Can Excessive Carbohydrate Intake Lead to Dementia?
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A current book that is on the New York Times best seller list, Grain Brain: The Surprising Truth About Wheat, Carbs, and Sugar-Your Brain's Silent Killers, written by Neurologist Dr. David Perlmutter, asserts that a diet high in carbohydrates can actually be instrumental in the development of dementia. Perlmutter, who is a professor of Medicine at the University of Miami as well as a Fellow with the American College of Nutrition, has raised some important and interesting arguments in favor of this position. Yet, his arguments are far from airtight.
Perlmutter has pointed to the use of the A1C test that measures glycolated hemoglobin over a period of three to four months previous to the blood test. It provides an average blood sugar measurement. He does raise an interesting and important point. Often the test is used to measure the average metric of blood sugar over the past few months for many diabetics. However, it is really looking at more than that; it is looking at the glycation going on in the body, which ultimately leads to oxidative stress, free radical formation and inflammation. These are all harmful to the body and in particular, to the brain. He also points to recent studies that have shown an association between elevated levels of blood glucose and an increased probability for dementia. Furthermore, he states that even mild blood glucose increases, which can be in the high normal range, can still be detrimental and lead to glycation, inflammation and an increased likelihood for dementia. He states that too many physicians look at the blood glucose level and as long as it is within the normal laboratory parameters they feel comfortable with the results. However, he states that physicians should not be dismissive about these high normal results and should advocate lower blood glucose levels under 100. He states that regardless of the normal parameters, as they approach the high levels of the normal range, a person increases their probability for acquiring dementia. However, I am not sure how Dr. Perlmutter has determined this, or how much of a probabistic increase results if it does, and what is the mathematical means that he has used to determine this result?
Dr. Perlmutter does quote a number of studies that have found associations between higher carbohydrate dietary consumption and a higher risk for acquiring dementia. However, he further admits the shortcomings of many of these studies, which were observational. Therefore, although relationships were found between higher carbohydrate diets and the probability for acquiring dementia, this should not be interpreted as carbohydrates necessarily being causative. Without true experimental-based studies that are able to control for many of the confounding factors, too many possible variables could be influencing the relationships that have been witnessed in the studies cited by Perlmutter. Furthermore, the correlational studies, since they are not being held constant, all probably had quite different levels of what they viewed as higher carbohydrate levels. Therefore, how high is what is referred to as being too high as it relates to carbohydrate consumption? Where is the level of demarcation that quantifies a healthy level from a potentially harmful level? Finally, is there anything that he can quote and identify as an identifiable quantification that provides an empirical basis of support other than guesswork and an intellectual eyeballing of what he thinks in his clinical judgment are valid quantifiable parameters? The answers to these are far from clear and need greater empirical support.
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