A recent study provides a clue into the exercise-brain fitness relation. A paper reported in the December 2008 issue of the journal Neurology shows that high levels of blood glucose (the kind that can happen in people with diabetes) may directly affect the hippocampus. Since the hippocampus is a part of the brain that is essential for memory, this study helps us understand one way in which physical fitness can affect brain function. What’s the link? We know that physical fitness improves the body’s ability to regulate blood sugar levels, so being physically fit may decrease the damage that high blood sugar levels can cause to the hippocampus.
The story is a little more complicated, though (isn’t it always)? Blood sugar is regulated by a hormone called insulin. People who have type II diabetes (the kind that people usually get later in life) have a condition called insulin resistance. This means that the body makes enough, and sometimes too much, insulin. The problem is that the insulin doesn’t have a strong enough effect. This means that the body keeps making higher levels of insulin. Exposing the body to high levels of insulin can cause problems.
In the case of the brain, insulin is very important for its function. Insulin has to cross into the brain from the blood by way of a special mechanism called a transporter protein. When insulin levels are high all the time, the body decreases the number of these transporter proteins, and the brain may not get enough insulin. Some studies have shown that insulin is important in memory function, so a decrease in the number of these transporter proteins may be yet another way that high blood sugar levels can affect memory. While all of these studies are preliminary, they add to what we know about high blood sugar, insulin resistance, and mental functioning.
There are two effective ways of keeping your blood sugar under control: diet and exercise. Following the Mediterranean diet can help, because it emphasizes the kinds of food that will help keep your blood sugar stable. Exercise has been shown to help your body be more sensitive to the effects of insulin. When your body is more sensitive to insulin’s effects, blood sugar levels will be lower and more stable. We know that following the Mediterranean diet and regular exercise can help your memory – their link to blood sugar and blood sugar’s effects on the brain may be why.