Sugar is a valuable nutrient source for your body — and your brain is the body’s main consumer of glucose, metabolizing over a fifth of all glucose-derived energy. However, a popular saying remains poignant for our discussion today: “Too much of a good thing is a bad thing.” That’s because the obesity epidemic continues to plague the U.S. today: rising sugar consumption among adolescents increases the risk of obesity and drives health conditions such as hypertension. Moreover, eating too much sugar has been linked with impaired neurological development and negative emotions associated with mental illness.

In this article, we will provide an overview of how the brain develops in adolescent years, relate how sugar consumption is linked with cognitive impairments and mental health disorders, and offer up ways in which adolescents can satiate their sweet tooth without consuming too much sugar.

Critical processes underlying brain development in adolescents

The adolescent years represent the most important time for a child’s development. The central nervous system (CNS) – comprising the brain and the spinal cord – matures during this time, and the maturation process features changes to the neurons in the brain that enable the body to react to its surroundings:

• Plasticity: This term refers to the brain’s ability to alter its structure and function over time. Dendrites, specialized cells that receive signals from neurons, contribute to brain plasticity by changing the sets of connections they make with other neurons. If you are a parent, you are also well aware of the many new experiences an adolescent will have as they grow up. These experiences can shape how your child’s brain develops as they age.
  
• Brain maturation: During puberty, the human brain undergoes substantial growth. The brain constantly rewires itself until the person is 25 years old. A person’s gray matter — the part of the brain that facilitates muscle movement and sensual perception —  increases in surface area and reduces thickness as the maturation process occurs. That said, the brain doesn’t just increase the amount of grey matter; the teenage brain also prunes existing grey matter to improve the efficiency of neural connections.
  
• Brain usage: Before the teenage brain fully matures, different parts of it tend to be employed more often than in an adult brain. For one, the prefrontal cortex, the part of the brain that mediates planning, judgment, and reasoning, continues to develop during the adolescent years. As a result, teenage brains tend to employ the amygdala more, the part of the brain that mediates emotional behavior and motivation. When combined with hormonal shifts in the activity of the hypothalamic-pituitary-adrenal axis, an adolescent will become highly vulnerable to new, sudden environmental shifts. 

Despite the advances in what the scientific community has learned about brain development, many questions remain. For one, when examining the brain during adolescence, various study designs are plagued with methodological issues that can lead to data inconsistencies. Scientists also need to better study how one’s habits impact brain development.

Sugar consumption and brain development

Sugars provide a consistent energy supply for your cells. While sugars occur naturally in healthy foods such as fruits and vegetables, they are also present as added sugars in processed foods and sweeteners. As the prevalence of obesity among adolescents continues to rise with increased sugar consumption, the lack of research detailing the impacts of eating sugar on teenage brain development is concerning. Nevertheless, there is research being done to investigate the relationship between sugar consumption and brain development in rat and mouse models.

• A 2015 study determined that young rats who consumed high levels of sucrose (10% sucrose solution) — a common sugary ingredient in soft drinks — were less able to use contextual information to respond appropriately and solve problems. Those same rats also struggled to perform recognition memory tasks, stemming from reduced neuronal activity in the hippocampus — the part of the brain that facilitates learning and memory — and in the prefrontal cortex.
  
• A 2013 study aimed to examine the effects of long-term sucrose consumption on cognition in adolescent rats. The rats that ate excess sucrose demonstrated impaired memory in a maze test, even up to six weeks after sucrose consumption. These effects may portend the long-term effects of sugar consumption among adolescents.
  
• Another 2015 study investigated the effects of excessive sugar consumption on cognitive function in rat models. The rats that fed on an 11% sucrose solution or a high-fructose corn syrup had reduced spatial learning and memory when performing a maze task. Follow-up research into brain physiology showed that an inflammatory state exists in the hippocampus, possibly contributing to its impaired function.
  
• Some of the impacts that sugar consumption has on brain development may be connected to the gut microbiome. In a 2021 study, alterations to the gut microbiome were observed in rats after they were fed a high-sugar diet. In particular, two members of the Parabacteroides genus, whose relative abundances increased among rats fed the high-sugar diet, were negatively correlated with memory-based functions. These changes were linked to the impaired function of the hippocampus.

Sugar and mental health

With the many impacts that sugar can have on brain development, it stands to reason that eating too much sugar can also have negative impacts on mental health. For one, we know that there are links between blood sugar levels and anxiety. Additionally, established research literature provides other correlations between sugar consumption and other mental health disorders.

• Addictive behaviors: Excess sugar consumption can induce behaviors akin to addiction toward an unhealthy diet featuring high fat and sugar ingestion. This behavior is mediated through a constant release of dopamine, as was observed in rat models.
  
• Anxiety and depression: A 2018 study examined the effects of unlimited sucrose consumption on the mental health of adolescent male rats. The rats that ate too much sucrose were less able to feel pleasure and more likely to experience anxiety-associated symptoms. A 2019 meta-analysis of 10 observational studies also determined that drinking the equivalent of 2 to 3 cola cans per day increased the risk of depression by 25%.
  
• Many of the effects on mental health observed among male rat models have been observed, as well, from a diet featuring consumption of significant quantities of “low-sugar sweeteners” (or “artificial sugar substitutes”) early in life. A 2022 study determined that eating low-calorie sweeteners early in life impacted hippocampal-dependent memory and sugar-motivated behaviors in rats. However, only three (saccharin, acesulfame potassium, and stevia) out of the dozens of available sugar substitutes were studied, and all three were lumped together statistically in the study design, suggesting that much more research is required before definitive conclusions should be drawn. Sugar alcohols (as distinguished from artificial sugars), such as sorbitol, were not studied.

Keeping your child healthy with less added sugar

Children are well known for having a sweet tooth. Sugar is a delicious additive to most foods, but its negative impacts on physical and mental health pose a substantial risk when too much is ingested. With that in mind, here are some suggestions to help keep your child healthy while still giving them chances to enjoy the desserts they eat.

• Stop drinking sugar-sweetened beverages: Many of the negative effects of sugar consumption observed through research were tested using sugar-sweetened beverages (known as SSBs). Similar kinds of drinks include soft drinks, sports drinks, and even fruit juice. (Learn more: What happens to your blood sugar after drinking soda?) Consider providing your child with low-fat milk, chocolate milk (without added sugars) and water instead of SSBs to help them obtain enough fluids during the day.
  
• Consider healthy dessert and snack options: There are many healthy dessert recipes all over the internet. Consider making a fruit basket that contains healthy, tasty fruits that are low in natural sugars (i.e., have a low Glycemic Index, or GI value). Also consider these keto-diet snacks, which aren’t processed with much added sugar but do contain other healthy ingredients that maximize your child’s gut health.
  
• Replace those added sugars: Eating high quantities of refined sugar is associated with worsening metabolic disease and exacerbated risks of mental health disorders. When making desserts or snacks, consider healthier natural sweeteners such as applesauce, dates, or even chocolates in moderation. Little by little, you’ll be helping your child head down the healthy dietary path epitomized by a plant-based or Mediterranean diet, both of which have been deemed healthier (both in terms of cardiometabolic and mental health outcomes) than our processed/sugary Western diet.
  

Key takeaways

Adolescence is the most important time for brain development. During these years, the brain undergoes considerable changes as it processes the many events and emotions that a child experiences while growing up. Clinical research points overwhelmingly to the fact that rising sugar consumption among adolescents is a huge problem in the U.S. because it increases the risk of metabolic and cardiovascular disorders. Furthermore, earlier-stage research indicates the likelihood that excessive sugar consumption during adolescence also triggers and/or exacerbates mental health issues. Therefore, adolescents would benefit greatly from adopting dietary habits that include much lower consumption of added sugars, and fortunately there are many healthier food and recipe alternatives that can still satisfy a sweet tooth.

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