As the body ages, glucose tends to linger in the blood after a meal. In response, the pancreas pumps out more insulin, the hormone that helps usher glucose into muscle cells, but the cells don't respond to the insulin as vigorously as they used to.
This produces two unhealthy conditions: elevated levels of glucose and elevated levels of insulin. Both are considered to contribute to clogged arteries, inflammation and other problems related to aging.
Now research has provided disturbing evidence showing that high levels of glucose may affect the memory as well. Fortunately, there's a simple and inexpensive way to counteract this: Eat less and exercise more.
Dr. Scott Small of Columbia University Medical Center has found that elevated glucose in the blood affects the dentate gyrus, a portion of the brain vital to the creation of short-term memories. "As we age our muscle cells become less sensitive to insulin, so we have glucose spiking in our blood, and the dentate gyrus is particularly sensitive to fluctuations in glucose," Small said. "Too low is worse than too much."
People with diabetes are more prone to memory problems even if they don't have Alzheimer's disease, and their difficulty absorbing glucose into their cells could explain why.
As a result of his research, Small has joined a gym.
"All of us, beginning at about the age of 30, have greater and greater difficulty handling glucose," he said. "I'm 47. A study we did a couple of years ago found that physical exercise improves the function of the dentate gyrus by improving glucose utilization."
Eating less may also help mitigate memory loss, according to German researchers. They divided 50 healthy elderly subjects into three groups. Twenty of them reduced their calorie intake by 30 percent, 20 ate more fish and olive oil, which contain fatty acids believed to be beneficial to the brain, and 10 made no change in their diet. After three months the group that reduced their caloric intake scored 20 percent better in a test that involved remembering lists of words.
At Northwestern University in Evanston, Ill., researchers found that when they treated brain cells in the laboratory with insulin and a drug used by diabetics to increase their sensitivity, the cells became less susceptible to the protein fragments thought to trigger Alzheimer's. William Klein, the leader of the research, has found that these protein fragments cause brain cells to lose their insulin receptors, a process that makes him think of Alzheimer's disease as "type 3 diabetes."
"Therapeutics designed to increase insulin sensitivity in the brain could provide new avenues for treating Alzheimer's disease," he said in a statement released with his recent paper. "Sensitivity to insulin can decline with aging, and our results demonstrate that bolstering insulin signaling can protect neurons from harm."
Freelance writer Tom Valeo writes about medical and health issues.