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The Hidden Influence of Blood Sugar on Brain Health

How does blood sugar impact the brain?

By Austin Perlmutter, MD



  • High or low blood sugar levels are well known to create brain problems

  • Many people have poor metabolic health which includes trouble regulating blood sugar, long before they develop diabetes

  • Research shows links between diabetes, depression and dementia

  • Many lifestyle changes may help people with metabolic health, and those with significant issues with their blood sugar are likely to benefit from personalized care

We often hear about the importance of stable blood sugar levels for our health, especially when we are talking about diabetes management. But the link between blood sugar and brain health may be just as important, and it is all too often missed. To keep you thinking clearly (or even thinking at all), your brain needs a constant supply of its main fuel source, glucose. Here’s why blood sugar matters so much for brain health, and what to do about it.

What fuel is my brain running on anyway?

Compared to other parts of the body, the brain requires a disproportionately high level of fuel. In fact, it’s often stated that the brain uses up around 20% of our blood sugar, even though it’s only around 2-3% of our weight. Convincing research demonstrates the importance of a “goldilocks” level of blood sugar to keep the brain functioning well, since high blood sugar and low blood sugar can both lead to rapid and disastrous brain issues. Quick note: the brain can also use ketones for fuel, but for most, this does not factor into major daily energy needs for the brain.

How does blood sugar relate to conditions like dementia and depression?

Depression and dementia affect hundreds of millions of people around the world. In both cases, research is still ongoing as to exactly what is driving the diseases. Yet many scientists have recently been exploring the link between blood sugar levels and risk for these conditions. In a recent review of 144 studies, having problems managing blood sugar (like prediabetes and diabetes) was linked to a higher risk for cognitive impairment and dementia. A recent review of over 100,000 individuals in China found that diabetes was linked to a 25.9% chance of having depression (36% in women). All in all, research has shown that people with consistently unstable blood sugar are at higher risk for brain conditions.

Why are blood sugar imbalances linked to worse brain health?

Several pathways have linked blood sugar issues with worse brain health outcomes. Many specifically relate to the effects of sustained high blood sugar. Some of these mechanisms include higher levels of inflammation, more oxidative stress, damage to blood vessels and hormonal imbalances (insulin, for example, has many important roles in brain health, including promotion of neuroplasticity). Research has shown this may be most relevant for people with diabetes, but with most people today experiencing some form of metabolic dysfunction, this is information we should all consider.

How can we help promote healthier blood sugar levels to help protect the brain?

By and large, the most important steps for people without diabetes to promote healthy blood sugar have to do with lifestyle variables. Here are the basics:

  • Regular exercise is known to positively impact blood sugar stability. It also seems to have an especially positive effect on brain energy metabolism.

  • Eating a balanced diet low in ultraprocessed foods with added sugars and high in whole, real foods may help regulate healthier blood sugar levels.

  • Stress revs up cortisol, which may damage blood sugar balance. Finding ways tomitigate chronic stress may therefore help keep blood sugar levels more stable.

  • For those with diagnosed diabetes or significant concerns about blood sugar, it’s important to follow the recommendations of your practitioner.

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