By Jerome Burke
Why too much fructose is driving dementia, diabetes and brain fog
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The fruit sugar ‘fructose’ isn’t generally considered a food that’s best avoided. After all, it comes from fruit.
Yet a radical new theory, developed by Richard Johnson, Professor of Nephrology at the University of Colorado, explains how it can trigger various damaging changes in our metabolism that make us more likely to develop chronic conditions such as diabetes, obesity and Alzheimer’s. If doctors better understood this, it could transform the new emphasis on sickness prevention that the government is promising.
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Professor Johnson has produced what is effectively a biochemical wiring diagram of the connections which fructose turns on and off, that are making an increasing number of people sick. Fructose makes up half of white sugar and most of fructose corn syrup which is the main sweetener in fizzy drinks and ultra-processed foods as well as being the main sugar in fruit, particularly fruit juice.
For instance, the amount of fat stored in the liver increases, driving fatty liver disease, while the cell’s mitochondria, which create the body and brain’s energy molecule ATP, become less productive and blood pressure goes up. The result is that you get fatter, with more brain fog and fatigue and feel less inclined to exercise. Fructose is also a major promoter of diabetes.
Meanwhile an anti-ageing process called autophagy, which would normally clear away used up and damaged mitochondria, the cell’s energy factories, to make room for new ones, is disabled. When fructose crosses the blood-brain barrier into the brain, it is one of the factors causing the brain to form the clumps of amyloid protein found in Alzheimer’s, which is the focus of new drug treatments.
Why on earth does fructose carry out such a blitz on our bodies? Why would the body run a programme that was potentially so lethal?
“It would be wrong to think of fructose as some sort of major toxin, although it becomes neurotoxic in excess,” says Professor Johnson. “Instead, its remarkable range of effects are part of an ancient set of biological programs, which we call the ‘Survival Switch’, that work to prepare animals for hibernation, storing supplies in preparation for times of famine.” This is why fat storage increases and energy drops off producing brain fog. The trouble is we never run out of food or fructose in our modern times.
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None of this means that we should avoid fruits, which contain only a small amount of fructose that comes with beneficial fibre that feeds our vital gut bacteria, plus various nutrients. Not so for fruit juice, devoid of fibre. A glass of orange juice is the equivalent of three oranges in terms of fructose, but without the fibre. So, eat your fruit, don’t drink it.
But this does explain why too much blood glucose from regularly eating generous amounts of sugar-laden foods and carbohydrates, is so damaging? The liver turns the excess glucose into fructose with all its knock-on effects. Other substances that can accelerate fructose production are alcohol and salt.
This rise in fructose intake and its presence in processed food makes it all too easy to start piling on the pounds, regardless of how many calories you have cut or how much further you are running. It’s a connection that very few nutritionists or GPs are aware of.
A sign of the widespread damage the Survival Switch can cause is that there are low ATP levels in the brains of people with disorders such as obesity, diabetes, fatty liver disease and Alzheimer’s. Understanding this points to new ways to cut the risks of these chronic disorders. Adenosine triphosphate (ATP) is a molecule that stores and provides energy for cells. It’s a key biomolecule that’s involved in almost all cellular processes.
A simple, but very effective solution, is to run a blood test – HbA1c – the gold standard test GPs use to screen for diabetes. HbA1c is a test that measures your average blood sugar level (glucose) over the past two to three months. A recent study of 374,021 older men with diabetes found that keeping the level of HbA1c stable at an optimal level over a period of three years cut risk of dementia by a third. Similar benefits have been found with patients with pre-diabetes (Prediabetes means that your blood sugars are higher than usual, but not high enough for you to be diagnosed with type 2 diabetes. It also means that you are at high risk of developing type 2 diabetes.) But far lower levels of HbA1c than those used to diagnose diabetes are associated with the first signs of brain shrinkage, which is the hallmark of cognitive decline, even in teenagers.
That is why we offer, as part of our ‘citizen science’ research, an at home pin-prick test of HbA1c, to find out not only who is at risk, but also how to reverse that risk. It also works alongside the free Cognitive Function Test that calculates your future Dementia Risk Index and suggests various lifestyle and nutrition changes to help reduce it, including a low fructose diet (Find out more about low fructose foods here).
We also recommend increasing omega-3 intake from oily fish, increasing B vitamins, especially B12, as well as an active lifestyle, as part of COGNITION, our personalised 6-month programme. In this programme we also dive deeper into lowering your ‘glycaemic load’ (GL), which is low in fructose, alongside periods of time of eating in a ‘ketogenic’ way by keeping sugar and carbohydrates to a minimum. The body responds by creating ketones, energy packets that can replace glucose as an energy source for the brain, helping to undo the damage.
(You get access to COGNITION when you become a FRIEND of Food for the Brain here)
‘Burning ketones can also increase the number and output of the cell’s energy factories, known as mitochondria, which are damaged by fructose,’ says Professor Robert Lustig of the University of California, author of the best-selling book Metabolical and who sits on our Scientific Advisory Board. You can read more in his detailed article here.
Both Professor Johnson and Professor Lustig are also part of the Alzheimer’s Prevention Expert Group who have written to UK dementia prevention authorities to add sugar, and specifically a high fructose diet, to the list of known risk factors.
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This low fructose approach also naturally promotes the enzyme GLP-1, targeted by the weight loss drugs Ozempic and Wegovy, but without the side-effects or rebound weight gain.
Our founder Patrick Holford says: “Today’s typical diet of burgers, carbonated drinks, fruit juice, ice cream, bread, biscuits, cakes and confectionery, plus alcohol and salt, is a dementia time-bomb. Our brains are literally being ‘fructed’. We see the same shrinkage in the same regions of the brain in teenagers with a high sugar intake that are seen in older Alzheimer’s patients. We think of the resulting dementia as type-3 diabetes.”
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Thank you for reading!
Food for the Brain is a non-for-profit educational and research charity that offers a free Cognitive Function Test and assesses your Dementia Risk Index to be able to advise you on how to dementia-proof your diet and lifestyle.
By completing the Cognitive Function Test you are joining our grassroots research initiative to find out what really works for preventing cognitive decline. We share our ongoing research results with you to help you make brain-friendly choices.
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