If you have children you may recall the tale of Goldilocks and the three bears.  They were Momma Bear, Poppa Bear and Baby Bear.  The take home lesson from the story, at least regarding porridge, was that the best temperature was not too hot, not too cold, but just right.  Neurons have similar needs when it comes to glucose and insulin levels.  I refer to this "just right" concept as the "Goldilocks Principle."  The major fuel the brain burns is sugar, or more precisely glucose.  The body can make glucose and we can consume it, or foods containing it, in our diet.  White bread is an example of a food source of glucose.  The starch in the white bread is a large molecule composed of long strands of single glucose molecules linked together side to side.  These links, or chemical bonds, holding the glucose together must be broken apart during the digestive process.  When this occurs, the glucose is able to be absorbed.  Not only is it absorbed, it is rapidly absorbed.  More rapidly than the body can use it.  This allows it to build up in the blood stream.  As a matter of fact, if you are aware of the glycemic index of food (a quantitative scale that categorizes the impact various foods have on the blood sugar level), white bread sets the upper standard at 100.  To put this in perspective, white table sugar comes in at about 60.

When the blood sugar skyrockets upward, it sends a signal to the pancreas, an organ in the back of the abdomen behind the stomach, to release insulin into the circulation.  One of the functions of insulin is to allow the body to clear glucose from the bloodstream thus preventing the buildup of high blood sugar levels.  Other foods that contribute to this blood sugar surge are refined carbohydrates such as cakes, cookies, desserts, and soda.  These are staples in the average diet of most Americans.  When consumed throughout the day, this type of diet produces a roller coaster effect on blood glucose and insulin levels.  High, then low, then high, then low and so on cyclically over and over throughout the day.  From the brain's perspective it is exposed to blood sugar levels of 150, then 60, then 140, then 65, and so on.  The reason for the very low, sometimes too low, sugar levels, is that after insulin clears most of the glucose from the blood it is  itself cleared more slowly and thus 'hangs around' for awhile.  This allows it to drive down blood sugar levels below normal.  You might have experienced this a couple of hours after a meal when you felt jittery, dizzy, or mentally woozy.  Welcome to the world of hypoglycemia (blood sugar that is too low).  Since the most potent stimulus for appetite is a low, or falling, blood sugar level you feel quite hungry.  If refined carbs are eaten, they initiate the cycle again.  This is the typical dietary roller coaster based upon an inability to feel satisfied and not hungry for prolonged intervals.  You have just eaten and are hungry again.  If you have been here before, you now know why.

These recurrent surges of glucose are bad for the brain.  Since the brain isn't able to store glucose in any meaningful amount, it depends on a stable, continuous supply.  When we become hypoglycemic, neurons are not able to maintain the high energy levels they depend on for optimal functioning.  When glucose and insulin  levels are elevated two things happen.  To protect themselves from these extremes, neurons tend to become 'resistant' to the action of insulin, and insulin levels in the brain fall.  This is exactly what is observed in the brains of patients suffering from Alzheimer's disease, and to a lesser extent, in persons with failing memories.  To prevent this, our goal should be to maintain a persistent and stable blood glucose and insulin level.  This is determined by dietary means.  It requires the avoidance of refined carbohydrates including fructose and HFCS (high fructose corn syrup, or all corn syrup, for that matter) and trans fats (partially hydrogenated oils, usually corn oil, safflower oil, or cottonseed oil).  Good foods for the brain include those with lean protein and essential omega 3 fatty acids such as eggs, cold water fish, walnuts, and flax and pumpkin seeds.  Non-starchy fruits and veggies such as berries of all types, avocados, olives, spinach, colorful bell peppers and so forth are also at the top of the list.  In addition, I love spices of all sorts.  They contain wonderful nutrients and literally no calories and include turmeric, sage, ginger, rosemary, and cinnamon to name a few.  It is necessary to avoid excessive calories.  A lean body is usually the home of a happy brain.  If you build your diet based upon these guidelines, you will be doing your brain (and body) a big favor!