eating a lot of sugar in this video, keep mind that I've maybe had two, three teaspoons so far. The average American has about 22 per day, so I've got a long way to go. 22 teaspoons a day, people! That cannot be healthy.

I did a little bit of research, and I discovered last night that, just from drinking soda, the average American drinks about 50 pounds of sugar a year. We Americans generally have a heck of a lot more sugar than we need to have. We should probably be having more like 6 to 9 teaspoons a day, so you might wanna rethink that all Cap'n Crunch diet you're currently on.

We're not really designed for a world where sugar is infinitely available. It's certainly pretty hard to come by something really sweet in nature, and even if you find something, like a bunch of apples, it's hard to eat a lot of apples without making yourself pretty sick. Nowadays we've gotten around that by producing this wonderful white powder as well as the high-fructose corn syrup that they put in absolutely everything these days.

So, if you want my health advice, try and maybe eat the way that your caveman ancestors did - fruits and vegetables, maybe some complex carbohydrates here and there. And I would suggest overall to not consume sugar in this manner. [pours sugar straight into his mouth]

Now, 2012 Hank just mentioned in that episode that fructose is much sweeter than sucrose, but they are both plant sugars. So why all the hate for high fructose corn syrup? Well, here's a video about that very thing.

 High Fructose Corn Syrup (4:14)

People just seem to love to hate stuff that tastes good these days. Sometimes there's a good reason for it of course, but sometimes I feel like, we're just, we're just giving ourselves a hard time.

When I was a kid for example, every kitchen I ever went into was full of fat-free stuff because everybody's mom had heard on some morning show that if you eat anything with fat in it you're going to turn into an overstuffed, walrus-shaped couch cushion. So we all just ate things like bagels slathered in margarine and sometimes I'd come home from school and eat a whole box of fat free cookies because they're fat-free, it doesn't matter how many you eat. Why do we even do this?

So now people are eating fatty things again and I mean, thank god. [EATS CORN DOG WITH SPRAY CAN CHEESE ON TOP] That wasn't good. At the moment though instead of fat the new Dark Lord of Nutrition is high-fructose corn syrup. And I checked, this no high fructose corn syrup in this corn dog. People despise it, we've gotten so up in arms that food companies are now kicking it out of their products and replacing it with "all-natural sugar". To hear a lot of people tell it, HFCS - as people have started calling it to make it sound more "chemical-ly" - is the enemy of all things good and pure and the sole cause of the obesity epidemic.

Speaking of the obesity epidemic, I did a whole show on that, you show watch it. [MOTIONS TO LINK TO OBESITY VIDEO]

Anyway, you know, as they say on the internet, haters are gonna hate. (Do they say that on the internet or is that an urban slang thing?) But do the haters have a valid point? And we've been doing research on this and we're not quite sure actually.

So high fructose corn syrup is kind of a wonderful creation, really. It's extremely inexpensive, it's easy to transport, easy to mix into things, it's made food a lot cheaper. It's certainly made every calorie that we eat in America cheaper. This is of course all with the help of 40 billion dollars of subsidies to corn farmers. For all these reasons and more, the use of high fructose corn syrup has been skyrocketing since the 1970's and now if you're eating something sweet there's about a 50% chance that that sweetness is coming from high fructose corn syrup.

That said, on the surface of things, sucrose, which we know as cane sugar or "all-natural sugar" or table sugar and high fructose corn syrup are basically the same thing. They're both plant-based sweeteners and on a molecular level, they're pretty similar. Both sugar and high fructose corn syrup are made out of glucose and fructose. Chemically, sucrose is just as glucose molecule and a fructose molecule bonded together, while high fructose corn syrup is just a mixture of glucose and fructose molecules without them being bound together.

But molecule for molecule, fructose actually tastes a lot sweeter to us and I should point out that fructose is called fructose because it's the kind of sugar that we generally find in fruits. So if high fructose corn syrup is basically just glucose, which is the most common sugar in the universe and fructose, which is the kind of stuff that you find in apple juice, how could it be that bad for you? What makes us so suspicious?

[TALKING WHILE GRAPH IS SHOWN] Well, we have this graph right here. Yeah that's the obesity rate in America going through the roof right about the same time that every single product in the grocery stores started getting enhanced with high fructose corn syrup. And that is a correlation, not a causation, but it is correlation worth investigating.

For example, some recent studies on rats are beginning to show that high fructose corn syrup makes the rats waaaaaay fatter than if they just ate table sugar. And it's also raising levels of fat content in their blood. But there have been a lot of other studies that have shown no significant change depending on whether you're eating table sugar or high fructose corn syrup.

One thing, however, is certain, that high fructose corn syrup is in a lot of what we're eating these days. It's making sweet food much less expensive and so the barrier to eating them is lower and it is very rewarding to have a nice, cold Coca-Cola.

So there's a combination of economics, biochemistry, brain chemistry and in general, people eating sugar of all kinds, which probably isn't very good for us.

But it's not just about table sugar vs. high fructose corn syrup. Nowadays, there are tons of different ways to sweeten things artificially and each way binds with our taste receptors differently. Here's more on the science of sweetness.

 The Science of Sweetness (7:56)

So you've got your tongue (at least, I hope you do) and it's covered with tons of lingual papillae, commonly known as taste buds, which are what make eating so enjoyable. Taste buds are chemoreceptors, which means that they translate the biochemical make up of food into electrical signals so the brain knows what it's tasting. Each taste bud is made up of clumps of 50 to 100 taste cells, proteins that bind with food molecules to allow us to detect specific flavors. In general, humans tend to go for salty and sweet stuff and avoid overly bitter and sour tastes. Probably because in nature those tastes often indicate that a potential food is poisonous. Physiologically, the body associates sweet taste with high calorie and therefore high energy foods. It's desirable!

Most animals in the world can enjoy sweetness as well with the exception of those in the cat family. Cats can't taste sugar because they lack the genes that generate the sweet receptors. Perhaps because they evolved to only eat meat. Makes me feel kind of sorry for 'em. But of course we humans can't get enough of sweet, and we've got the dental, diabetes, and obesity issues to prove it.

Not only can we taste sweetness, but we are connoisseurs of its delicate range of flavors from the honey, agave, and maple syrup to fructose and glucose and plants and fruits and good old sugar-bowl sucrose, as well as more recent adaptations like high fructose corn syrup and the host of artificial sweeteners on the market. We can taste them all and, we can tell them apart.

Natural sugars trigger our taste buds immediately, filling our senses with all kinds of goodness before gently fading away without leaving any after taste. Chemically, it's a beautifully simple process, but it is maddeningly elusive to duplicate, which is why synthesizing the taste of real sugar has become a sort of holy grail quest for food chemists. So far no one, in my opinion anyway, has even come close.

That's because when you lick that beautiful powdered sugar off your fingers the sucrose molecules act like a key that unlock a sweet sensation on your tongue, and then your brain. Meanwhile, your digestive enzymes start metabolizing that sucrose, giving you energy to move around and do your happy dance. Of course, if you don't use all that energy it sticks around as fat.

Artificial compounds affect our taste buds in a similar way to natural sweeteners, but because their molecules are structured differently, they bind to our receptors much more aggressively. And so their sweetness comes across not as a gentle flavor fairy kiss so much as a slap in the tongue. Which is why saccharin tastes about 300 times sweeter than plain sucrose and can leave a metallic-like after taste.

Interestingly most other animals are unable to taste these artificial sweeteners because their taste buds are set up differently. Each artificial sweetener has a different molecular shape, so each binds to our taste receptors in a distinct way, giving a signature flavor to their unnatural sweetness. That's why a typical diner will have a colorful display of different packets ready to sweeten your coffee.

And one thing almost all of these lab created sweeteners have in common is that they don't contain any calories or energy because our bodies cannot metabolize them. So they just slide through your guts without being absorbed. Some kinds are low-calorie but they're so bonker-sweet they just a dab'll do you so even if they are metabolized, its caloric pay-off is negligible.

So now let's take a quick look at what's going on in that table ramikin-rainbow. First, we got your average Joe packet of white sugar-bowl sugar, or sucrose. This white stuff is either refined from sugar cane or sugar beets, and there is no way to tell which it was by the time it reaches the packet phase, but it is chemically the same thing.

If you're in like a new-fangled hippie café, there may be a green packet in the mix: that's stevia, the new guy. Stevia is derived from the sweet-leafed stevia plant, a perennial shrub native to Paraguay and Brazil. The stevioside compounds that make its leaves sweet can be isolated and refined into an intense powder. Stevia is calorie-free, because our bodies can't metabolize it, just like the synthetics. This makes it very low on the glycemic index, meaning it doesn't raise your blood sugar, even though it's 300 times sweeter than sugar, so they have to actually cut it with other stuff. While South Americans have been using stevia for ages, it's pretty new to the US market and only recently did the FDA approve it as a food additive.

Now if you're sitting at the table drinking coffee with your grandad, you might see him reach for a pink packet of saccharin. The first and oldest of all the artificial sweeteners, saccharin was accidentally discovered in the late 1870s by a chemist working with coal-tar derivatives. One day he forgot to wash his hands, and noticed that night at dinner that his fingers tasted sweet. This is going to be a repeated story throughout this episode. Teddy Roosevelt was a big fan of saccharin, and it gained popularity during WWI when sugar was scarce. In 1957, it was branded as Sweet'N Low.

If you're old enough to remember your mom drinking cans of Tab soda, you may remember anything containing saccharin used to come with a warning label declaring that it may cause cancer. A bunch of lab tests in the 1970s linked saccharin to bladder and other cancers in rats, and the FDA tried to ban the stuff in 1977, but Congress intervened and suggested that it carry a warning label instead. Which hardly kept people from drinking it; after extensive lobbying from the diet food industry and sufficient claims that earlier studies were flawed, the label was removed in 2000. It's still the same compound, though, so it's more or less up to you to decide what you make of all that.

Next to the pink come the blue sachets of aspartame. It was discovered in the 1960s when, yes, another chemist absentmindedly licked his finger to grab a piece of paper while testing a new ulcer medication. Thank you, sloppy chemical technique. Aspartame popped up in products in the early 1980s as an alternative to saccharin. It's about 200 times sweeter than sugar and unlike other synthetics, our bodies can metabolize it, so it does have a few calories. Once digested, aspartame breaks down into three components: the amino acid phenylalanine and aspartic acid as well as methanol, which is better known as wood alcohol.

And finally, you have that sunny yellow sucralose. Sucralose was originally marketed as tasting like sugar cause it's made from sugar, and it is — it's made by reacting sucralose with chlorine: a toxic chemical. It, too, was accidentally created in the mid 1970s in London. A student and his advisor were working on a new DDT-like insecticide by slowly adding the toxic chemical sulfuryl chloride to a sugar solution. The resulting reaction formed a new compound: tetradeoxygalactosucrose. Then, as legend has it, the student was told to test the product, but misheard, and tasted it instead. It was crazy sweet; it was sucralose.

To make sucralose, you have to replace some of the oxygen and hydrogen groups in a sucralose molecule with chlorine atoms, at which point it isn't sugar anymore. But it is 600 times sweeter. Those chlorine particles prevent us from metabolizing sucralose, making it calorie-free, and it also makes the molecules heat-resistant enough to be used in baking, something other artificial sweeteners can't handle.

Maybe by now you're wondering about the potential risks you've heard associated with artificial sweeteners. So...are they safe? Or what? Well first, remember that anything you buy at the grocery store to sprinkle on your cereal has been tested and approved, and is regulated by the FDA as being safe...enough. Even if it uses toxic chemicals in the processing, it's not a toxic chemical itself. However, a lot of people are still wary of these lab creations, including some of the researchers that make them.

Critics argue that these products haven't been around long enough to truly measure the cumulative effects of a lifetime of consumption. Some new studies are suggesting that certain products may not be as benign as we once thought. A European Union funded study published in 2010, for instance, found that pregnant women who drank diet sodas appeared to be at greater risk of premature birth, while other research on aspartame linked it to several types of cancer in rats. And yet other studies have found that daily diet soda intake substantially increased the risk of type 2 diabetes. And that's one of the potential health effects that's getting a lot of attention these days.

Specifically, researchers are looking at how artificial sweeteners can interfere with the brain's natural ability to count calories, which can actually lead to weight gain. I mentioned before that the tongue and brain associate sweet things with calories, which are straight-up energy. The brain knows how many calories the body needs to get by, so it understands that a) a banana tastes sweet, and b) it gives a certain amount of energy to keep me satiated for a certain period of time, so I can stop eating now. But the theory is that artificial sweeteners are basically dirty rotten liars when it comes to your brain. Guzzling a gallon of diet soda only retrains your body to stop associating sweetness with calories. Pretty soon, you're eating that banana again, and the brain underestimates the true calorie count of said banana, and wants to keep eating.

One study found that rats fed artificially sweetened yogurt with their normal rat chow gained more weight than those eating sugar-sweetened yogurt. It was like the artificial sweeteners were deprogramming the animal's natural ability to keep tabs of its calorie intake. Your brain is used to associating sweetness with calories and calories with satiation; sweetness without calories can confound the brain and potentially lead to more craving and overeating. We may fool our tongues, but we can't fool our brains. So in the end it's up to you what you want to put in your body, but any way you swing it, moderation seems to be the key.

Now in that episode I kind of lied to you. I said that saccharine is the oldest of the artificial sweeteners but in truth there is an artificial sweetener that is even older: lead. Also more deadly.

 Lead: The original artificial sweetener (16:57)

As elements on the periodic table go, lead is pretty handy. It's not exactly oxygen or nitrogen, but it has some admirable qualities. Like, it's heavy but soft and malleable, in the form of lead dioxide, it's highly conductive, which makes it useful in batteries, and it's so incredibly dense that it's great at blocking out things like ionizing radiation. Lead is good for all sorts of things, but it is also poisonous, really, very poisonous, and for the last 5000 years of so, humanity has been so enamored of all of its wonderful traits that we've been killing ourselves with it.

When inhaled or ingested, lead is readily absorbed into the blood, where it can slow down the transport of oxygen and eventually build up in your kidneys, brain, liver, heart, and especially bones and teeth. Once it's in the body, lead not only displaces metals you actually need, like calcium, iron, and zinc, but it's excellent at blocking receptors for glutamate, the most important neurotransmitter for normal brain function and learning. Lead poisoning can affect nerve transmission to the brain and cause abdominal pain, anemia, and the loss of developmental skills in children.

So what makes this naturally occurring heavy metal so valuable that we overlooked its terrible side effects for so long? Well, because of its nice combination of softness, durability, and availability, the ancient Romans and Greeks used lead in practically everything, from their plumbing and eating utensils to their writing tablets. But the Romans in particular really liked to eat it.

Don't test this out, but lead actually has a naturally sweet taste, and Romans sprinkled lead acetate into their wine to sweeten it. They called it sapa, and it was consumed in massive quantities by the aristocracy. It was also found to be an effective preservative because, you know, it kills stuff. According to some historians, the common use of this lead additive caused widespread infertility and dementia in ancient Rome, especially among the ruling class. So think about that next time you're wondering whether aspartame is bad for you; the Romans wanted sweeter wine so bad they put lead in it.

Lead has been used in paint for thousands of years as well, and it's so useful that we kept using it through the late twentieth century, well after we understood its dangers. In particular, lead carbonate, otherwise known as white lead, was widely used because it made paint so opaque that a small amount of lead-based paint could cover a large area. It's also highly insoluble, meaning it doesn't dissolve in water, making it great at resisting the moisture and mildew that can cause other paints to crack over time. Lead carbonate can prevent decomposition in the oils that make up paints, allowing them to look fresh longer, and lead-based paints dry faster than their counterparts.

There was so much to like about lead paint, except for the part where it killed a bunch of people - because people did get poisoned from lead paint, especially children, either from inhaling dust with flakes of the paint in it or jut because, as previously mentioned, lead makes things sweet and kids like sweet things, even if the sweet things are paint chips. The federal government finally banned the use of lead in paints in the U.S. in 1978, but lead was still all over the place, particularly in the air, because of cars.

In addition to its uses as a wine sweetener and a paint improver, lead offered even more benefits as a gasoline additive in the form of a compound known as tetraethyl lead. In the early 1920s, car-makers were looking for a solution to engine knock. The engines work best when the fuel in the cylinder burns all at once and at the exact moment the spark plug fires, but sometimes, especially in older cars or with cheaper fuel, the fuel would actually ignite before the spark plug fired, damaging the pistons and cylinders in the engine and making an audible pinging noise. The tetraethyl lead increased the ignition temperature of the gasoline, eliminating pre-ignition, but, of course, the lead was released in the car's exhaust, which was then inhaled by people and absorbed into their bloodstreams.

As with paint, it took a while for the problems associated with leaded gas to show up, but some clues came early, like the fact that workers who handled tetraethyl lead often experienced hallucinations and many of them died at a young age. So in 1974, the Environmental Protection Agency developed guidelines for eventually eliminating leaded gasoline. It wasn't easy; other additives had to be developed for cars that had been designed to run on leaded gasoline, many of which had their own problems, but in 1996, the last leaded gasoline was sold in the United States, and most gas stations still use labels to assure everyone that even their cheapest fuel is unleaded.

So quick review: if you're using lead to shield yourself from X-rays or make batteries or something like that, you're probably doing it right, but if you're using lead in any way that winds up in your mouth or up your nose or in any of your face holes, then you're using it wrong.

So yeah, lead is sweet, but there is nothing about it that is good for you. Now, if you remember back in the beginning of this video, 2012 Hank made a crack about sugar making kids hyper. Well, it turns out kids can just be that way no matter what. The real interesting thing is how we, as adults, perceive kids when we think they've had sugar. This last video gives use the Sweet-and-Lowdown on kids and sugar.

 Kids and Sugar (21:38)

If you heard it once you heard it a thousand times: parents blaming their kid's unfortunate behavior on sugar. And if you've been around kids long enough you could probably see why people make that connection: I mean, a healthy and happy five-year-old wakes up perfectly fine, has a good morning and then goes to a birthday party, becomes a shrieking, moody ball of pure energy, and of course it's all from the cake and sugary drinks and ice cream, right? Right?! What else could it be?

As it turns out it's probably just from hanging out with a bunch of other five-year-old's and then being pulled away to go home and be bored the rest of the day. The kid would probably act the same even if they had no sugar at all. As far as science is concerned there is no evidence that sugar intake makes healthy people more active. Not even children! On the contrary: lots of studies have shown that what looks like sugar-based excitability is really just normal psychological response to a stimulus, i.e. getting a delicious snack.

Several groups of researchers have found that the "sugar rush" we have often come to associate with candied-up kids, actually exists just in the perceptions of observers, especially parents and other care-givers.

In one double-blind study, young boys and their mothers were divided into two groups. One group was told that the boys would be given a sugary drink, and the other was told that they would be given a drink sweetened with aspartame, the sweetener in Equal. But it was a lie! In reality both groups got the artificial sweetener. After enjoying their little drink, the boys and their mothers were told to just play around for a while, and then the mothers were asked how they thought playtime went.

Almost invariably the mothers who thought their sons were given sugar described their behavior more critically than those who thought their sons had been given an artificial sweetener. And maybe even more importantly, neutral observers in the study described the mothers described in the sugar group as hovering more closely around their boys and being more critical or what they were doing, but really both groups of kids were just playing, just being kids.

Because of studies like this the National Institutes of Health has said that there is no link between sugar intake and hyperactivity in children. But that's not to say that eating loads of sugar can't affect a person's activity level, at least for a little while.

Sugar enters the bloodstream almost immediately after it's eaten, and it can be used if we are currently active. But our bodies are really really good at regulating the amount of sugar in our blood, so almost as soon as it's absorbed it's metabolized or stored, otherwise our blood sugar would be totally nuts, which it is only if we have diabetes.

The sugar intake doesn't cause you to be more active, it only allows for a bit of extra energy if you're burning up a bunch of energy already.

So long story short: sugar is delicious and I'm glad it exists. Like almost anything it can be misused and overused and when that happens it can cause lots of problems. But in the end one thing we can't blame on sugar is our behavior, or that of our kids. With or without sugar, sometimes you just gotta go wild, man.

 Outro (24:19)

Thanks for watching this extra-sweet SciShow compilation video. If you want to see a compilation of a certain subject or have questions about sugar that we didn't cover, let us know in the comments and don't forget to go to and subscribe.