Dr Jedha, Host
Hello wonderful people. You’ve no doubt heard of type 1 diabetes, and of course, prediabetes and type 2 diabetes, but have you ever heard of type 3 diabetes? Many people haven’t and it’s the topic of today’s chat.
When I first came across this way back in 2015, it was incredibly interesting then, especially with the shocking statistic that was quoted by researchers back then, that living with type 2 diabetes puts you at a 50-150% risk of getting type 3. A recent research review on this topic came into my radar so I thought I’d share all this with you.
In today’s episode, we’re going to unpack what type 3 diabetes actually means, why some researchers use this term, and why it’s to know about, for prevention. Let’s explore some of the science, and what actions we can take to lower risk as well.
First, let’s just recap an important point about prediabetes and type 2 diabetes, because it really helps explain where type 3 diabetes fits in.
Prediabetes and type 2 diabetes are conditions driven by insulin resistance. That means the body’s cells don’t respond properly to insulin, the hormone that allows glucose to move from the blood into the cells for energy. We’ve spoken in detail about this in episodes 26 and 70 and throughout many other podcasts. So here’s the thing, when insulin resistance develops, the pancreas has to pump out more and more insulin to try and keep blood sugar under control, which can worsen insulin resistance and become a repetitive cycle, especially if nothing is done about this. And this underlying issue of insulin resistance, this is the very interesting area that researchers have explored.
So let’s start with where this term even comes from — type 3 diabetes.
Researchers noticed that people with type 2 diabetes have a much higher risk of developing dementia, particularly Alzheimer’s disease. In fact, studies show the risk is around 50–60% higher compared to people without diabetes and prevalence of dementia in people over 75 living with diabetes is around 24%, so these prominent connections made scientists curious. And when scientists began looking closely at what was happening inside the brain, they found something very familiar: insulin resistance.
The brain is a hungry organ. It uses about 20% of the body’s energy, and glucose is its main fuel. But glucose can’t get into cells without insulin working properly. When insulin signaling in the brain breaks down, neurons, which are the brain’s nerve cells, don’t get the fuel they need. Over time, this leads to problems with memory, thinking, and eventually the structural changes we see in Alzheimer’s disease, like amyloid plaques and tau tangles.
So the idea of type 3 diabetes is that Alzheimer’s may, in part, be a form of diabetes in the brain, where insulin resistance and disrupted glucose metabolism drive the disease process. Not the only cause, but a major player.
Researchers propose that once insulin resistance takes hold in the brain, several damaging processes begin to unfold.
First, the brain’s natural clean-up crew struggles. Insulin normally helps regulate an enzyme that breaks down both insulin itself and amyloid-beta, the sticky protein that forms plaques. In insulin resistance, people often have insulin levels, the pancreas releases more and more insulin to try to get glucose out of the bloodstream and into the cells. But when insulin levels are chronically high, this clean-up enzyme in the brain gets overwhelmed, spending its time on insulin and leaving amyloid-beta to accumulate. Amyloid plaques block the signals between neurons and they also release beta-amyloid, a toxin that that injures neurons in the brain. As a consequence, regions of the brain slowly begin to decline. So, over years, these plaques interfere with brain signaling and damage surrounding tissue.
Second, there’s the problem of tau. Tau is a structural protein inside neurons, kind of like scaffolding. In type 3 diabetes, insulin resistance triggers enzymes that cause tau to become twisted and tangled. These tangles block the cell’s transport system and eventually lead to cell death.
Then comes inflammation. The brain’s immune cells, called microglia, get switched on and stay on. Instead of protecting the brain, they pump out inflammatory chemicals that worsen the damage. At the same time, oxidative stress, which is basically like rusting at a cellular level, it adds to the injury.
And underpinning all of this are mitochondria, the cell’s power plants. In insulin resistance, mitochondria become less efficient, producing less energy and more free radicals. That makes it even harder for neurons to survive.
So rather than one single cause, researchers propose type 3 diabetes is a web of interlinked problems — plaques, tangles, chronic inflammation, oxidative stress, and cellular energy failure. But at the very center of this web is insulin resistance. It’s that breakdown in insulin signaling that sparks the cascade, tipping the brain into an energy crisis and setting the stage for all the other damage we see in Alzheimer’s disease.
While all this may sound concerning, here’s the important thing: this doesn’t happen overnight. These changes start decades before symptoms show up, which means what you do in your 40s, 50s, and 60s can make a huge difference to your brain health later in life. And even more important, this emphasizes why it’s so important to be proactive and regulate your blood sugar and optimize your health – to reduce your risk of type 3 diabetes.
While scientists are still debating whether Alzheimer’s should officially be called “type 3 diabetes,” what’s clear is that insulin resistance is a major trigger for the cascade of brain changes we just talked about. Insulin resistance is something we can influence.
And let’s not forget that at the center of it all is dysregulated glucose. When blood sugar runs too high for too long, as it can in prediabetes and type 2 diabetes, it doesn’t just affect your pancreas or your circulation, it also affects your brain. Chronically high glucose fuels oxidative stress, forms damaging molecules called advanced glycation end products, and drives even more insulin resistance. That combination sets the stage for the brain’s energy crisis, plaque build-up, and inflammation.
This is why prevention is so powerful. Alzheimer’s and other dementias don’t appear out of nowhere. The changes in the brain begin decades before the first memory lapses show up. We already know from type 2 diabetes research that keeping glucose stable, improving insulin sensitivity, lowering inflammation, and maintaining healthy weight, all reduce the risk of complications. And those same actions also help to protect the brain.
So rather than waiting for a cure, prevention is our strongest tool. By being proactive in stabilizing blood sugar and supporting insulin function now, you’re not just protecting your body from diabetes complications, you’re also investing in your long-term memory, focus, and independence. And those things are very important to us all.
So if prevention really does start with stabilizing blood sugar and improving insulin sensitivity, what does that look like in everyday eating? Well, it comes down to many fundamentals that we often talk about here on the podcast. The nutrition strategies that make a big difference for diabetes, also have a big impact on brain health.
Cutting out or cutting down on added sugars and the refined carbs found in many processed foods. These are the biggest drivers of blood sugar spikes and insulin resistance. Every time your blood sugar shoots up, it stresses the brain as well as the body. Think of it like a rollercoaster ride – the energy ups and downs, these become damaging over time to cells throughout your body and to the brain. Keeping those spikes lower helps your brain get a steady supply of energy rather than a chaotic one.
Did you know that the brain is made up of about 60% fat, so it makes sense that it thrives on quality fats. Science shows us that the fats that help reduce inflammation, improve insulin sensitivity, and support cell membranes are those rich in monounsaturated fat and omega-3s, so we’re talking lots of olive oil, the benefits of which we covered in episode 14, the deliciously creamy avocado, along with nuts and seeds. And omega-3 rich fish like salmon, or seeds like chia and flax.
Prioritizing protein, which we frequently talk about and that’s because it’s so important to help keep blood sugar steady and preserve muscle mass, which are both vital factors for insulin sensitivity. Good protein at each meal, whether that’s eggs, fish, chicken, Greek yogurt, or plant-based options like tofu, gives your brain the amino acids it needs for neurotransmitters, the chemicals that keep you thinking clearly.
Eat lots of vegetables, lots of them, in all different colors for their antioxidants and polyphenols and lots of leafy greens. Berries and nuts are also excellent sorts of antioxidants and polyphenols with potential neuroprotective effects. Overall, there’s no one single nutrient that prevents or treats the condition, but what we do know is that its’ the quality of your overall nutrition plan that matters most and that’s why we discuss that a lot throughout the podcasts.
I want to touch on one area of research that’s been emerging for sometime — the gut-brain connection.
We often think about Alzheimer’s, or type 3 diabetes, as purely a brain issue. But a growing number of studies are showing that the health of our gut microbiome, that community of trillions of bacteria living in the digestive tract, may play a role in how our brain ages and be linked directly to our brain health.
That is absolutely crazy to imagine, right? How can these bacteria in our gut have any impact on our brain? Well, the gut and brain are in constant communication through what’s called the gut-brain axis. When the gut microbiome is healthy and diverse, it produces beneficial compounds like short-chain fatty acids that reduce inflammation and support brain health. But when the microbiome is out of balance, what researchers call dysbiosis, it can trigger systemic inflammation and even affect insulin resistance, both of which feed into the processes we see in type 3 diabetes and Alzheimer’s.
Several recent reviews have highlighted this link, and we’re seeing this connection between our gut and many aspects of our health appear, again and again. And this emphasizes again why the quality of your overall nutrition plan really, really matters. Eating lots of vegetables, green leafys, nuts and seeds, small amounts of legumes and beans, these all nurture a healthier gut microbiome, growing more of those beneficial type and reducing the bad guys causing havoc. And of course limiting the sugar and refined carbs and processed foods, not only does all of this support better blood sugar control, it improves the gut microbiome. And in turn, emerging evidence tells us this will also help protect against cognitive decline and dementia risk. Probiotic supplements are also being studied, but the strongest evidence right now points to real foods and a quality nutrition plan as being your best form of defence.
Which is great news of course, as that’s exactly what we chat about a lot on hte podcast and what we help our members do each and every day – discover a nutrient dense eating plan that feels natural and sustainable for them long-term. And I know many members find this podcast motivational, confirming their decision to eat well and thrive each day.
Before we finish up, it’s important to acknowledge that not everyone agrees with the term “type 3 diabetes.”
Alzheimer’s disease is complex. Genetics play a role. Vascular health, toxins, head injuries, and lifestyle factors all add to the picture. So while insulin resistance and dysregulated glucose are strong contributors, they’re not the only ones. Some researchers worry that calling Alzheimer’s “type 3 diabetes” oversimplifies a very complicated disease.
That said, the evidence linking blood sugar problems and brain health is too strong to ignore. Insulin resistance may not explain everything, but it appears to be a major trigger , one that we actually can do something about. And that’s where the prevention message becomes so powerful.
Looking to the future, this area of research is only growing. We’re seeing more focus on nutrition patterns, gut microbiome research, and lifestyle factors that support both metabolic health and brain health. There’s also ongoing investigation into medications and novel therapies, but for now, the most effective tools we have are the daily choices around food, activity, stress, and sleep.
So the debate is healthy, and science is still evolving. But one thing is clear: what’s good for your blood sugar is good for your brain. By lowering those daily blood sugar spikes, achieving and maintaining healthy A1c levels, and focusing on eating nutrient-dense foods and a quality nutrition plan, you’re not just protecting yourself from type 2 diabetes complications, you’re also helping to safeguard your memory, your independence, and your quality of life as you age.
For all of us, prevention starts now. Every balanced meal, every walk, every good night’s sleep, they’re all investments in our brain’s future, so keep that in mind with each positive step you take forward.
Thanks so much for tuning in today.
Dr Jedha, over and out.
