If your memory is getting worse, it’s likely not simply your age. What actually happens to the brain when blood sugar runs elevated for 10 to 20 years tells a very different story — and understanding it early matters, because by the time memory symptoms show up, the underlying problem has usually been developing for a long time already. (Based on the insights of Dr. Eric Berg)
Key Takeaways
- Memory loss and dementia are described here as progressing through four stages, with brain changes beginning long before symptoms appear.
- A PET scan can reveal glucose hypometabolism in the brain years before standard testing would catch anything — part of why Alzheimer’s is sometimes called “type 3 diabetes.”
- Chronically high blood sugar and insulin depletes vitamin B1 (thiamine) through urine at 16–24 times the normal rate.
- The National Institute on Aging is running a Phase 2 trial on benfotiamine (a form of B1) for Alzheimer’s across 50 sites.
- Reducing refined carbohydrates and sugar is described as the most important single action, since diet directly affects how much B1 is available.
The Four Stages Before Memory Loss Becomes Obvious
Stage one involves an energy drop in the brain. Memory is still good at this point, with few or no symptoms beyond maybe some fatigue.
Stage two is when certain protein residues start building up in the brain without being properly cleared, and the hippocampus — the part of the brain responsible for memory — begins shrinking. The hippocampus is a genuine energy hog, containing the densest concentration of mitochondria (the brain’s energy factories) of any brain region, so it requires significant energy to function. Memory is still generally fine at this stage.
Stage three is when things start becoming noticeable — particularly trouble remembering names, and a decline in the ability to learn new things. This can begin as early as someone’s 30s or 40s.
Stage four is typically when diagnosis happens, in part because a person starts losing the ability to notice their own cognitive decline — often family members notice the memory issues before the person does.
Why Standard Testing Misses This Early On
Traditional medical testing tends to be symptom-focused, so if there are no symptoms yet, testing typically doesn’t happen. The test that can catch this earlier is a PET scan — the same type of scan used in cancer detection, though for a very different reason. In cancer, a PET scan looks for areas of high glucose uptake, since cancer cells consume glucose aggressively. In Alzheimer’s and other forms of dementia, it’s the opposite: a hypometabolism of glucose shows up, meaning the brain is taking up less glucose than it should.
This is part of why some researchers refer to Alzheimer’s as “type 3 diabetes” — it’s fundamentally an energy problem. When glucose levels running through the bloodstream stay elevated for a long time, the body compensates by reducing glucose uptake, a process called insulin resistance — and this can happen in the brain specifically. The result is plenty of glucose in the bloodstream, but much of it becomes unavailable to the neurons that need it.
Three Questions to Ask Yourself
1. Do you need to eat every two or three hours to avoid getting irritable or foggy? This is a meaningful indicator of a blood sugar issue, even without a diabetes diagnosis, since these problems often take years to become measurable through standard testing.
2. Do you wake up between 2 and 3 a.m. for no clear reason? This is often a blood sugar issue rather than a stress or cortisol problem.
3. Do you feel mentally sluggish or need a nap after a high-carbohydrate meal? If you answered yes to any of these three, it may indicate you’re somewhere along this progression.
The Role of Vitamin B1 (Thiamine)
When glucose and insulin levels run high for extended periods, the body loses vitamin B1 through urine at a rate 16 to 24 times higher than normal. In other words, the more refined carbohydrates consumed, the more B1 gets depleted.
This matters because of a backup energy pathway called glycolysis, which provides only a small amount of fuel compared to what mitochondria can generate when functioning properly. In diabetes, cancer, and Alzheimer’s, the mitochondria themselves aren’t necessarily damaged — it’s more like the entry door into that energy factory is blocked. B1 is essential for keeping that door open. Without it, the body generates excess lactic acid — which is exactly what’s been found in the brains of people with Alzheimer’s, and this buildup reduces oxygen availability and compounds the problem further. Picture an engine: oxygen and fuel need to mix properly, but you also need a spark plug to ignite it — B1 functions like that spark plug.
Ongoing Research on Benfotiamine
Researchers are currently studying a specific form of B1 called benfotiamine in relation to Alzheimer’s. The National Institute on Aging is running a large Phase 2 trial testing benfotiamine across 50 different sites. Benfotiamine is already used for peripheral neuropathy in type 2 diabetes, and it’s known to help clear out toxic glucose byproducts and support regeneration of the myelin sheath, the protective coating around nerves.
The core issue driving B1 deficiency for most people is simply consuming too many refined carbohydrates. Refined wheat and grains, for example, lose more than 85% of their natural B1 content during processing. Eating a diet high in refined carbohydrates, sugar, and starch creates an ongoing B1 deficit that keeps shutting the door to that primary energy pathway, forcing the body to rely on the much less efficient backup system — which is part of why fatigue becomes such a common symptom.
What Actually Matters Most
Regardless of where someone is in this progression, reducing refined sugars and carbohydrates is described as the single most important action to take — because no amount of B1 or benfotiamine supplementation can outpace a diet that keeps depleting it. The suggestion here is to pair a low-carbohydrate diet with benfotiamine supplementation, since the low-carb approach protects the B1 you’re taking in rather than letting it get consumed as fast as it’s replenished. Adding intermittent fasting is described as another way to accelerate progress, since addressing Alzheimer’s or dementia risk fundamentally requires addressing the underlying blood sugar problem.
Frequently Asked Questions
Why is Alzheimer’s sometimes called “type 3 diabetes”?
Because PET scans show a hypometabolism of glucose in the brains of people with Alzheimer’s — the opposite of what’s seen in cancer, where glucose uptake is high. This pattern points to an underlying energy and insulin resistance problem specific to brain tissue.
Why does eating refined carbohydrates deplete vitamin B1?
High blood sugar and insulin levels increase B1 loss through urine substantially, and refined grains themselves lose more than 85% of their natural B1 content during processing — creating a double depletion effect.
Is benfotiamine supplementation enough on its own?
According to this approach, no — supplementing B1 without reducing refined carbohydrates isn’t effective, since continued high carb intake keeps depleting the B1 as fast as it’s replenished. A low-carb diet is described as necessary alongside supplementation.
What are simple signs that blood sugar might be affecting brain energy?
Needing to eat every 2–3 hours to avoid irritability or brain fog, waking up between 2–3 a.m. for no clear reason, and feeling mentally sluggish or needing a nap after high-carb meals are three signs discussed here.
Quick Start Checklist
- ☐ Ask yourself the three questions about eating frequency, 2–3 a.m. waking, and post-meal sluggishness
- ☐ Reduce refined sugars, starches, and processed carbohydrates
- ☐ Ask your doctor about a PET scan if cognitive changes are a concern
- ☐ Discuss benfotiamine supplementation with your doctor before starting
- ☐ Consider a low-carb approach alongside supplementation, with medical guidance
- ☐ Talk to your doctor before exceeding label-directed supplement doses or starting intermittent fasting
Source: Dr. Eric Berg
Disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Supplement dosing recommendations in the source material go beyond standard label directions and are not based on an established clinical protocol; consult your doctor before starting benfotiamine or any new supplement, especially at doses above label directions, and before making significant dietary changes like low-carb eating or intermittent fasting, particularly if you have diabetes or take related medication.