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Welcome back to the Neuroscience Meets Social and Emotional Learning Podcast, for Brain Fact Friday and episode #117.  Since we just released the ground-breaking interview with Dr. Ratey on the impact of exercise and nutrition on the brain, I wanted to focus today’s episode on something that he said, that caught my attention.

Since last week’s Brain Fact Friday was about “Building a Faster, Stronger, Resilient Brain, by Understanding Brain-Derived Neurotrophic Factor (BDNF)” or the compound that Dr. Ratey says is crucial for preventing cognitive decline and Alzheimer’s Disease, I wanted to focus this episode on something Dr. Ratey said that really made me think.


High Glucose Levels are Toxic to the Brain and Limits the Production of BDNF

He said, did you know that “High glucose levels are toxic to the brain, and limits the production of this glorious compound BDNF that has such a profound effect on cognition and well-being?”

I remember a powerful quote from a BONUS episode I did for Podbean’s Wellness week[i]  that goes right along with what Dr. Ratey said, coming from Dr. David Perlmutter, who wrote the foreword to Dr. Ratey’s book Go Wild![ii]

DID YOU KNOW THAT: Sugar in the brain looks like Alzheimer’s in the Brain?

I wrote in this bonus episode, after watching Dr. Perlmutter’s Alzheimer’s The Science of Prevention Series, Did you know that sugar in the brain “looks like Alzheimer’s” in the brain, and that “60% of cognitive decline is related to how you handle blood sugar?”[iii]

There was a study that followed “over 5,000 people over 10 years and found that people with high blood sugar had a faster rate of cognitive decline than those with normal blood sugar—whether or not their blood-sugar level technically made them diabetic. In other words, the higher the blood sugar, the faster the cognitive decline.”[iv]

So when Dr. Ratey said that “high glucose levels are toxic to the brain” I thought back to this study, and wellness episode, and thought we could take a closer look at how our glucose levels increase, with tips for healthy ways to keep our blood levels stable.

I’m sure we all know that sugar is bad news for our brain, our body, and that sugar (a class of molecules called carbohydrates) will give us a rush of energy at first but will make us hungry a few hours later). Now to think that it limits the production of this key protein we all know is important for anti-aging, and Alzheimer’s prevention.  Imagine that you have half the equation right. You are exercising, watching what you eat, and allowing some treats in moderation. This would be the perfect way to live your life, according to Dr. Ratey, but I started to wonder, what are some ways that we could unknowingly be raising our glucose levels and preventing the production of this powerful BDNF protein? Other than eating a bunch of sugar, are there other things I could be doing that could possibly be raising my glucose levels without me even knowing it? Until I heard Dr. Ratey talking about how damaging sugar was to our brain, I hadn’t spent much time thinking about this lately.

We don’t have to be diabetic to watch or be aware of our blood sugar or glucose levels. I mention in one of my earlier episodes[v] that it was a visit to a foot doctor around 2005 for foot numbness after exercise, that got me to eliminate sugar completely from my diet back then.  I was looking for solutions to why I couldn’t feel the top of my foot during exercise, and I didn’t show any signs of diabetes, but this doctor was writing a book, that is now released called Sugar Crush: How to Reduce Inflammation, Reverse Nerve Damage and Reclaim Good Health[vi] and he was convinced that sugar intake was at the root of most health problems. He suggested that I take fish oil, and learn to avoid higher glycemic foods, and the results that occurred were so impactful, that I wished I had done this sooner. The benefits of cutting out sugar from my diet back then snowballed my health for the better down the road. But here I am 16 years later, and not suggesting an elimination diet (unless you want to fix something like I did) but knowledge is power. I think being more aware of the impact that sugar or glucose has on our brain will help us to all make better, healthier decisions for ourselves and families.

But First, What Exactly Does Sugar Do to the Brain?[vii]

When the sugary treat that you are eating (a bit of chocolate, cookie or cake) hits your tongue, your cerebral cortex registers the taste as sweet versus bitter or salty. Next, the brain’s reward system is activated and this part of the brain that loves the sugar you just ate, light up.  The neurotransmitter dopamine, part of our reward system is released, and your body begins to produce more chemicals like insulin to offset the sugar. You can either have just a little bit, and not create much damage to your brain (which is why I think it’s ok to eat a few bites of whatever sugary treat you like—chocolate is something I personally love to eat even though my old foot doctor would probably not be happy to hear this) but for some reason, if you can’t just take a few bites, and your brain is telling you to “eat more” then you will find it difficult to stop eating the treat and it will damage your brain and body, like Dr. Ratey explained.

What Else Spike Our Blood Sugar? I had no idea that there were so many other ways that we can increase glucose in our brain. Did you know about these 10 surprising things that can spike your blood sugar?[viii] According to an article on, sunburn, artificial sweeteners, coffee, not enough sleep, dehydration and gum disease all spike your blood sugar levels?

What Lowers Our Blood Sugar? We all know that movement and exercise lowers blood sugar, and I am sure we could all guess that managing our carb intake also helps to reduce blood sugar levels and prevent blood sugar spikes[ix], since carbohydrates are mostly glucose.  But did you know that “increasing your fiber intake improves the body’s ability to regulate blood sugar”[x] or that “drinking water and staying hydrated lowers blood sugar levels?”[xi]

I’ve included all the links to the research I did on this topic in the show notes if you would like to dig a bit deeper into the damaging effects of sugar on the brain, but I think we have made a clear case for thinking hard about the next sugary treat we eat, or what we buy for our families at the grocery store.

I hope this brain fact inspired by Dr. Ratey, has made you think. If you haven’t listened to his episode #116 yet, go back and listen to it, and stay tuned for next week, where I will dive deeper into his books. We only scratched the surface in our interview together, and there’s so much more to uncover.

See you next week!


[i] Neuroscience Meets Social and Emotional Learning BOUS EPISODE “ A Deep Dive into the Top 5 Health Staples, and a Review of Seasons 1-4”

[ii] Go Wild: Eat fat, Run Free, Be Social, and Follow Evolution’s Other Rules for Total Health and Well-Being by John J. Ratey, MD and Richard Manning (June 3, 2014)

[iii] Dr. David Perlmutter’s “Alzheimer’s: The Science of Prevention” EPISODE 5

[iv] The Startling Link Between Sugar and Alzheimer’s by Olga Khazan Jan. 26, 2018

[v] Neuroscience Meets Social and Emotional Learning BOUS EPISODE “ A Deep Dive into the Top 5 Health Staples, and a Review of Seasons 1-4”

[vi] Sugar Crush: How to Reduce Inflammation, Reverse Nerve Damage and Reclaim Good Health by Dr. Richard Jacoby (April 2014)

[vii] How Sugar Affects the Brain by Nicole Avena, Published on YouTube January 7, 2014

[viii] 10 Surprising Things That Can Spike Your Blood Sugar


[x] 15 Ways to Lower Blood Sugar Levels Naturally by Arlene Semeco December 21, 2020