WARNING!
This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.
By Dr. Mercola
Many people now associate elevated blood sugar levels with diabetes or even pre-diabetes, but new research has highlighted a little-known adverse effect of higher blood sugar levels that can impair your brain – even if your levels are technically still within a ‘normal’ range.
The study – an extremely important one considering the epidemic of people with out-of-control blood sugar metabolism – showed that lower blood sugar levels are associated with better brain function and may even help you avoid age-related declines in memory.
Higher ‘Normal’ Blood Sugar Levels Linked to Memory Loss
It’s already known that people with type 2 diabetes have an increased risk of developing cognitive impairment, including dementia. However, the new study involved people (with an average age of 63) who were free from diabetes and pre-diabetes (or impaired glucose intolerance).
Still, even among this group, those with higher blood sugar levels scored lower on memory tests.
For each 7-mmol/mol increase in HbA1c (a measure of damage caused by elevated blood glucose), participants recalled two fewer words on memory tests.1 Those with higher blood sugar levels also had lower volume of the hippocampus, a brain region essential for the faculty of memory. As one of the study’s authors said:
"Clinically, even if your blood sugar levels are 'normal,' lower blood sugar levels are better for your brain in the long run with regard to memory functions as well as memory-relevant brain structures like the hippocampus.
Scientifically, we were able to shed further light on the mechanisms mediating these effects. DTI-based (diffusion tensor imaging) measurements demonstrated that not only volume of the hippocampus, but also microstructural integrity is lower if blood sugar levels are higher."
They concluded that even if you don’t have type 2 diabetes or pre-diabetes, higher blood sugar levels appear to have a negative influence on cognition. Most likely, this effect has to do with disrupted insulin and leptin levels and signaling in the brain …
The Insulin Connection to Your Brain Health
Most adults have about one gallon of blood in their bodies and are quite surprised to learn that in that gallon, there is only one teaspoon of sugar! In other words, your body is designed to have just one teaspoon of sugar in your blood at all times -- if that. If your blood sugar level were to rise to one tablespoon of sugar you would run the risk of going into a hyperglycemic coma and even dying.
Your body works very hard to prevent this from happening by producing insulin to keep your blood sugar at the appropriate level. Any meal or snack high in grain and sugar carbohydrates typically generates a rapid rise in blood glucose.
To compensate for this your pancreas secretes insulin into your bloodstream, which lowers your blood sugar to keep you from dying. Insulin, however, is also very efficient at lowering your blood sugar by turning it into fat – so the more you secrete, the fatter you become.
Also, insulin quickly drops blood sugar levels, which threatens to cause your brain to go through an acute deficiency state; this vicious cycle often causes a roller coaster of intense cravings for more of the same endocrine disruptive carb rich foods.
Unfortunately, If you consume a diet consistently high in sugar and grains, your blood glucose levels will be correspondingly high and over time your body becomes "desensitized" to insulin and requires more and more of it to get the job done.
Eventually, you become insulin resistant, and then full-blown diabetic. But as the new study showed, health effects of this elevated blood sugar/insulin cycle begin to occur even before insulin resistance sets in.
Poor Diet Linked to Dementia, Including Alzheimer’s Disease
While insulin is usually associated with its role in keeping your blood sugar levels in a healthy range, it also plays a role in brain signaling. In one animal study, when researchers disrupted the proper signaling of insulin in the brain, they were able to induce many of the characteristic brain changes seen with Alzheimer's disease (disorientation, confusion, inability to learn and remember).2
It's becoming increasingly clear that the same pathological process that leads to insulin and leptin resistance and type 2 diabetes may also hold true for your brain.
As you over-indulge on sugar and grains, your brain becomes overwhelmed by the consistently high levels of insulin and eventually insulin and leptin levels and signaling becomes profoundly disrupted, leading to impairments in your thinking and memory abilities, and eventually causing permanent brain damage, among other health issues.
Research has even shown that higher glucose levels are associated with a higher perceived age;3 in other words, the higher your glucose levels, the older you’ll tend to look!
Get Your Fasting Insulin Level Checked
Your fasting insulin level reflects how healthy your blood glucose levels are over time. Your fasting insulin level can be determined by a simple, inexpensive blood test. A normal fasting blood insulin level is below 5, but ideally you'll want it below 3. If your insulin level is higher than 3 to 5, the most effective way to optimize it is to reduce or eliminate all forms of dietary sugar, particularly fructose.
There is also indication that a wide range of chemicals and foods and/or food additives can contribute to insulin resistance, such as MSG, trans fats, gluten, cow’s milk and artificial sweeteners.4
You can also use a simple glucose test to check your fasting glucose level. Just realize that it's possible to have low fasting glucose but still have significantly elevated insulin levels. Generally speaking, a fasting glucose under 100 mg/dl suggests you're not insulin resistant, while a level between 100 and 125 suggests you're either mildly insulin resistant or have impaired glucose tolerance (sometimes referred to as pre-diabetes).
Limiting Excess Sugar, is Crucial to Protecting Your Brain Health
There is no question in my mind that regularly consuming excessive sugar will dramatically increase your risk of dementia and Alzheimer's disease, as consuming too much fructose will inevitably wreak havoc on your body's ability to regulate proper insulin levels.
Although refined fructose is relatively "low glycemic" on the front end, it reduces the affinity for insulin for its receptor leading to chronic insulin resistance and elevated blood sugar on the back end. So, while you may not notice a steep increase in blood sugar immediately following fructose consumption, it is likely changing your entire endocrine system's ability to function properly behind the scenes.
Additionally, refined fructose has other modes of neurotoxicity, including causing damage to the circulatory system upon which the health of your nervous system depends, as well as profoundly changing your brain's craving mechanism, often resulting in excessive hunger and subsequent consumption of additional empty carbohydrate-based calories.
In one study from UCLA, researchers found that rats fed a fructose-rich and omega-3 fat deficient diet (similar to what is consumed by many Americans) developed both insulin resistance and impaired brain function in just six weeks.5 Furthermore, the amount of experimental and clinical research that has piled up over the past 10 years linking fructose to over 70 disease conditions is nothing short of astounding.6
Since the average American diet is heavy in fructose, sugars and grains that will wreak havoc on your blood sugar levels and insulin sensitivity, this is a pervasive and serious issue. I view significantly reducing fructose consumption as one of the most important steps you can take to protect your brain function as you age.
About 85% of Americans are insulin and leptin resistant and are likely best served by limiting fructose intake, including that from fruit, to 15 and no more than 25 grams per day. If you are not insulin and leptin resistant and are well adapted to burning fat as your primary fuel then you could likely consume larger amounts of fruit, especially if you ate them immediately before or after a workout so the sugar would be burned as fuel.
5 Memory-Boosting Tips to Try Now
In the long run, making sure you’re eating a healthful diet is the key to stellar brain health. In terms of fructose, you’ll want to limit your intake to 25 grams per day (or less), and 15 grams or less if you are overweight or have diabetes, pre-diabetes, high cholesterol or high blood pressure. Embracing the strategies that follow may also give a hearty boost to your brainpower, help keep you mentally healthy and ultimately even make you smarter.
1. Exercise
Exercise encourages your brain to work at optimum capacity by stimulating nerve cells to multiply, strengthening their interconnections and protecting them from damage. During exercise nerve cells release proteins known as neurotrophic factors. One in particular, called brain-derived neurotrophic factor (BDNF), triggers numerous other chemicals that promote neural health, and directly benefits cognitive functions, including learning. Also, exercise happens to be one of the only ways you can enhance your utilization of fructose, as the depletion of your glycogen stores opens up a role for fructose for replenishment if used post-workout.
To get the most out of your workouts, I recommend a comprehensive program that includes Peak Fitness high-intensity exercise, strength training, stretching and core work.
2. Proper Sleep
The process of growth, known as plasticity, is believed to underlie the brain's capacity to control behavior, including learning and memory. Plasticity occurs when neurons are stimulated by events, or information, from the environment. However, sleep and sleep loss modify the expression of several genes and gene products that may be important for synaptic plasticity. Furthermore, certain forms of long-term potentiation, a neural process associated with the laying down of learning and memory, can be elicited in sleep, suggesting synaptic connections are strengthened while you slumber.
If you want a quick brain boost, a mid-day nap has been found to dramatically boost and restore brainpower among adults.7 You can also find 33 tips to help you get the shut-eye you need here.
3. Optimize Your Vitamin D Levels
Activated vitamin D receptors increase nerve growth in your brain, and researchers have also located metabolic pathways for vitamin D in the hippocampus and cerebellum of the brain, areas that are involved in planning, processing of information, and the formation of new memories. In older adults, research has shown that low vitamin D levels are associated with poorer brain function, and increasing levels may help keep older adults mentally fit.8
Appropriate sun exposure is all it takes to keep your levels where they need to be for healthy brain function. If this is not an option, a safe tanning bed is the next best alternative, followed by a vitamin D3 supplement. What's important is your serum level, so you need to get your vitamin D levels tested to make sure you're staying within the optimal and therapeutic ranges as indicated below.
![Vitamin D Level 25 Hydroxy D]()
4. Vitamin B12
Mental fogginess and problems with memory are two of the top warning signs that you have vitamin B12 deficiency. Vitamin B12, or rather a lack thereof, has been called the "canary in the cobalamine" for your future brain health, and recent research has bolstered the importance of this vitamin in keeping your mind sharp as you age.
5. Animal-Based Omega-3 Fats
Docosahexaenoic acid, or DHA, an omega-3 fat, is an essential structural component of both your brain and retina. Minus the water content, approximately 60 percent of your brain is composed of fats—25 percent of which is DHA (assuming you have adequate levels in your diet). DHA is found in high levels in your neurons -- the cells of your central nervous system, where it provides structural support. When your omega-3 intake is inadequate, your nerve cells become stiff and more prone to inflammation as the missing omega-3 fats are substituted with cholesterol and inflammation-feeding omega-6 instead. Once your nerve cells become rigid and inflamed, proper neurotransmission from cell to cell and within cells become compromised.
To compensate for our inherently low omega-3 diet, a high quality animal-based omega-3 supplement is something that I recommend for virtually everyone, especially if you're pregnant.