Science has long established the myriads of health problems associated with the regular overconsumption of food high in carbohydrates. In fact, several studies have linked a diet high in carbohydrates with accelerated aging and the emergence of age-related diseases.
One study concluded that a diet that restricts the intake of carbohydrates could regulate the functions of about 900 genes responsible for aging and memory formation.
Take note that carbohydrates are one of the main types of macronutrients and are a common source of energy in living organisms. Known examples of carbohydrates include sugar, starch, and cellulose.
Because sugar is a commonly consumed form of carbohydrates, in addition to the fact that the prolonged overconsumption of carbohydrates-rich food correlates with aging and age-related diseases, other studies have also explored the specific negative effects of high sugar consumption on brain function and structure, as well as its addiction-forming tendency.
How Sugar Affects The Brain: An Examination of Notable Studies
Effects of High Sugar Consumption on Brain Function
Researchers Tem M. Hsu et al. studied the impact of a high sugar diet on the brain function of adolescent mice. One group of mice freely fed with high-fructose corn syrup or HFCS demonstrated impairment in hippocampal-dependent spatial learning and memory. Another group of rats fed with sucrose also demonstrated moderate impairment in learning.
They also detected neuroinflammation in the hippocampus of the mice fed with HFCS. Take note that the hippocampus is a part of the temporal lobe located deep within the brain that controls learning and memory formation.
Hsu et al. explained that the brain is vulnerable to dietary influences during critical periods of development. The mouse experiment served as a model for understanding the negative effects of high HFCS consumption in the adolescent human brain. Note that the amount of HFCS fed in the rats had concentrations comparable to popular sugar-sweetened beverages.
An earlier study involving rats fed with fructose by Rahul Agrawal and Fernando Gomez-Padilla revealed similar results. Their research revealed that high sugar consumption impaired cognitive abilities and disrupted insulin signaling by engaging molecules associated with energy metabolism and synaptic plasticity.
However, this same study by Agrawal and Gomez-Padilla mentioned that the negative effects of high sugar consumption in the brain, particularly in memory, can be partially counteracted by daily supplementation of Omega-3 fatty acid.
It is also worth mentioning that diabetes is also a risk factor for depression. In their systematic review of the literature, researchers Tapash Roy and Cathy E. Lloyd found that the prevalence rate of depression is more than three times higher in people with type 1 diabetes and nearly twice as high in people with type 2 diabetes compared to those without.
The link between diabetes and depression is commonly attributed to increased stress from managing a chronic and complex disease. However, experts are starting to look at the link between high sugar levels in the body and depression.
Effects of High Sugar Consumption on Brain Structure
Individuals whose blood sugar is on the high end of the normal range may be at greater risk of similar brain shrinkage observed in aging and diseases such as dementia. Take note that several studies have also established a link between type 2 diabetes and brain shrinkage.
Researchers N. Cherbuin et al. investigated whether non-diabetic individuals with blood sugar on the high end of the normal range experience similar brain shrinkage. Their study involved 249 people between the ages of 60 to 64 who had blood sugar in the normal range. They subjected these individuals to brain scans at the start of the study and again about four years after.
The results of the scans suggested that those with higher fasting blood sugar levels within the normal range and below 110 mg/dL were more likely to have a loss of brain volume in the areas of the hippocampus and the amygdala—areas that are involved in memory and cognitive skills—than those with lower blood sugar levels. This loss of brain volume is specifically referred to as hippocampal atrophy.
After controlling for age, high blood pressure, smoking, alcohol use, and other factors, the researchers found that blood sugar on the high end of normal accounted for six to 10 percent of the brain shrinkage.
Nonetheless, the study suggests that even non-diabetic individuals whose blood sugar level is at the high end of the normal range are susceptible to brain shrinkage observed in people with diabetes or those with dementia and other age-related brain impairments.
Another study by Mortby and Cherbuin et al. that involved analyzing the brains of 210 cognitively healthy individuals between the ages of 68 and 73 revealed similar but results. Results of the analyses suggest that higher blood sugar levels in the normal range were associated with lower grey and white matter regional volumes in the frontal cortices, particularly the middle frontal gyrus, inferior frontal gyrus, and precentral gyrus. These identified cerebral regions were also associated with poorer cognitive performance.
Then there is the link between a high-carbohydrate diet and the development of Alzheimer’s disease. A study by Stephanie Seneff, Glyn Wainwright, and Luca Mascitelli revealed that neurons become severely damaged due to chronic exposure to glucose and oxidizing agents. Due to impaired functions, these neurons enter a state of apoptosis or programmed cell death.
The Studies In A Nutshell: Sugar and the Brain
Based on the discussions above, a diet high in sugar leads to damage to the brain. From impairment in hippocampal-dependent spatial learning and memory, and neuroinflammation in the hippocampus, to hippocampal atrophy and neural apoptosis, the referenced studies illustrate damages due to high sugar consumption transpiring at the cellular and molecular levels.
FURTHER READINGS AND REFERENCES
- Agrawal, R. and Gomez-Pinilla, F. 2012. “Metabolic Syndrome in the Brain: Deficiency in Omega-3 Fatty Acid Exacerbates Dysfunctions in Insulin Receptor Signaling and Cognition.” The Journal of Physiology. 590(10): 2485:2499. DOI: 1113/jphysiol.2012.230078
- Cherbuin, N., Sachdev, P., and Anstey, K. J. 2012. “Higher Normal Fasting Plasma Glucose is Associated with Hippocampal Atrophy: The PATH Study.” Neurology. 79(1): 1019-1026. DOI: 1212/wnl.0b013e31826846de
- Mortby, M. E., Janke, A. L., Anstey, K. J., Sachdev, P. S., and Cherbuin, N. 2013. “High “Normal” Blood Glucose Is Associated with Decreased Brain Volume and Cognitive Performance in the 60s: The PATH Through Life Study.” PLOS ONE. 8(9): e73697. DOI: 1371/journal.pone.0073697
- Hsu, T. M., Konanur, V. R., Taing, L., Usui, R., Kayser, B. D., Goran, M. I., and Kanoski, S. E. 2014. “Effects of Sucrose and High Fructose Corn Syrup Consumption on Spatial Memory Function and Hippocampal Neuroinflammation in Adolescent Rats.” Hippocampus. 25(2): 227-239. DOI: 1002/hipo.22368
- Roy, T. and Lloyd, C. E. 2012. “Epidemiology of Depression and Diabetes: A Systematic Review.” Journal of Affective Disorders. 142: S8-S21. DOI: 1016/s0165-0327(12)70004-6
- Seneff, S., Wainwright, G., and Mascitelli, L. 2011. “Nutrition and Alzheimer’s Disease: The Detrimental Role of a High Carbohydrate Diet. European Journal of Internal Medicine. 22(2): 134-140. DOI: 1016/j.ejim.2010.12.017