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Making memories

The brain needs fuel to store and retrieve memories.

This simple fact is at the heart of a new study that sheds light on the reason why many tend to experience a loss of memory as they grow older. But this aspect of aging shouldn’t be casually accepted as a situation that everyone has to cope with. Because, as the study reveals, there are simple steps that most of us can take to avoid the deterioration of memory.



Glucose delivery

Most body tissues receive their energy from multiple sources. The brain, however, depends on blood sugar for almost all of its fuel. Knowing this, researchers at New York University (in association with the Nathan Kline Institute for Psychiatric Research) designed a study to find out if there was a link between slightly elevated blood sugar levels (also known as glucose intolerance) and memory performance.

Thirty subjects were recruited. All were in their 60s or early 70s, and none were diabetic, although some had levels of blood sugar that were higher than normal. The NYU team began by measuring the size of each subject’s hippocampus (the unusual name for the brain region responsible for recent memory). Cognitive function was measured with a standardized test, while memory was determined with a series of tests that asked subjects to recall paragraphs of different lengths. Finally, glucose regulation was assessed after an overnight fast, using an intravenous glucose tolerance test.

When the researchers analyzed the data, the subjects with glucose intolerance scored lower on the tests for recent memory compared to subjects with normal blood sugar levels. Furthermore, each of those with impaired glucose tolerance also had a smaller hippocampus. These results suggest that the delivery of glucose to the brain may have an effect on the function of the hippocampus, as well as its structure and size.

The conclusion: Elevated blood sugar levels may be one of the primary causes of memory loss among the elderly.

Getting the cycle right

As we grow older, our cells gradually become resistant to insulin – the hormone that regulates blood sugar. This is one of the reasons why a higher than normal blood sugar level is a typical condition of aging. So if the brain needs blood sugar to operate, and if the levels are high, why would this create a memory problem? Because when the levels are elevated the flow of glucose from the blood to the tissues is impeded. Eventually (as the NYU study demonstrates), the reduced supply of glucose may cause the hippocampus to atrophy, which affects the memory and may contribute to more severe problems such as dementia and Alzheimer’s disease.

Fortunately, there is a way to help your cells stay sensitive to insulin and more efficient in processing blood sugar. Two words: Diet and exercise. Okay, that’s three words, but you get the idea.

The exercising part is fairly simple – exercising increases blood flow to the tissues, which helps improve insulin sensitivity. As for diet, I don’t have to tell you that the debate about what constitutes a proper diet is still raging. But in a well-known lecture about the metabolic effects of insulin, Ron Rosedale, M.D. (of the Colorado Center for Metabolic Medicine), presented the case for a diet that balances protein and carbohydrates, with this important note: carbohydrates with fiber (i.e.; broccoli and apples) help improve insulin sensitivity, while carbohydrates without sufficient fiber (i.e.; potatoes and highly processed bread) raise the blood sugar level.

Like all of us, I’m certainly not getting any younger. So I’m on my way out now for a brisk walk to my local grocery for apples, oranges and apricots.

To Your Good Health,

Jenny Thompson

Health Sciences Institute

“Reduced Glucose Tolerance is Associated With Poor Memory Performance and Hippocampal Atrophy Among Normal Elderly” Proceedings of the Nation Academy of Sciences, 2/5/03 (epub ahead of print)
“High Sugar Blood Levels Linked to Poor Memory” New York University Medical Center and School of Medicine,, 2/5/03
“Insulin and Its Metabolic Effects” Ron Rosedale, M.D. Lecture presented at Designs for Health Institute’s Blouder-Fest, August 1999,