A Neuroscientist Explains What Sugar Does to Our Brains

December 27, 2019

We love sweet treats. But too much sugar in our diets can lead to weight gain and obesity, Type 2 diabetes and dental decay. We know we shouldn’t be eating candy, ice cream, cookies, cakes and drinking sugary sodas, but sometimes they are so hard to resist.

It’s as if our brain is hardwired to want these foods.

As a neuroscientist my research centres on how modern day “obesogenic”, or obesity-promoting, diets change the brain. I want to understand how what we eat alters our behaviour and whether brain changes can be mitigated by other lifestyle factors.

Your body runs on sugar – glucose to be precise. Glucose comes from the Greek word glukos which means sweet. Glucose fuels the cells that make up our body – including brain cells (neurons).

Dopamine “hits” from eating sugar

On an evolutionary basis, our primitive ancestors were scavengers. Sugary foods are excellent sources of energy, so we have evolved to find sweet foods particularly pleasurable. Foods with unpleasant, bitter and sour tastes can be unripe, poisonous or rotting – causing sickness.

So to maximize our survival as a species, we have an innate brain system that makes us like sweet foods since they’re a great source of energy to fuel our bodies.

When we eat sweet foods the brain’s reward system – called the mesolimbic dopamine system – gets activated. Dopamine is a brain chemical released by neurons and can signal that an event was positive. When the reward system fires, it reinforces behaviours – making it more likely for us to carry out these actions again.

Dopamine “hits” from eating sugar promote rapid learning to preferentially find more of these foods.

Our environment today is abundant with sweet, energy rich foods. We no longer have to forage for these special sugary foods – they are available everywhere.

Unfortunately, our brain is still functionally very similar to our ancestors, and it really likes sugar. So what happens in the brain when we excessively consume sugar?

Can sugar rewire the brain?

The brain continuously remodels and rewires itself through a process called neuroplasticity. This rewiring can happen in the reward system. Repeated activation of the reward pathway by drugs or by eating lots of sugary foods causes the brain to adapt to frequent stimulation, leading to a sort of tolerance.

In the case of sweet foods, this means we need to eat more to get the same rewarding feeling – a classic feature of addiction.

Food addiction is a controversial subject among scientists and clinicians. While it is true that you can become physically dependent on certain drugs, it is debated whether you can be addicted to food when you need it for basic survival.

The brain wants sugar, then more sugar

Regardless of our need for food to power our bodies, many people experience food cravings, particularly when stressed, hungry or just faced with an alluring display of cakes in a coffee shop.

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