While Halloween may look a little different than it normally does this year, the one constant is that there will undoubtedly be an influx of available candy in every store, office, and socially-distant gathering. While any food eaten in moderation can tie into an overall healthy lifestyle, Halloween candy is an excellent example of something that we can all relate to overindulging in. Aside from the obvious tummy ache and sugar crash, most of us assume that there isn’t much harm in overdoing it from time to time.
If having a bit of extra Halloween candy is truly a once-every-year experience, then it likely isn’t going to cause you long-term problems. However, when overindulging in sweets or other carbohydrates becomes a pattern, your blood sugar becomes chronically elevated (also known as hyperglycemic). Hyperglycemia, when severe enough, is called diabetes, and both can cause a host of problems, including neurodegeneration, memory decline, Alzheimer’s, Parkinson’s disease, mood disorders, and more.
How can this be? And what can cause your blood sugar levels to rise?
Eating a diet high in sugar, simple carbs, and saturated fat can increase your normal blood sugar levels. Even consuming unbalanced meals that are too low in lean protein or healthy fats and carbs, or portion sizes that are too large can cause unhealthy spikes. Factors outside of your diet like stress, illness, dehydration, and lost sleep can also affect your blood sugar levels or your body’s ability to use insulin (1, 2).
But how does your blood glucose level affect your brain?
At the very least, chronic high-sugar diets often cause inflammation in the brain, which can affect overall brain function, especially memory (3). It can also affect something called BDNF (brain-derived neurotrophic factor), which is a growth factor that supports neuron survival and regeneration. Over time, a diet high in saturated fat and sugar (and the resulting elevated blood sugar levels) can reduce BDNF levels, synaptic plasticity, and other proteins that help regulate cognition and mood (4). Meaning: hyperglycemia can actually alter the brain’s structure and resulting function!
What do these brain changes lead to?
Any physical changes to your brain’s structure will lead to noticeable effects in your life. The reduced BDNF levels and synaptic plasticity mentioned above can lead to memory decline. Compounding this effect is the fact that chronic hyperglycemia, especially in those who have long-term diabetes, has been linked to lessened neural connectivity in the brain. This can lead to brain atrophy, and in some cases, small-vessel disease. Atrophy and small vessel disease both restrict blood flow to the brain, increasing the risk of cognitive decline and vascular dementia (5).
Are there other links between memory decline, Alzheimer’s, and elevated blood sugar?
While many factors can cause memory decline, dementia, and Alzheimer’s, studies have found that those who have Alzheimer’s often have problems metabolizing glucose properly, meaning their insulin response is not functioning properly (6). Because insulin helps regulate brain cell survival and plasticity in the areas that are most prone to Alzheimer’s-causing neurodegeneration, it is no wonder that chronically raised blood glucose levels would seriously endanger the brain’s structure and function (6).
The increase in Alzheimer’s and the simultaneous increase in diabetes (with no known genetic predisposition) point further to this link. People with diabetes have higher rates of cognitive impairment and, unfortunately, at least twice the risk of developing Alzheimer’s than non-diabetics do (6). Other types of insulin-related disorders including pre-diabetes, metabolic syndrome, high fat diet-induced obesity, and non-alcoholic fatty liver disease are all linked to Alzheimer’s and other forms of cognitive decline (6, 7). Some of these disorders, especially type 2 diabetes mellitus (T2DM), are considered risk factors because they lower the threshold for the development of dementia (7). Interestingly, the symptoms of Alzheimer’s such as dysregulated lipid and carbohydrate metabolism, inflammation, energy imbalance, and cell stress and death are all present in insulin-resistant diseases as well. This could be because Alzheimer’s, diabetes, and inflammation are all linked within certain gene clusters (6). One study even suggests that Alzheimer’s should be regarded as a brain form of diabetes (6, 7).