How sugar impairs MEMORY and causes COGNITIVE decline

In the world of low-carb diets, sugar is being demonized. I can’t help but wonder exactly how bad sugar is and why?

Also because I just got done inhaling two cookies.

Overeating, poor memory, learning disorders, depression – all these are linked to overconsumption of sugar. According to the U.S Department of Agriculture, the average American consumes 156 lbs of added sugar per year. Brain cells require two times the energy required by all the other cells in our body.

In neuroscience, we call food a “natural reward”, food is essential for our survival and also pleasurable. We have a reward system in place called mesolimbic pathway, which deciphers these natural rewards for us by using the neurotransmitter dopamine to signal a part of the brain called nucleus accumbens. The connection between the nucleus accumbens and our prefrontal cortex decides whether we should take another bite of that cookie or not. The prefrontal cortex also releases hormones to tell our body “Hey, that cookie is delicious. I’m gonna remember that for the future”. Our body is trained by our ancestors to give preference to sweet food over others because they’re high in carbohydrates, which equals energy. Also, sweet indicated fruits were ripe and good to eat, while bitter or sour meant poison.

Not all foods are created equal.

That was then, this is now. Glucose is the primary fuel for the human brain, but what happens when we expose it to excessive added sugars?

Diabetes and Alzheimer’s Disease

Research done in 2002 by Dr. Molteni suggests that a diet high in sugar reduces the production of a brain chemical called BDNF – brain-derived neurotrophic factor. Without BDNF, neither can we form new memories, nor learn new information. This is why diabetics have lower levels of BDNF and as the BDNF reduces, the sugar metabolism worsens. BDNF is also directly linked to depression and dementia. In a study conducted in 2009 by Dr. Z. Kroner, concluded that diabetic patients are at a higher risk for Alzheimer’s disease due to Advanced glycation end products (AGE’s), which are proteins or fats that become glycated after exposure to sugars accumulate in neurofibrillary tangles and amyloid plaques in the brain.

Cognitive impairment


Elevated blood sugars damage blood vessels causing progressive decline in brain function. Studies conducted on subjects living with diabetes indicated deficits in learning, memory, motor speed and other cognitive functions. Frequent exposure to high levels of sugar lowers brain capacity, as higher HbA1C (hemoglobin A1c – used to measure plasma glucose concentration) levels is associated with greater degree of brain shrinkage. According to a 2011 study, there was a positive correlation between higher sugar intake and lower cognitive function, which was measured by giving participants various cognitive tasks.

Sugar not only has a long term impact on our brain, but also short-term effects right after eating sugar called the hyperglycemic state, slowing down cognitive function resulting in attention deficit and memory. It compromises the brain’s ability to process emotions.



Going back to the reward system, our brain processes high-glycemic foods by activating regions of the brain associated with reward response and intense feelings of hunger compared to low-glycemic foods. This clearly suggests that foods that causes higher elevation in glucose produces a greater addictive drive in the brain, impairing self-control.

As we can see, refined sugar has a large impact on our brain.

How to:

1. Substitute refined sugar with natural sugar
2. Cut out refined sugar from foods and drinks completely, it may be hard to go cold turkey all at once, but it’s all worth it.
3. Introduce high intensity interval training or any other type of aerobic exercise in your schedule (Please read – Science of BRAIN growth  and REGENERATION with workout or listen to podcast 25)




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