[00:06] Picture warm, gooey cookies,
[00:09] crunchy candies, velvety cakes,
[00:12] waffle cones piled high with ice cream.
[00:14] Is your mouth watering?
[00:16] Are you craving dessert?
[00:17] Why?
[00:18] What happens in the brain
that makes sugary foods so hard to resist?
[00:23] Sugar is a general term
used to describe a class of molecules
[00:27] called carbohydrates,
[00:28] and it's found in a wide variety
of food and drink.
[00:31] Just check the labels
on sweet products you buy.
[00:34] Glucose, fructose, sucrose,
[00:36] maltose, lactose, dextrose, and starch
[00:39] are all forms of sugar.
[00:41] So are high-fructose corn syrup,
[00:43] fruit juice, raw sugar, and honey.
[00:46] And sugar isn't just
in candies and desserts,
[00:49] it's also added to tomato sauce,
[00:51] yogurt, dried fruit,
flavored waters, or granola bars.
[00:55] Since sugar is everywhere,
it's important to understand
[00:58] how it affects the brain.
[00:59] What happens when sugar hits your tongue?
[01:02] And does eating a little bit of sugar
make you crave more?
[01:05] You take a bite of cereal.
[01:07] The sugars it contains activate
the sweet-taste receptors,
[01:10] part of the taste buds on the tongue.
[01:12] These receptors send a signal
up to the brain stem,
[01:15] and from there, it forks off
into many areas of the forebrain,
[01:19] one of which is the cerebral cortex.
[01:21] Different sections of the cerebral cortex
process different tastes:
[01:26] bitter, salty, umami,
[01:27] and, in our case, sweet.
[01:29] From here, the signal activates
the brain's reward system.
[01:33] This reward system is a series
of electrical and chemical pathways
[01:37] across several different
regions of the brain.
[01:39] It's a complicated network,
[01:41] but it helps answer a single,
subconscious question:
[01:44] should I do that again?
[01:45] That warm, fuzzy feeling you get
when you taste Grandma's chocolate cake?
[01:49] That's your reward system saying,
[01:51] "Mmm, yes!"
[01:52] And it's not just activated by food.
[01:55] Socializing, sexual behavior, and drugs
[01:57] are just a few examples
of things and experiences
[02:00] that also activate the reward system.
[02:03] But overactivating this reward system
kickstarts a series of unfortunate events:
[02:08] loss of control, craving,
and increased tolerance to sugar.
[02:13] Let's get back to our bite of cereal.
[02:15] It travels down into your stomach
and eventually into your gut.
[02:18] And guess what?
[02:19] There are sugar receptors here, too.
[02:22] They are not taste buds,
but they do send signals
[02:24] telling your brain that you're full
[02:26] or that your body should
produce more insulin
[02:28] to deal with the extra sugar
you're eating.
[02:31] The major currency
of our reward system is dopamine,
[02:34] an important chemical or neurotransmitter.
[02:37] There are many dopamine
receptors in the forebrain,
[02:39] but they're not evenly distributed.
[02:41] Certain areas contain dense
clusters of receptors,
[02:44] and these dopamine hot spots
are a part of our reward system.
[02:48] Drugs like alcohol, nicotine, or heroin
[02:51] send dopamine into overdrive,
[02:53] leading some people
to constantly seek that high,
[02:56] in other words, to be addicted.
[02:58] Sugar also causes dopamine to be released,
though not as violently as drugs.
[03:03] And sugar is rare
among dopamine-inducing foods.
[03:06] Broccoli, for example, has no effect,
[03:08] which probably explains
[03:10] why it's so hard to get
kids to eat their veggies.
[03:13] Speaking of healthy foods,
[03:14] let's say you're hungry
and decide to eat a balanced meal.
[03:17] You do, and dopamine levels spike
in the reward system hot spots.
[03:21] But if you eat that same dish
many days in a row,
[03:24] dopamine levels will spike less and less,
eventually leveling out.
[03:28] That's because when it comes to food,
[03:30] the brain evolved to pay special attention
to new or different tastes.
[03:34] Why?
[03:36] Two reasons:
[03:37] first, to detect food that's gone bad.
[03:39] And second, because the more variety
we have in our diet,
[03:42] the more likely we are
to get all the nutrients we need.
[03:45] To keep that variety up,
[03:47] we need to be able
to recognize a new food,
[03:49] and more importantly, we need
to want to keep eating new foods.
[03:53] And that's why the dopamine levels off
when a food becomes boring.
[03:57] Now, back to that meal.
[03:58] What happens if in place
of the healthy, balanced dish,
[04:02] you eat sugar-rich food instead?
[04:04] If you rarely eat sugar
or don't eat much at a time,
[04:07] the effect is similar
to that of the balanced meal.
[04:09] But if you eat too much,
the dopamine response does not level out.
[04:13] In other words, eating lots of sugar
will continue to feel rewarding.
[04:17] In this way, sugar behaves
a little bit like a drug.
[04:21] It's one reason people seem
to be hooked on sugary foods.
[04:24] So, think back to all those
different kinds of sugar.
[04:27] Each one is unique,
but every time any sugar is consumed,
[04:30] it kickstarts a domino effect in the brain
that sparks a rewarding feeling.
[04:35] Too much, too often,
and things can go into overdrive.
[04:38] So, yes, overconsumption of sugar
can have addictive effects on the brain,
[04:42] but a wedge of cake once
in a while won't hurt you.