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Screen capture from the TED-Ed video, How sugar affects the brain

Screen capture from the TED-Ed video, How sugar affects the brain

STEM in Context

How Sugar Affects the Brain

Digital Programs Team
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6.88
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Summary

Consuming sugary foods and drinks activates your brain’s reward system - the same system that can cause addiction.

How many people do you know who love desserts? Or candy? Or soft drinks? 
Why do people love sugary foods and drinks so much? Why do most of us not have the same love for, say, broccoli? The answer lies in your brain!

What is sugar?

Sugar is a class of molecules called carbohydrates. It appears in all kinds of food and drinks. It has many different names: sucrose, fructose, maltose, and dextrose, just to name a few. Check the labels in your kitchen cupboards. How many foods there have at least one of these ingredients?

You might be surprised to learn that sugar isn’t just in sweets! When you look through your cupboards, you might notice it in sauces and various snacks as well.

What happens in your brain when you eat sugar?

When you consume something that contains sugar, the sugars activate your sweet-taste receptors. They’re on your taste buds, which are on your tongue.

These receptors send a signal to a part of your brain called the forebrain, which is mostly comprised of the cerebrum. The forebrain then signals to many other parts, including your cerebral cortex. The cerebral cortex is the outer layer of the cerebrum.

Your cerebral cortex has many different jobs. One of them is processing sensory information. So when your sweet-taste receptors activate, your cerebral cortex gets the signal. It understands that you’re tasting something sweet. 

The three main parts of the brain include the cerebrum, cerebellum and brainstem. The cerebral cortex is the outer layer of the cerebrum
The three main parts of the brain include the cerebrum, cerebellum and brainstem. The cerebral cortex is the outer layer of the cerebrum (Source: Let’s Talk Science using an image by marina_ua via iStockphoto).

 

But that’s not all that activates. Your brain’s reward system also gets the signal. This reward system is a network of chemical pathways spanning your whole brain. 

Dr. Nicole Avena is a neuroscientist who studies nutrition and addiction. According to her, the reward system’s job is to answer the question, “Should I do that again?” That wonderful feeling you get when you eat sweets is your reward system’s way of saying, “Yes, do it again!”

Did you know?

Your brain’s reward system activates for all kinds of different reasons unrelated to food. It may activate when you hang out with your friends or a crush. It also plays a big role in addictions to things like drugs, gambling, and video games.

Sometimes, this reward system gets overactivated. In that case, you start to get cravings. Your tolerance to the substance you crave goes up. That means you need more of it to get that same sense of pleasure.

What is dopamine?

When dopamine-producing nerve cells receive nerve impulses, they release dopamine, which is a neurotransmitter. Cells with dopamine receptors are all over the brain
When dopamine-producing nerve cells receive nerve impulses, they release dopamine, which is a neurotransmitter. Cells with dopamine receptors are all over the brain (Source: Let’s Talk Science using an image by normaals via iStockphoto).

Dr. Avena describes dopamine as “the currency of our reward system.” Dopamine is a neurotransmitter. Dopamine receptors are all over your brain. But there are large clusters of them along your reward pathway.

Addictive substances tend to activate those receptors. That’s how addiction happens.

Many drugs cause these centres to become activated. Can you guess what other substance does this? That’s right - sugar! 

A delicious, healthy meal can spike dopamine levels, too. But if you eat the same meal over and over again, you’ll get less and less of a dopamine rush. That’s because your brain has evolved to notice new or different tastes. Your ancestors did not have best-before labels on their food. So they needed to be able to notice if their food had gone bad. Also, your ancestors evolved to eat a wide variety of food. The wider the variety, the more likely they were getting all of the nutrients they needed.

So what happens if you eat too much sugar?

There are also sugar receptors in your gut. So when you ingest something sugary, the receptors there are activated, too. They signal to your brain that your body should produce more insulin. Insulin is a hormone that regulates the amount of glucose (sugar) in your blood. The more sugar you eat, the more insulin your body needs to help regulate it.

Eating a little sugar now and then won’t necessarily hurt you. But if you eat too much sugar, your dopamine response will not level out. You’ll crave sugar, you’ll need more and more of it, and eventually you might become addicted. So do with sugar what you do with all the good things in life: enjoy it in moderation!

Starting Points

Connecting and Relating
  • Think about a time when you ate too much sugar. How did you feel?
  • Have you ever heard of a “sugar rush” or a “sugar high”? What does this mean to you?
  • Do you try to limit the amount of sugar in your diet? Why/why not?
  • Do you think that school lunches should be reduced in sugar? Sugar-free? Explain.
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Relating Science and Technology to Society and the Environment

  • Why do you think companies want to add sugar to their products? 
  • Should companies that manufacture products high in sugar be held accountable for medical issues, such as diabetes and obesity, that their customers experience? Explain.
  • Is it ethical for companies to add more sugar to products so that people become more addicted and buy more? Explain.
Exploring Concepts

  • What parts of the nervous system are activated when you eat something sweet?
  • What causes addiction to substances such as sugar?
  • What is the purpose of the “reward system”?
  • Why do people sometimes crave foods such as sugar?
Media Literacy

  • There are many commercials about products high in sugar (soft drinks, candies, etc.). Who are these commercials aimed at? Why do you think this is the case? 
  • Do you think the number of commercials that promote foods high in sugar should be limited? Why/why not?
Teaching Suggestions:
  • This resource supports teaching and learning of biology, anatomy and health related to the nervous system and carbohydrates. Concepts introduced include sugar, carbohydrates, receptors, forebrain, cerebrum, cerebral cortex, dopamine and reward system. 
  • To apply information from this resource and consolidate learning, teachers could have students use a Write-Around Discussion learning strategy.  Download ready-to-use Write-Around Discussion reproducibles using the Write-Around Discussion learning strategy for this article in [Google doc] and [.pdf]
  • To consolidate learning and practice questioning skills, teachers could have students use a Question-Answer Relationship learning strategy. Download ready-to-use Question Answer Relationship reproducibles for this article in [Google doc] and [.pdf].
  • To explore the functions of the brain, students could complete the Bullying and the Brain Case Study. In this case study, students learn how to interpret MRI brain scans and to identify the functional regions (i.e. lobes) of the brain most likely impacted by bullying behaviour.
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Learn more

Hey Sugar! Infographic (2014)  Visually - Contains information about the recommended intake of sugar, hidden sources of sugar, and where most of your sugar intake comes from 

How much sugar should we eat?  Royal Society of New Zealand - Article containing information about hidden sugar sources, the amount of sugar we should eat, and the difference between natural and added sugars; contains infographics. 

References

IFL Science. (n.d.). Here’s What Happens To Your Brain When You Give Up Sugar For Lent. Retrieved from https://www.iflscience.com/brain/here-s-what-happens-your-brain-when-you-give-sugar-lent/

Linden, D. J. (2011, March 30). Food, Pleasure and Evolution. Retrieved from https://www.psychologytoday.com/us/blog/the-compass-pleasure/201103/food-pleasure-and-evolution

Newton, P. (2009, April 26). What is dopamine? Retrieved from https://www.psychologytoday.com/us/blog/mouse-man/200904/what-is-dopamine

Reichelt, A. (2017, February 22). Fact or fiction – is sugar addictive? Retrieved from https://theconversation.com/fact-or-fiction-is-sugar-addictive-73340