We love sweet treats. But too much sugar in our diet can cause weight gain and obesity, type 2 diabetes as well as tooth decay. We know it’s best to avoid sweets, ice cream, cookies, cakes, and soft drinks, but sometimes it’s very hard to resist. It’s as if our brain is programmed to want these foods.
My research in neuroscience is about how modern obesogenic food – which causes obesity – affects the brain. I want to understand how what we eat changes our behavior and whether brain changes can be alleviated by other aspects of the lifestyle.
The body works with sugar-glucose to be precise. This term comes from the Greek glucose, which means sweet. Glucose feeds the cells that compose us, including those of the brain (neurons).
Sugar and dopamine outbreaks
Our distant ancestors were scavengers. As sweet foods are an excellent source of energy, evolution has made us particularly good. Foods with an unpleasant taste, bitter or sour may be poisonous, spoiled or not ripe enough, and therefore cause illness.
Thus, to maximize our chances of survival as a species, we have an innate brain system that leads us to love sweet foods that give us energy.
When eating sweet foods, the brain’s reward system – called the mesolimbic dopaminergic system – is activated. Dopamine is a chemical released by neurons that signals that an event is positive. When the reward system is triggered, it reinforces behaviors that are then more likely to repeat.
Sufferings of dopamine caused by sugar consumption encourage rapid learning, which leads us to prefer these foods.
Today, our environment is full of sweet and energy-rich foods. It is no longer necessary to go looking for them because they are everywhere. Unfortunately, our brain is still functionally similar to our ancestors, and he really likes sugar. But what happens in the brain when we eat too much?
Can sugar reprogram the brain?
The brain continually remodels its connections through a process called neuroplasticity. This reconfiguration can occur in the reward system. Repeated activation of the reward pathway by drugs or a large number of sugary foods causes the brain to adapt to frequent stimulation, which leads to a form of tolerance.
For sweet foods, it means eating more to get the same sense of satisfaction-a typical feature of addiction.
Food addiction is a controversial topic among scientists and clinicians. If it is true that one can become physically dependent on certain drugs, one wonders if this can be the case for food when it is needed for basic survival.
The brain wants sugar again and again
Regardless of the need to feed oneself to feed the body, many people experience cravings, especially when they are stressed, hungry or simply confronted with a nice display of cakes in a cafe.
To resist these cravings, one must restrain his natural tendency to want to indulge himself with tasty food. A network of inhibitory neurons regulates our behavior. These neurons are concentrated in the prefrontal cortex – an area of the brain involved in decision making, impulse control, and the ability to delay reward.
Inhibitory neurons are the braking system of the brain. They release GABA, an amino acid. Research on rats has shown that eating foods rich in sugar can alter inhibitory neurons. Sugar-fed rats find it harder to control their behavior and make decisions.
Thus, our diet can influence our ability to resist temptations, which is why it is so difficult to change diets.
In a recent study, people were asked to rate their desire to eat high-calorie snacks when they are hungry compared to the desire they had when they just ate. People who regularly eat high-fat, high-sugar foods said they wanted more appetizers even when they were not hungry.
This suggests that regular consumption of high-sugar foods may amplify food cravings – creating a vicious circle that leads us to eat more.
Sugar and the formation of memory
The hippocampus – an important area for memory – is another area of the brain affected by high sugar diets.
Research has shown that rats that eat high-sugar foods are less likely to remember if they have seen objects in specific places.
Transformations induced in the hippocampus by sugar are a reduction in the formation of neurons, essential for encoding memories, as well as an increase in chemical substances related to inflammation.
How to protect your brain from sugar?
The World Health Organization recommends limiting the intake of added sugars to 5% of our daily calorie intake, which is about 25 grams (six teaspoons).
Knowing that the Canadian adult eats an average of 85 grams (20 teaspoons) of sugar a day, this is a big change for many people.
It is important to note that the neuroplasticity capabilities of the brain allow it to reset to some degree after reducing its sugar intake, and physical exercise can improve this process. Foods rich in omega-3 fatty acids (found in fish oil, nuts, and seeds) are also neuroprotective and can stimulate the brain chemicals needed to form new neurons.
While it’s not easy to break habits like having a dessert after every meal or a coffee with two sugars, your brain will thank you for making positive gestures.
The first step is often the most difficult, but changes in diet usually become easier with time.