Science has long established the myriads of health problems associated with regular overconsumption of food high in carbohydrates. Several studies have in fact linked a diet high in carbohydrates with accelerated aging and the emergence of age-related diseases.
One study concluded that a diet that restricts 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 and because a regular overconsumption of carb-rich food correlates with aging and age-related disease, other studies have also explored the specific negative effects of high sugar consumption in brain function and structure.
Effects of high sugar consumption in brain function
Researchers Tem M. Hsu et al studied the impact of high sugar diet in the brain function of adolescent mice. One group of mice freely fed with of high-fructose corn syrup or HFCS demonstrated impairment in hippocampal-dependent spatial learning and memory. Another group of rat fed with sucrose also demonstrated moderate impairment in learning.
They also detected neuro-inflammation in the hippocampus of the rats fed with HFCS. Take note that the hippocampus is a part of the temporal lobe located deep within the brain that controls memory formation.
The researchers reminded that the brain is vulnerable to dietary influences during critical periods of development—including adolescence. The rat experiment served as a model for understanding the negative effects of high HFCS consumption in adolescent human brain. In fact, 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. They concluded that high sugar consumption impaired cognitive abilities and disrupted insulin signalling by engaging molecules associated with energy metabolism and synaptic plasticity.
The same study by Agrawal and Gomez-Padilla however mentioned that the negative effects of high sugar consumption in brain, particularly in memory, can be partially counteracted by daily supplementation of Omega-3 fatty acid.
Diabetes is also a risk factor for depression. In their systematic review of literatures, 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 an 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 in brain structure
Individuals whose blood sugar is on the high end of 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 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 under 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 normal range and bellow 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.
The study nonetheless suggest that even non-diabetic individuals whose blood sugar level is at the high end of the normal range is susceptible to brain shrinkage observe in people with diabetes or those with dementia and other age-related brain impairments.
Another study by Cherbuin et al that involved analysing the brains of 210 cognitively health individuals between the ages of 68 and 73 revealed similar but results. Results of the analyses suggest that higher blood sugar level in the normal range were associated with lower grey and white matter regional volumes in the frontal cortices, particularly 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 Wain Wirght, and Luca Mascitelli revealed that neurons become severely damaged due to chronic exposure to glucose and oxidising agents. Due to impaired functions, these neurons enter a state of apoptosis or a programmed cell death.
In summary, a diet high in sugar leads to damages in the brain. From impairment in hippocampal-dependent spatial learning and memory, and neuro-inflammation 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 details of the study of Hsu et al are in the article “Effects of Sucrose and High Fructose Corn Syrup Consumption on Spatial Memory Function and Hippocampal Neuroinflammation in Adolescent Rats” published in October 2014 in the journal Hippocampus. Details of the study of Rahul and Gomez-Padilla are in the article “Metabolic Syndrome in the Brain: Deficiency in Omega-3 Fatty Acid Exacerbates Dysfunctions in Insulin Receptor Signalling and Cognition” published in ay 2012 in The Journal of Physiology.
Further details of the study of Cherbuin et al are in the article “High Normal Fasting Plasma Glucose is Associated with Hippocampal Atrophy” published in 2012 in the journal Neurology. Details of the study of Cherbuin et al are in the article “High ‘Normal’ Blood Glucose is Associated with Decreased Brain Volume and Cognitive Performance in the 60s: The PATH Through Life Study” published in September 2013 in the journal PLOS One.
Further details of the study of Roy and Lloyd are in the article “Epidemiology of Depression and Diabetes: A Systematic Review” published in October 2012 in the Journal of Affective Disorders. Further details of the study of Seneff et al are in the article “Nutrition and Alzheimer’s disease: The detrimental role of a high carbohydrate diet” published in 2013 in the journal European Journal of Internal Medicine.