You Are What You Eat : Alzheimer’s and Diabetes Edition A review of the effect of high fat and sugar diets on cognitive decline. Michelle Ha
Is there a relationship between a high fat diet, insulin resistance within the brain, and cognitive impairment? The aim of a 2017 study sought to determine whether a fatty diet, able to induce insulin sensitivity, has the ability to alter brain signalling pathways impacting cognitive functions. High fat diets have been observed to induce obesity, and obesity is often associated with insulin resistance and dementia. It is likely obesity and insulin resistance have some sort of association since approximately 85% of patients with type 2 diabetes mellitus are also obese (Kang et al., 2016). Furthermore, prior studies have observed that early stage Alzheimer’s patients tend to also show an impairment in insulin signalling (Ferreira et al., 2018). One of the most prevalent forms of dementia is Alzheimer’s disease, and is characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain. Kang’s study analyzed the effect of insulin induced changes in protein expression relating to cognitive impairment, and whether a high fat diet played a role. It was ultimately concluded that the mice given the high fat and sugar diet showed a statistically significant increase in obesity, lower insulin insulin sensitivity and glucose tolerance, and higher fasting insulin levels compared to the control group. Interestingly, impaired glucose uptake and insulin resistance was also seen in the brain. The researchers concluded that high fat diets cause inflammatory and stress responses which lead to the dysregulation of amyloid-β production and clearance rates, the formation of neurofibrillary tangles, and decreased synaptic plasticity within the brain. Furthermore, insulin resistance is a major pathological feature in patients with Type 2 Diabetes Mellitus, and could also be involved in Alzheimer’s since 80% of patients with Alzheimer’s are also diagnosed with type 2 diabetes, or at the very least, an impaired resting level of glucose (Kothari et al., 2017).
Key words: western diet, obesity, insulin resistance, Alzheimer’s disease.
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