This is your brain on sugar

Philip J. Goscienski, M.D.

May 2007

Back in the Stone Age honey was the only source of sugar that resembled anything like what we drop into our shopping carts today. Honey wasn't an everyday food; seasonality and stings made it an occasional treat. In contrast, it's really difficult to avoid sugar now. Almost all prepared foods, from hot dogs to the mustard that we slap onto them, contain sugar. Take a look at the boxes and jars in your pantry to see how many of them don't contain some form of sugar.

A whopping 20 percent of the average American's calories come from sugar but eating foods made from refined flour adds to the problem. Digestion turns the starches in bread, cereal, cookies, pizza, potatoes, tortillas and rice into glucose, known as blood sugar.

Back when most of our calories came from whole grains and vegetables it was easy for our bodies to keep blood sugar levels within a narrow range of normal. Thanks to 20th century food technology that gave us refined flour, refined sugar and high-fructose corn syrup our blood glucose rises to excessive levels several times a day, more than our bodies can keep up with. The sugar that we don't burn off immediately is stored as fat. Those high blood glucose levels cause insulin level to rise several times a day as well and eventually our cells become insulin-resistant. That leads directly to type 2 diabetes, the fastest-growing chronic disease in the Western world.

The human brain needs sugar to work properly but when levels are higher than evolution programmed us for, sugar degrades brain function. Older adults with diabetes don't do as well on tests of memory and attention when they eat a meal that raises blood sugar as they do on a meal that produces a smaller rise. Even in persons who do not yet have outright diabetes, the higher the blood sugar, the worse the decline in memory.

Diabetes does its real damage by narrowing and distorting tiny blood vessels. By the time a person is diagnosed with diabetes there is already damage to blood vessels throughout the body. The brain has a very generous blood supply. It shouldn't be any surprise that mental performance isn't as good in persons with diabetes as it is in normal persons. Diabetics with good control of blood sugar do better in tests of mental performance than those who can't seem to manage their diet or medication.

It doesn't matter whether excessive calories come from too much sugar or too much refined grains; they all end up as fat. Piling on the pounds leads to high blood pressure. Children who have higher-than-normal blood pressure, even pre-teens, do less well on tests of brain function and the higher the blood pressure, the worse they perform.

The bottom line: if you avoid sugary and starchy foods your brain will work better and last longer. Start by switching to whole grains and making sugary desserts an occasional treat.

Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at