The Ravages of High Blood Sugar and How to Save Your Brain from it

Sugar Excess: An Alarming Epidemic

Undeniably, you need sufficient blood sugar to power your brain. And quick jumps in blood sugar can be beneficial when you are taxing your brain to learn something new or when an aging or demented brain needs extra stimulation. But the truth is millions of American brains are threatened by the opposite hazard: chronically high circulating levels of blood sugar and its companion, the hormone insulin. Such high levels of glucose and insulin day after day can result in degradation of memory and mental functioning, partly because of so-called “insulin resistance” or “predia­betes.” If you are genetically susceptible, especially if you are overweight, such insulin resistance may also lead to Type 2 diabetes with increasing likelihood of blood sugar control, heart disease, and neurological complications, even Alzheimer’s disease.

How You Make Blood Sugar

Here’s what happens: When you eat carbohydrate—plain sugar or starch, such as pasta, potato, bread, beans—it is digested and converted mainly into the single sugar mole­cule, glucose, that is absorbed into the bloodstream. This infusion of glucose signals the pancreas to make more insulin, the hormone needed to usher glucose into the cells where it can be burned as fuel. Insulin’s job is to efficiently process the glucose, getting blood sugar levels back to nor­mal.

It usually goes smoothly if blood sugar rises are gradual. But if blood sugar surges too high, too fast, from eating lots of quickly digested carbohydrates, the pancreas must churn out more insulin in attempts to control glucose. If that hap­pens over and over, year after year, the pancreas can become exhausted, eventually putting out insulin that is too weak and insufficient to control blood sugar. The cells then become insensitive or “resistant” to the insulin. The pan­creas frantically spews out more insulin to try to clear blood sugar. The potential catastrophic result is a condition called “insulin resistance”—the inability to fully utilize insulin—that can lead to Type 2 diabetes or independently to vascu­lar problems, such as high blood pressure and thickened carotid arteries, affecting the brain.

Insulin resistance is a hallmark of diabetes. Addition­ally, millions of Americans—an estimated 25 percent of adults—not known to have diabetes are insulin resistant. The condition is a rapidly growing epidemic, tied to high-fat, high-processed-foods diets, with severe consequences for the brain.

BOTTOM LINE: High levels of blood sugar or glucose create high blood levels of insulin. These twin devils can be hazardous to your brain, blood vessels, and the rest of your body.

HOW HIGH BLOOD SUGAR AND INSULIN HARM YOUR BRAIN

High insulin levels are a prelude to high blood pressure, a prime risk factor for intellectual decline in later life.High blood sugar and high insulin tend to make arteries more stiff and less elastic, restricting blood flow to the brain.High blood sugar and high insulin stimulate a thickening of the walls of the carotid arteries. Such carotid thickening is a major factor linked to a loss of cognitive function with age.

Insulin resistance is tied to a sensitivity to sodium that tends to raise brain-damaging blood pressure.

The Mental Ravages of High Blood Sugar

There’s extensive and growing evidence that your brain rebels against persistent high blood sugar. Undeniably, abnormalities in blood sugar and insulin cause disturbances in memory and brain function. It happens in youngsters and adults, in those with active diabetes and in countless mil­lions who don’t even know they have hazardously high blood sugar. The mental toll is most apparent in older people when years of cumulative damage begin to show up as severe loss of memory and intellectual functioning. The clear message: Controlling high blood sugar, and insulin, should be a high brain-saving priority at all ages.

Here’s some of the compelling evidence:

Abnormally high blood sugar in diabetic children can cause a significant drop in IQ scores.

Older people with “persistent impaired glucose toler­ance,” probably due to high insulin levels, score lower on tests of overall mental function and long-term memory. Older diabetics are three times more apt to show signs of cognitive decline in standard mental testing.

Striking evidence of the dangers of chronic high blood sugar to intellectual functioning comes from the so-called Zutphen Elderly Study by Dutch investigators. In the study, men between ages sixty-nine and eighty-nine were given oral glucose tolerance tests and a standard measure of cog­nitive function called the Mini-Mental State Examination. The results: The number of errors on the mental function test climbed along with levels of fasting blood sugar.

Specifically, known diabetics (with the highest blood sugar levels) made 23 percent more errors on the test, newly diagnosed diabetics, 16 percent more errors, and those with impaired glucose tolerance (prediabetes) made 18 percent more errors than those with normal blood sugar tolerance. Further, nondiabetics with the highest blood insulin levels made 25 percent more mistakes on the mental test than those with the lowest insulin blood levels. Nondiabetic sub­jects with impaired glucose tolerance and abnormally high insulin had impaired cognitive function as measured by the routine mental test.

One theory: High insulin might be detrimental to “synaptic activity” in the brain, interfering with message transmission between brain cells, concluded researchers.

High blood sugar predicts strokes. Diabetics have three times the risk of stroke as nondiabetics. Even nondiabet­ics with nonfasting high blood sugar (over 225 mg/dL) have double the odds of “blood clot” stroke than men with low to normal blood sugar, (under 151 mg/dL), according to a recent twenty-two-year study of about 7500 Japanese-American men. High blood sugar did not raise the chances of a bleeding or hemorraghic stroke. Further, high blood sugar was tied to more strokes regardless of whether the men had high blood pressure.

Why is unclear. But autopsies show that diabetics have more severe atherosclerosis in the small blood vessels of the brain as well as in the carotid (neck) arteries that feed the brain.

High blood sugar and insulin encourage age-related dementia (general intellectual decline) and Alzheimer’s dis­ease. A recent study at the Mayo Clinic found that Type 2 (adult onset) diabetics were 66 percent more apt to develop all types of dementia, and male diabetics had more than twice the risk of developing Alzheimer’s disease. Diabetes tripled the odds of dementia and Alzheimer’s in a recent large-scale study at the University of California at Davis.

Main message: A jump in blood sugar levels is okay sometimes (it’s normal after eating) and can benefit learn­ing and memory on a short-term basis. Chronic high lev­els of blood sugar and insulin over long periods of time are dangerous and can be detrimental to optimal brain func­tion.

DIABETES OF THE BRAIN?

It’s a new and controversial idea: that insulin affects memory, learning, and general brain function far more deeply than previously thought. Some researchers even contend that neurons, just like other cells, need insulin to process glucose—an idea that flies in the face of long-time conventional belief.

Such scientists suggest that insufficient or “low voltage” insulin could starve neurons of glucose, leading to a partial power outage or “brownout” of the brain, resulting in weak­ened message transmission, a slump in learning, and memory failure of the type seen in age-related impair­ment and Alzheimer’s disease. In a word, memory dis­turbances due to ineffectual insulin inside brain cells might be a kind of “diabetes” or prediabetes of the brain.

That’s what neuroscientist Siegfried Hoyer at the University of Heidelberg in Germany theorizes. He finds that rats with brains made resistant or insensi­tive to insulin quickly develop memory loss, which pro­gresses to an Alzheimer’s-like state. He, as well as neuroscientist Suzanne Craft at the University of Washington, have found insulin disturbances in the brains of Alzheimer’s patients. “We believe that some cases of Alzheimer’s disease are like diabetes mellitus,” says Dr. Hoyer.

How to Save Your Brain from High Blood Sugar

What can you do to avoid this brain menace? What makes blood sugar and insulin soar and stay at abnormally dan­gerous levels? Obviously, genetic makeup influences blood sugar; some people are blessed at birth with good blood sugar control. Others are more genetically vulnerable to developing insulin resistance and diabetes. But genes are far from destiny. Lifestyle, including the foods you eat, can dramatically influence blood sugar and insulin levels and override a predisposition to such conditions.

Indeed, evi­dence shows that the rise in insulin resistance and dia­betes is closely tied to diet. Restricting saturated animal fat can go a long way to avoiding and correcting insulin resistance and diabetes. Also critical are the carbohy­drates—sweets and starches—you eat, for carbohydrates, especially of the “wrong” type, can spike blood sugar and insulin, often leading to persistent high blood sugar, insulin resistance and diabetes, and possibly compromised men­tal function.

Brain Perils of Your Diet

Our modern diet is a minefield of hazards to blood sugar normalcy, and quite out of sync with the diet of our ancient ancestors. The prehuman evolutionary diet that formed our brains, mandating high requirements for glucose, was rich in carbohydrates just as high as ours—about 65 per­cent of calories. The difference is the type of carbohy­drates. The early carbs came from fruits, vegetables, and beans, as well as honey.

Ours come from refined sugar and finely processed flour made into blood-glucose-spiking cereals, bread, and other baked goods. Although grains and dairy foods are “new” in evolutionary terms, even they, ten thousand years ago, were quite different in their impact on blood sugar. They were mostly whole grains and yogurt; consequently they produced gradual blood sugar rises that were compatible with good brain function.

Today’s staples, such as bread, are made from fine-particle flours that fly through our digestive system, spiking our blood sugar.

“With the advent of high speed roller mills in the nine­teenth century, it was possible to produce white flour so fine that it resembled talcum powder in appearance and texture. . . . As a consequence . . . the blood sugar rise after a meal was higher and more prolonged, stimulat­ing the pancreas to produce more insulin. . . . Thus, one of the most important ways in which our diet differs from that of our ancestors is the speed of carbohydrate digestion and the resulting effect on blood sugar and insulin levels.” —Dr. Jennie Brand-Miller, University of Sydney in Australia, The Glucose Revolution

Unquestionably, carbohydrates, as well as animal fats, can play havoc with blood sugar and insulin, and thus with memory and other mental functions. But this does not mean you must avoid carbohydrates. Because of the newly discovered hazards of carbohydrates in promoting high cir­culating levels of blood sugar and insulin, as well as obe­sity, a flurry of popular advice warns against the intake of carbohydrates. This erroneously assumes carbohydrates of all types are hazardous.

The confusion comes from a mis­perception that carbohydrates are equally treacherous in their ability to endanger the brain by dy’sregulating blood sugar and insulin. That is far from true. Certain carbohy­drates nourish your brain without upsetting blood sugar and insulin. The trick is to know which carbohydrates are good for your blood sugar and brain, and which are not.