The Harmful Impact of Sugar on the Brain

The brain uses more energy than any other organ in the human body. This fact might lead you to the mistaken belief that sugar, a tasty, fast-acting supply of calories, is a good source of fuel for the brain. In fact, exposing the human brain to excessive sugar leads to harmful changes in how your brain works.

By tapping into the brain’s reward system that makes you feel good, sugar stimulates eating, making you more likely to overeat and putting you at risk of a host of problems, including cognitive decline, heart disease, diabetes, and other inflammatory diseases.

According to a review on the impact of sugar on behavior, excess sugar impairs both our thinking skills and our self-control. For many people, having a little sugar stimulates a craving for more. Everything in moderation goes out the window when you learn that foods high in added sugar don’t have that satisfying effect you’re craving. Instead they make you seek out more sugar in the same way as opioid drugs. Sweet foods, along with salty and fatty foods, are theorized to have addictive effects on the human brain, driving the loss of self-control, overeating, and fat gain.

How The Brain Regulates Eating Behavior

In our hunter-gatherer ancestors, the drive for sugar-rich foods was key to survival as food was scarce. In our environment where there is no shortage of high calorie, processed foods this has become a liability. It works like this: In normal situations, the hypothalamus regulates food intake to meet energy needs. However, there is another part of the brain that is receptive to the motivating reward of feel-good neurotransmitters like dopamine that also drive eating behavior.

The more pleasurable a food is, the more feel-good chemicals are released, encouraging food intake beyond necessary energy requirements.

By separating eating behavior from calorie needs, we are leading people to compulsively overeat as they strive for that feel good sensation that comes from sugar consumption. Foods high in added fructose are especially problematic.

The Different Kinds Of Sugar

Most added sugar comes from either fructose or sucrose. Sucrose is what we refer to as table sugar and it is half glucose and half fructose. Fructose is obviously pure fructose, but a more common source in the western food supply is as high-fructose corn syrup, which is usually 55 percent fructose with the rest coming from glucose.

Fructose is the primary sugar source found in fruit, which leads to the misconception that it is healthier. For one thing, the quantities of fructose in a piece of fruit and a sweetened beverage are drastically different. The fructose in a peach represents approximately 1 percent of the fruit’s weight whereas fructose accounts for over half the weight of high fructose corn syrup. Additionally, in fruit, fructose is accompanied by antioxidants, flavanols, potassium, vitamin C, and high fiber, which may collectively outweigh any negative consequences of fructose content.

Sugar’s Reward Response

Because most of the added sugar we eat is either high-fructose corn syrup or sucrose, we are consuming a significant amount of fructose on a daily basis. This is a problem due to how different forms of sugar are metabolized.

Glucose is absorbed in the top half of the digestive tract into the bloodstream. Through the action of insulin, it quickly passes through to muscle, fat, and other tissues like the brain, where it can be used for energy.

Fructose, on the other hand, is a less direct source of energy. Independent of insulin, the liver converts fructose to glucose, lactate, or fatty acids before passing it to the blood stream where it can be oxidized in other tissues for energy. Unfortunately, fructose doesn’t activate the body’s satiety signals that tell you to stop eating. Compared to glucose, fructose has little impact on ghrelin, the appetite hormone that is supposed to decrease in response to a meal. Fructose also produces smaller increases in satiety hormones such as glucagon-like peptide-1 (GLP-1) and insulin that blunt hunger in response to a meal.

Fructose has negative effects on the most powerful of metabolic organs, the liver: It increases fat storing in a way that is similar to alcohol, bypassing glycolysis and increasing fatty acid synthesis. This leads to fat being deposited in the liver, which can lead to liver disease and diabetes.

Is Sugar Addictive?

Studies of brain activity in response to sugar intake show that it alters our brain’s reward system, which drives overeating. This is the same process that is thought to underlie the tolerance associated with addiction. Most studies have been done on animals: Rats with intermittent access to sugar showed symptoms of bingeing, withdrawal, and craving in the same way that drug addicts do. Another study showed that intense sweetness surpasses the brain reward signals of cocaine, even for rats that were already dependent on cocaine.

Interestingly, combining fat with sugar may be less addictive than sugar alone. Animal studies show that rats who binged on a fat-sweet diet gained weight but did not display the same withdrawal effects as the sugar-addicted rats. Fat intake may protect against opiate-like withdrawal symptoms associated with excessive sugar consumption.

How Sugar Impacts The Brain & Memory

Because sugar changes the architecture of your brain, it harms memory and cognitive function. Some research shows that higher carbohydrate intake predicts the risk of cognitive impairment and dementia in the elderly. In school children, carbohydrate intake was negatively associated with nonverbal intelligence tests.

The theory goes that sugar damages blood vessels in the brain, which causes inflammation in the brain, leading to memory difficulties. The brain actually begins to shrink and production of a protective brain chemical known as BDNF that is essential for new memory formation and learning is reduced.

Scientists suggest the keto diet as the quickest solution to solving cognitive decline from sugar because it switches the brain’s fuel source from glucose to ketones. However, following a more balanced diet has also been shown to reverse memory decline if it radically reduces sugar intake. Substituting complex carbohydrates for sugar is a good place to start for people interested in getting off sugar.

Complex carbohydrates are more filling than sugars because their consumption leads the gut bacteria to produce short-chain fatty acids, which can increase the release of hormones that increase satiety, thus reducing food seeking behavior. Short-chain fatty acids inhibit fat storage and have anti-diabetic effects. They also reduce inflammation, and their consumption is a tool for reducing body fat.

Take Aways

If you feel you can’t stop eating foods that contain sugar, there’s a good reason! Sugar changes the pathways in your brain.

Foods containing fructose may be most addictive due to how they impact the brain’s reward system.

Foods that contain natural sugars, including fruit, beans, and whole grains don’t convey the same negative health effects as added sugar, in part because the proportion of calories from sugar is significantly less, and partly because of the other nutrients and fiber contained in these complex carbohydrates.

High sugar diets can lead to cognitive decline and problems with learning and memory. Reducing sugar and high-carb foods can reverse the negative changes.

A very low-carb keto diet is one solution if you feel like you are addicted to sugar, but a more manageable option may be to start by replacing sugar with complex carbs, such as fruit, vegetables, beans, and whole grains. This will allow you to get some of the benefits of removing added sugar without having to go through the adaptation process required to make keto successful.