How Sugar Affects The Brain

How Sugar Affects The Brain Graphic © herbshealthhappiness.com Background image: Pixabay (PD)

From refined sugars in confectionery to naturally occurring sugars in honey or fruits, sugar comes in many different forms—and it’s everywhere. But while your body needs sugar (glucose, to be precise) to run, you might want to rethink your decision the next time you reach out for a treat to satisfy your sweet tooth: According to Dr. Nicole Avena, a neuroscientist specializing in nutrition and addiction, too much sugar may adversely affect your brain.

Your Brain on Sugar – A Bitter-Sweet Relationship

Understanding the Brain’s Response to Sugar: When you drink soda, take a bite of your favorite chocolate, or consume anything sugary, sweet-taste receptors on your tongue are activated. This sends a signal to a region of your brain responsible for processing sensory information. The stimulus also triggers your brain’s reward system.

As the name implies, the “reward response” is activated in response to stimuli like sex, food, or addictive substances. When you consume sugar, dopamine—a neurotransmitter that influences your pleasure-seeking incentives—is released to potentially reinforce the behavior by answering the question, “Should I do that again?”

Some researchers believe that the release of the “feel-good chemical” dopamine in response to sweet taste is an evolutionary adaptation. ^[1] Seeking high-energy foods prevented starvation and helped our ancestors meet their energy needs at a time when sugar was rare.

Dr. Avena notes that sugar’s influence on the brain’s reward system differs from other foods. Typically, dopamine is only released in response to new foods (i.e., tasting something for the first time). This helps you pay attention to a varied diet. The dopamine response goes away the next time you taste the “new” food. However, the response is different when sugar is involved.

Dopamine is released every time you eat sugar—not just the first time. As a result, you continue craving more sugar since you’re feeling the reward with each bite of dessert and every slurp of juice.

Coincidentally, this dopamine response is similar to what happens to your brain when you take addictive drugs.

The relentless attraction to sugar due to how it affects the brain explains why people get hooked on sweet treats and sugary foods. While this trait may have given our ancestors an evolutionary leg-up, sugar is not rare today. It’s readily available in many foods—from obvious sources like candy to sneaky ones like peanut butter and sauces. And considering our mental hardwiring to reward sugar intake, the availability of sugar may lead to overconsumption.

What Happens When You Eat Too Much Sugar?

According to the Centers for Disease Control and Prevention (CDC), our total daily intake of added sugars should not exceed 10 teaspoons. ^[2] Yet, statistics estimate that Americans average around 19 teaspoons. This begs the question: “How does excessive sugar consumption affect the brain?”

Overeating can alter the brain’s reward system and create tolerance, whereby you need greater amounts of a substance to achieve the same level of reward. ^[3] As a result, excessive sugar intake has been linked to a form of addiction. ^[4] One study published in PloS One even suggested that the reward from the intense sweetness of sugar-rich diets may surpass that of cocaine. ^[5] The researchers concluded that stimulation from too much sugar “would generate a supranormal reward signal in the brain, with the potential to override self-control mechanisms and thus to lead to addiction.”

Research also points to a strong relationship between high sugar consumption and an increased risk of mental health problems and disruptions in memory function. ^[6][7] According to a study published in the New England Journal of Medicine, too much sugar may also cause inflammation, which is linked to neurodegenerative conditions like Alzheimer’s and dementia. ^[8] Additional research suggests that consuming a diet high in added sugars hinders the production of brain-derived neurotrophic factor (BDNF). ^[9] BDNF is a brain chemical that plays an important role in learning and the formation of new memory.

But while too much sugar can have negative effects on your brain, the opposite is also true. Too little glucose can impair your brain’s function, including cognitive processes, memory, and learning. This is because glucose (metabolized from sugar and carbs) is your brain’s primary source of energy. According to an article appearing in the Proceedings of the National Academy of Sciences, the brain accounts for 20% of your energy expenditure despite being only 2% of your body weight. ^[10]

Sugar and Cognitive Function

The relationship between sugar intake and cognitive function has been a subject of extensive research. Studies have explored how sugar, a major dietary component, influences behavior and mental performance. The consensus from scientific evidence indicates that while sugar plays a role in cognitive processes, its impact varies based on several factors, including age, type of sugar, and overall dietary patterns.

Sugar and Childhood Cognitive Performance: Research has shown that refined sugar intake does not significantly influence behavior or cognitive performance in children. While some children may exhibit idiosyncratic reactions or rare allergic syndromes leading to adverse responses, these instances are not widespread and require further investigation. The claim that sugar consumption leads to hyperactivity in children is not strongly supported by scientific evidence. ^[11]

Glucose and Memory Processing: Glucose, a simple sugar, has a clear role in the potentiation of memory processing. This suggests that glucose intake can enhance certain aspects of cognitive function, particularly memory. However, the clinical relevance of this role and the underlying mechanisms require further elucidation. ^[11]

Sugar’s Effect on Circadian Rhythms and Cognition: Dietary patterns, including those high in sugar, can impact circadian rhythms and consequently affect cognitive functions. Diets high in fat and sugar have been shown to alter the circadian distribution of meals in animal models, negatively impacting cognition and motivational aspects of behavior. These effects are mitigated when animals adhere to a standard temporal eating pattern, highlighting the interplay between diet, circadian rhythms, and cognitive health. ^[12]

The Link Between Sugar and Mood Disorders

Sugar consumption has been linked to mental health issues such as depression, anxiety, and mood swings.

Overview of Sugar’s Impact on Mental Health: The relationship between sugar consumption and mood disorders, including depression and anxiety, has been a subject of increasing interest in recent scientific research. Studies have explored how dietary patterns, particularly those high in sugar, influence mental health outcomes.

Maternal High-Sugar Diet and Offspring’s Mental Health: A 2023 study investigated the impact of maternal diets high in monosaccharides, specifically glucose and fructose, during pregnancy and lactation on the cognitive, locomotor, and emotional health of offspring rats. The study found that maternal diets high in these sugars led to anxiety-like behavior in adolescent and young adult offspring. Additionally, hyperactivity and depressive-like behavior were observed in male adolescent rats, with a significant enhancement in novelty-seeking behavior in young adult male rats. This research suggests that maternal sugar consumption can have long-lasting effects on the emotional and behavioral health of offspring. ^[13]

Dietary Patterns, Microbiota, and Mood Disorders: Another study reviewed the connections between diet quality, gastrointestinal microbiota, and mood disorders. It found that improving diet quality can positively affect mood. The consumption of fructooligosaccharides and galactooligosaccharides, at doses of 5g/day or more, improved anxiety and depression symptoms in participants. This study highlights the role of dietary components and the gastrointestinal microbiota in influencing mood disorders like depression, anxiety, and stress ^[14]

Sugar Addiction

Sugar addiction is a real phenomenon with substantial parallels to drug addiction, both in terms of brain neurochemistry and behavior. The development of sugar cravings and dependence is influenced by neurological pathways, genetic factors, and the body’s natural opioid system. Understanding the mechanisms of sugar addiction is crucial for addressing related health issues, including obesity and eating disorders.

Sugar addiction is a concept that has gained attention in recent years, with studies suggesting that sugar can produce symptoms similar to those of addictive substances. Animal studies have shown that the consumption of added sugars can lead to drug-like effects, including bingeing, craving, tolerance, withdrawal, cross-sensitization, cross-tolerance, cross-dependence, reward, and opioid effects. This suggests that sugar addiction may be a dependence on the natural endogenous opioids released upon sugar intake. ^[15]

Neurological Basis of Sugar Addiction: The neurological pathways involved in sugar addiction are similar to those in drug addiction, involving neural receptors, neurotransmitters, and hedonic regions in the brain. The release of endorphins and dopamine within the nucleus accumbens, triggered by sugar-rich foods or drinks, mirrors the effects of some drugs of abuse. This overlap between the neurobiological pathways of drug and sugar addiction indicates a shared basis in brain chemistry and behavior. ^[16]

Development of Sugar Cravings and Dependence: Sugar cravings and dependence develop through a complex interplay of neurological and psychological factors. The pleasurable response to sugar, mediated by the brain’s reward system, can lead to a cycle of cravings and dependence. Additionally, there is evidence of cross-sensitization between sugar addiction and narcotic dependence in some individuals, suggesting a common vulnerability to addictive behaviors. ^[16]

Genetic Factors in Sugar Addiction: Research has identified specific genetic markers that may underlie the sweet preference in alcohol- and drug-dependent individuals, as well as in biological children of paternal alcoholics. Common genetic markers have been found between alcohol dependence, bulimia, and obesity, such as the A1 allele gene and the dopamine 2 receptor gene. This indicates a genetic predisposition to sugar addiction in certain populations. ^[16]

Natural Sugars vs. Added Sugars

The distinction between natural sugars and added sugars is crucial in understanding their different health effects – because the health effects of natural sugars and added sugars are markedly different. While natural sugars in whole foods are part of a healthy diet, added sugars contribute to various health risks. Understanding these differences is crucial for making informed dietary choices and for public health recommendations. Natural sugars are found in whole foods like fruits, vegetables, and milk, whereas added sugars are incorporated into foods and beverages during processing or preparation.

Natural Sugars – Characteristics and Health Effects Natural sugars, such as those in fruits and vegetables, are intrinsic components of these foods. They are typically accompanied by fiber, vitamins, and minerals, contributing to their nutritional value. The slow digestion of these sugars due to the presence of fiber results in a gradual release of glucose into the bloodstream, which helps maintain stable blood sugar levels. There is no reported evidence of adverse effects from the consumption of natural sugars in whole foods. ^[17]

Added Sugars – Characteristics and Health Risks: Added sugars, including monosaccharides like glucose and fructose and disaccharides like sucrose, are commonly added to processed foods and beverages. These sugars are rapidly absorbed into the bloodstream, leading to spikes in blood sugar levels. High intake of added sugars is associated with various health issues, including obesity, type-2 diabetes, cardiovascular disease, and dental caries. The World Health Organization (WHO) recommends limiting free sugar intake to less than 10% of total energy intake, emphasizing that a further reduction to 5% would provide additional health benefits. ^[17]

Metabolic Differences: The metabolism of natural and added sugars differs significantly. While natural sugars are slowly metabolized due to the presence of fiber and other nutrients, added sugars are quickly absorbed and metabolized, leading to rapid increases in blood sugar and insulin levels. This can contribute to insulin resistance and other metabolic disorders.

Impact on Health: The consumption of foods high in added sugars is linked to an increased risk of obesity, heart disease, and dental problems. In contrast, the consumption of fruits and vegetables, which contain natural sugars, is associated with a reduced risk of these conditions. The quality of sugar-containing foods should be assessed based on their overall nutritional content, not just their sugar content.

The Role of Sugar in Brain Inflammation and Oxidative Stress

Recent scientific research has increasingly focused on the impact of high sugar diets on brain health, particularly concerning inflammation and oxidative stress. These studies have explored how excessive sugar intake can lead to detrimental changes in brain function and structure.

Sugar and Brain Inflammation: High sugar diets have been linked to increased inflammation in the brain. This inflammation is primarily driven by the overproduction of free fatty acids and systemic inflammation, which can reach the brain and initiate local inflammatory responses. These responses are often mediated by microglial cells, the primary immune cells in the brain. Chronic inflammation in the brain can contribute to the development of neurodegenerative diseases and cognitive impairments. ^[18]

Sugar-Induced Oxidative Stress: Oxidative stress in the brain, caused by an imbalance between the production of reactive oxygen species (ROS) and the body’s ability to detoxify these reactive intermediates, is another consequence of high sugar diets. Excessive sugar intake can lead to increased ROS production, which in turn causes oxidative damage to critical biomolecules, including DNA, proteins, and lipids. This oxidative damage is a key factor in the pathogenesis of various neurodegenerative diseases. ^[18]

Mechanisms of Sugar-Induced Brain Changes: The mechanisms by which high sugar diets induce these changes in the brain involve complex interactions between dietary components, metabolic pathways, and the body’s immune response. For instance, diets high in sugar can alter the gut microbiota, leading to increased intestinal permeability and systemic inflammation. This systemic inflammation can then affect the brain, contributing to neuroinflammation and oxidative stress. ^[18]

Impact on Cognitive Function: The impact of sugar-induced inflammation and oxidative stress on cognitive function is significant. Studies have shown that diets high in sugar can impair cognitive abilities, including memory and learning. This is particularly concerning given the increasing prevalence of high sugar diets in modern society. ^[18]