Having sugar on our mind is one thing, but metabolizing sugar in our brain is a little less sweet. In research published in the Frontiers in Aging Neuroscience (a medical journal), scientists found an overactivation of fructose in the brain may lead to Alzheimer’s disease.
A team of neuroscientists, neurologists, and experts on fructose metabolism conducted the research. The findings not only point to the link between cognitive decline and excess sugar, but it also helps explain the link between Alzheimer’s and metabolic health .
What is Alzheimer’s disease?
Alzheimer’s disease is the most prevalent form of dementia and results in progressive loss of brain cells (neurons) and the junctions between those brain cells (synapses). This leads to cognitive decline, which worsens over time. Memory and learning are affected by the disease as an early sign, with more long-term memories being affected as the disease advances.
Though all types of dementia cause cognitive decline, Alzheimer’s disease, in particular, is characterized by the presence of 2 abnormal structures in the brain: neurofibrillary tangles and beta-amyloid plaques.
Accumulation of beta-amyloid plaques is worsened by particular genes, like ApoE4, which aggravates the risk of acquiring Alzheimer’s at an earlier age.
Removal of beta-amyloid has long been a focus of Alzheimer’s studies but has yielded no positive results. It is believed that this is due to the plaques, which are merely a symptom, so their removal is not useful unless the root causes of the disease are addressed.
[Also Read: Tips to Reduce the Risk of Alzheimer’s]
Glucose and insulin in Alzheimer’s disease
There are several factors at play in Alzheimer’s disease, and multiple factors can contribute to varying degrees in several individuals. This is one of the primary reasons Alzheimer’s is tough to treat .
In his book ‘The End of Alzheimer’ s,’ Dr. Dale Bredesen mentions that thirty-six triggering factors have been identified so far, and more are likely to follow. High glucose and high insulin are two of the most critical risk factors for Alzheimer’s disease, labeling one of the subtypes of Alzheimer’s as ‘glucotoxic’.
[Also Read: 5 Supplements for Glucose Support]
So how is blood glucose and insulin involved?
Firstly, having chronically high blood glucose levels can cause increased production of AGEs (advanced glycation end-products), which are lipids and proteins that have been destroyed by bonding to sugar. HbA1c is a
test of how much glucose is bonded to the hemoglobin of our RBC (red blood cells), and so is a measure of how many advanced glycation end-products are being produced in the blood. AGEs damage the brain in multiple ways by oxidative stress, promoting inflammation, and direct harm to our brain’s blood vessels .
Then, after insulin has done its job allowing glucose to enter cells, it is degraded by the rightly named IDE (‘insulin-degrading enzyme’). However, ‘insulin-degrading enzyme’ also degrades amyloid in our brain when it is not engaged in working on insulin.
The more insulin that is released into our blood, and the more often this happens, the less spare time ‘insulin-degrading enzyme’ has to remove amyloid from the brain. This means that taking sugar and refined carbohydrates often, particularly before bedtime when the brain does its housekeeping, may be contributing to Alzheimer’s disease in the long term by allowing amyloid to accumulate in the brain at a quicker rate .
Thirdly, in addition to its fat storage and glucose metabolism roles, insulin is a vital survival signal for neurons. When a person becomes insulin resistant by having inappropriately raised levels in the long-term, insulin no longer performs this role as potently.
This means that, apart from contributing to type 2 diabetes and metabolic syndrome, insulin resistance also contributes to the neuronal death seen in Alzheimer’s.
Sugar and Alzheimer’s
Some background: What exactly is “fructose metabolism”?
There are 2 common types of sugars: glucose and fructose.
Glucose is a kind of simple sugar that’s less sweet than fructose. When it travels to our bloodstream, it becomes what we commonly know of as blood sugar.
Fructose is a natural sugar commonly present in fruit juices, fruit, and honey. But it also makes up half of most table sugars, meaning it can be present in sodas, processed foods, baked goods, and high-fructose corn syrup—pretty much anything with added sugars.
A 2017 Yale research found that when individuals have elevated blood sugar levels for hours at a time, the brain begins to overproduce fructose. This mechanism is known as fructose metabolism and is common in type 2 diabetics.
Sugar: a metabolic poison?
So, high insulin and blood glucose levels can increase the risk of developing Alzheimer’s disease, but what changes can we make to our diet to fight this?
Of the 3 macronutrients, protein, carbohydrate, and fat, carbs have the most considerable effect on insulin response, with fat’s effect being almost non-existent and protein’s effect being moderate.
Not all carbohydrates are equal in causing an insulin response either; refined carbs (such as those in pastries, white bread, and other processed foods) are rapidly absorbed and cause a faster, more massive insulin response than the complex, natural carbs found in green vegetables.
In particular, sugar causes a very rapid insulin response and is added to most of the packaged foods we buy in the grocery market, from cereal bars to peanut butter and even bread.
A diet that is dense in refined carbohydrates and sugar is one that keeps on stimulating high insulin levels, generating high blood glucose, and provoking insulin resistance. This situation of metabolic dysfunction is what leads to Alzheimer’s disease.
Moreover, a diet low in sugar allows for better insulin sensitivity, meaning insulin can adequately perform its jobs. As sugar is the primary dietary driver of metabolic issues, it is arguably the most crucial thing to cut down on to prevent any disease with a metabolic component, including Alzheimer’s.
How does this impact Alzheimer’s risk?
When fructose metabolism happens due to excessive sugar intake, the brain goes into overdrive. The neural glycolysis process uses up necessary cerebral energy, making brain neurons less functional or viable over time.
Alzheimer’s disease is a modern disease driven by dietary lifestyle changes in which fructose can disrupt neuronal function and cerebral metabolism.
The study indicates overconsumption of fructose can spike fructose metabolism in our brain. The process finally takes energy away from other, more vital brain functions. Over time, this may cause Alzheimer’s disease—though more study needs to be done to conclude the theory.
By outlining persistent evidence, they hope to inspire researchers to continue exploring the relationship between Alzheimer’s disease and fructose in the brain. New treatments focused on inhibiting intracerebral fructose metabolism can offer a novel way to treat and prevent this disease.
In the meantime? Cutting back on sugar (sorry, sweet. tooths) may be one way to stave off these unnecessary neurodegenerative effects. Other lifestyle habits, like staying positive, regular exercise, and even drinking coffee, can also help support the brain.