Is your brain safe from sugar?

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Back in 2013 (when this post was first published), it was quite fashionable to ‘quit sugar’. 

Health and well-being messages have moved on in the past decade, but limiting refined sugar is still a wise choice.

Here in Australia, we’re reminded that eating a diet high in added sugar can lead to a person becoming overweight or obese, increasing the risk of type 2 diabetes and some cancers and stroke.

Diabetes is linked to poor brain health.

Diabetes, especially type 2 diabetes, is not the cause of dementia, rather, it is a risk factor for dementia.

Using language we’ve become used to hearing since the COVID pandemic: dementia is a comorbidity of type 2 diabetes.

To put the information into numbers: people with diabetes have a 1.4-2-fold increased risk for developing Alzheimer’s disease. 🌱

And if you have diabetes, you’re also at greater risk for general cognitive decline as you age. 🌱

Scientists are still unravelling the exact molecular pathways and mechanisms that link diabetes and dementia, but it’s most likely a combination of the effects of insulin resistance, vascular pathology, oxidative stress, glucocorticoid excess and inflammation. 🌟

Not too worried because you don’t have diabetes? Well, hold back on that chocolate…

You don’t need to have diabetes to be at risk of dementia.

Higher blood sugar levels are associated with higher dementia risk, even among people who do not have diabetes 🌱

A 2013 report in the New England Journal of Medicine followed 2000 over-65-year-olds for five years in the Adult Changes in Thought (ACT) study. The participant’s blood sugar levels were taken 17 times and averaged out over the course of the study.

The finding was clear: high blood sugar levels were associated with an increased risk of developing dementia.

  • In people WITH diabetes, dementia risk was 40% higher for people with an average glucose level of 190 mg/dl than those with an average glucose level of 160 mg/dl.
  • For people WITHOUT diabetes, those with an average glucose level of 115 mg/dl were compared to people with an average glucose level of 100 mg/dl (normal is 70-100 mg/dl).  The higher blood sugar group had an 18% higher risk of developing dementia. 🌱

Associate Professor Paul K. Crane, one of the authors from the University Washington School of Medicine, said,

“What we found was that people with higher levels of glucose had a higher risk of dementia, on average, than did people with lower levels of glucose …

There was no threshold value for lower glucose values where risk levelled off.”

Paul K. Crane

Rather depressingly, the authors reported that they have not yet found evidence that dementia risk could be lowered even if people ate less sugar.

 “Your body turns your food into glucose, so your blood sugar levels depend not only on what you eat but also on your individual metabolism: how your body handles your food…

While that is interesting and important, we have no data to suggest that people who make changes to lower their glucose improve their dementia risk.” 🌟

Paul K. Crane

It’s not all bad news.

Professor Crane and the ACT study group have previously found that exercise lowers the risk of dementia developing (as have numerous other studies). 


It turns out exercise is one of the best ways to regulate your blood sugar levels and prevent the development of diabetes. 🌱

2023 Research Updates

🌱 New Updates 🌱

🌱 New research published in 2022, has shown that brain ageing speeds up by 26% in people with type 2 diabetes. The most dramatic change occurs in parts of the brain critical for learning, decision making and other executive functions.

🌱 The relationship between glucose levels and Alzheimer’s disease is seen in adults as young as 35. In a 40-year study, elevated blood glucose levels in healthy people from age 35 onwards increased Alzheimer’s disease risk. Once study participants reached middle age, every 15 mg/dL increase in blood glucose caused a 14.5% increased risk of Alzheimer’s disease.

🌱 The people within the higher blood sugar group in this ACT study could also be labelled as having prediabetes. Further research has now shown that middle-aged people with prediabetes have a similar rate of cognitive decline as those with diabetes. Prediabetic people were also found to be 54% more likely to develop vascular dementia over an 8-year period than healthy individuals.

🌱 Experiencing a physically and cognitively active life can significantly reduce dementia risk, even if you don’t have diabetes. But interestingly, active older people with diabetes have a similar dementia risk to highly active individuals without diabetes. Meanwhile, inactive people with diabetes have a nearly 30% greater risk of dementia compared to diabetic people with active lifestyles. In short: staying active matters!

🌟 Important New Research 🌟

🌟 One interesting mechanism that likely links Alzheimer’s disease to diabetes is the accumulation of a protein called amyloid-beta. Build-ups of amyloid-beta within the brain are a known contributor to Alzheimer’s disease. This protein is also immediately released into the bloodstream in response to increased glucose and insulin by other organs, like the pancreas and liver.

The higher glucose and insulin levels in people with diabetes mean that the level of amyloid-beta in the blood is more consistently raised. Increases of this protein within the blood can prevent it from being removed from the brain at blood vessels. Increased insulin also prevents any excess amyloid-beta in the brain from being broken down and detoxified. This can all cause an accumulation of amyloid-beta in the brains of people with diabetes which could increase their risk of later developing Alzheimer’s disease.

🌟 Though controlling glucose with diet can be difficult, emerging research suggests that taking diabetes medications can protect against dementia. Unmedicated diabetic people develop Alzheimer’s disease six times faster than people who don’t have diabetes. Meanwhile, people who are medicated for their diabetes develop dementia at a similar rate to non-diabetic individuals.

🌟 The Sydney Memory and Ageing Study found older people who treat their type 2 diabetes with the anti-diabetic drug metformin experience slower cognitive decline and decreased rates of dementia.

However, the lead researcher of this study Professor Katherine Samaras believes that metformin may additionally protect non-diabetic people at greater risk of dementia:

“This study has provided promising initial evidence that metformin may protect against cognitive decline. The intriguing question is whether metformin is helpful in people in those with normal glucose metabolism. We are now planning a large, randomised controlled trial of metformin in individuals at risk of dementia and assess their cognitive function over three years. This may translate to us being able to repurpose this cheap medication with a robust safety profile to assist in preventing against cognitive decline in older people.”

Professor Katherine Samaras

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  1. Babs Philbin on March 7, 2014 at 7:57 pm

    I might well be addicted to sugar, certainly have a sweet tooth, so no, I have never tried to quit as it seems impossible. Even when I try to make healthier food choices like fresh, often green juices, there is a lot of sugar in them, although a healthier kind I am led to believe. I am trying to find alternatives to the sweet things I like, creating similar things, like chocolate spread, on a more plant based level, but obviously it’s not quite the same. I do use Stevia as a sweetener as well. And when I do have refined sugar I often have cinnamon with it in order to keep my blood sugar levels low.

  2. […] Source: Yourbrainhealth […]

  3. Peter on April 22, 2016 at 12:15 pm

    A bit like you Sarah, I have minimised the refined and processed stuff, and upped the Mediterranean goodies. Haven’t cooked with sugar (or honey, * syrup, stevia, etc.) for ages. If I want sweetness, I use fruit, either fresh or dried. I figure that way at least I get some other nutrients at the same time – could be some fibre, vitamins, minerals. Sugar has nothing. For my chocolate fix, it’s a couple of squares of dark chocolate each night. I seem to have settled on 85% cocoa – that way it can’t have any more than 15% sugar. I was surprised how quickly (couple of weeks) after reducing my sugar intake that previously ‘normal’ treats tasted too sweet for me. Bonus!

  4. Adele Stewart on February 2, 2023 at 7:29 am

    I’m all for reducing sugar in the diet but basically this article is not saying that sugar is bad for the brain , but that diabetes is bad for the brain. Dietry sugar is only tiny part of keeping a healthy weight. Perhaps 10 years on the article needs a name change?

    • Sarah McKay on May 15, 2023 at 9:46 am

      Great point. We’re in the process of updating our most popular blogs. So stay posted!!

  5. Angela Davies on February 2, 2023 at 8:16 am

    soooooo loved sugar, sweets icecream; Took years to succeed now none, occasionally 2 squares 99% 95% lindt chocolate. cinnamon and Pur cinnamon chewing gum everyday helped. jasmine green tea nullify sweet urge. fill up on satiating Mediterranean style diet thus no room for sugary food. fruits an apple with decaffeinated coffee at afternoon picks me up. Exercising boost my mental and physical physiology while making me feel much better than if I didn’t do it (works like magic everytime).

  6. Elizabeth Leighton on February 3, 2023 at 7:55 am

    I’m over 82 and have always exercised every day to keep my slim & healthy body as fit as possible. I also work at learning French every day, hoping to slow/prevent dementia. I’m convinced that my physical and mental exercise is absolutely essential for my well-being. Restricting sugar is an enormous challenge, but I know from personal experience it’s crucial.

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