Editor's Note :
In his new book Grain Brain: The Surprising Truth About Wheat, Carbs, and Sugar -- Your Brain's Silent Killers, Dr. David Perlmutter, Associate Professor at the University of Miami School of Medicine, advocates that lifestyle modifications, starting with a high-fat, nearly carbohydrate-free diet, can prevent or greatly lower dementia risk and progression -- and he's armed with plenty of data to back up the claim. But detractors say the evidence isn't quite there. With Grain Brain about to hit its 15th straight week on the New York Times best-seller list (including a stint at the top spot) Medscape spoke with Dr. Perlmutter about his thoughts on the impact of carbohydrates and gluten on the brain.
Medscape: For those unfamiliar with your ideas, can you summarize the thesis behind your new book and how you arrived at it?
Dr. Perlmutter: Certainly. I'm a board-certified neurologist and a fellow of the American College of Nutrition. I've been very frustrated with neurology over the past 20 years, because we're trained in residency and practice to basically treat symptoms of neurologic disorders. I found that not to be satisfying and thought it was important to delve into causality as opposed to just focus on treating the smoke and ignoring the fire.
That said, with time we began seeing wonderful research citations that were drawing a link between risk for dementia, for example, and blood sugar levels appearing in our most well-respected journals. For example, a study published in Neurology in 2005 pointed a finger squarely at the most powerful metric being glycated hemoglobin. Even back then, it was becoming clearer that there was something going on with blood sugar correlating with rate of brain atrophy, specifically hippocampal atrophy, and cognitive decline. When you now retrospectively evaluate that study, you begin to appreciate that glycated hemoglobin is more than just a metric of average blood sugar, which is typically how it's looked upon even today.
Glycated hemoglobin is a glycated protein. This is a marker not just of average blood sugar, but more important, it's a marker of the degree of glycation that's going on in human physiology -- a process that increases inflammation and dramatically increases the production of free radicals and oxidative stress. So the idea that even subtle elevations of sugar, which is a dietary lifestyle choice, are related to risk for brain degeneration really began to crystallize.
This notion has gained traction and, I think, is profoundly supported by a couple of more recent studies. A study published in August 2013 in the New England Journal of Medicine (NEJM) was very supportive, indicating that even subtle elevations of fasting blood sugar translates to dramatically increased risk for dementia. This was a prospective analysis that measured fasting blood sugar and followed 839 men and 1228 women for a mean of 6.8 years. I'll quote the conclusion: "Our results suggest that higher glucose levels may be a risk factor for dementia, even among persons without diabetes."
Why? These are levels of 105 and 110 mg/dL -- levels that most doctors are going to be satisfied with. However, according to the study, these numbers translated into a significantly increased risk for dementia in individuals who were not demented.
Medscape: That is striking. However, I think it's important to point out that many of the studies you cite report associations between glucose and risk for dementia and don't necessarily prove causality, correct?
Dr. Perlmutter: You are 100% correct. I'll stand and take my lumps from those individuals who want to make the argument that there's no smoking gun here. But when a prestigious journal like NEJM calls our attention to this relationship effect in glucose and cognitive decline, we've got to take notice, especially at a time when we have no other choice. It's the best thing that we have going.
We know that a lower-carbohydrate diet is the right choice for the heart and the immune system. There's no downside to it. I offer it up as being supported by the current peer-reviewed literature. If that's as good as it gets, that's the best we have right now.
You can wage criticism that the NEJM study was not interventional. It wasn't a double-blind study testing some sort of pharmaceutical intervention. It was a prospective study that basically asked who's going to get dementia on the basis of fasting blood sugar levels.
Some people criticize prospective or even retrospective studies because they're not interventional. I tend to think that they can provide very, very valuable information. There's never been an interventional trial that's demonstrated that seatbelts are effective in reducing injuries in a car accident.
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Cite this: Dementia: Is Gluten the Culprit? - Medscape - Jan 21, 2014.