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Hank talks about a sweet-tasting substance we humans just love - where it comes from, why we need it and how we could maybe stand to love it a little less.

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CrashCourse Biology Photosynthesis episode:

Hank Green: I'm holding in my hands one of the most magnificent, powerful, marvelous chemicals in all of the universe. I'm wondering if you would be okay with me if I just have some. [eats sugar] Mm! It tastes so good.

[intro music]

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 crystals straight into his mouth]

Thank you for watching this episode of SciShow. If you wanna learn more about sugar, check the links in the description. You can also ask us questions, which we'll be happy to answer, and suggest other topics for SciShow in the YouTube comments, and you can hook up with us on Facebook and Twitter as well. Goodbye.

[outro music]