Is Sugar Killing Your Brain?

Sugar and our now standard high-carb diets are a major health problem. To put this in context, more people have died from diet-related diseases, primarily driven by high sugar, ultra-processed foods and refi ned carbohydrates, than in the First and Second World Wars combined.

Most people know that refined sugar is not good for us, but what is it about sugar that’s particularly bad for our brain?

My go-to guy on issues of sugar and mental health is Dr Robert Lustig, Professor Emeritus of Paediatrics in the Division of Endocrinology and a member of the Institute for Health Policy Studies at the University of California, San Francisco. He is also a paediatric neuroendocrinologist and an international authority on obesity, diabetes, nutrition and neuroscience. He’s our ‘sugar man’ on the Scientific Advisory Board at Food for the Brain.

I asked Dr Robert Lustig, ‘Why is it essential, not only for brain health at every stage of life but also dementia prevention, to reduce your intake of not only sugar but refi ned carbohydrates in general?’ (By ‘refined’, I mean those carbohydrates whose fibre has been processed away, leaving them looking whiter, not ‘whole’.)

‘Let’s start at the extreme,’ he replied. ‘What would happen if you lived at the North Pole, and ate virtually no carbohydrates, or at least so few as to force your body and brain to switch to ketones, a kind of fuel produced from fat? This is often called  a “very low-carb, high-fat (LCHF)” or “ketogenic” diet. Would you get sick? This is how V ilhjamur Stefansson lived when his Arctic exploration party was shipwrecked in 1913 and he was forced to live among the Inuit for two years. He noted that there was no diabetes there, no cancer – and no Alzheimer’s. In 1928, he and his colleague checked themselves into Bellevue Hospital in New York and ate only meat for one year. By the end of it, they were healthier than the researchers who studied them!’

Sugar Damages the Brain

Blood glucose levels in the low–normal range are reflected by a low blood glycosylated haemoglobin (HbA1c) level, which means ‘sugar-coated red blood cells’. If your doctor suspects you might be heading for diabetes, they’ll measure your HbA1c level, because if over 7 per cent of your red blood cells are ‘glycosylated’ or sugar damaged, that diagnoses you as diabetic. Having a level above 6.5 is considered pre-diabetic, but really you want your level to be below 5.5. (In the UK this is now measured differently, with 75 nmol/mol as high and below 41 nmol/mol as optimal.) Teenagers with an HbA1c above 5.4 show brain shrinkage and cognitive decline similar to that seen in dementia.75 The youngest non-genetic dementia diagnosis is that of a 19-year-old man in China. A low HbA1c is good and is a proxy for insulin sensitivity, which has been associated with a reduced risk of dementia in several studies.76

Type 2 diabetes, the net result of losing blood sugar control, almost doubles the risk of dementia.77 Diabetes is also associated with more rapid brain shrinkage.78 Even people in the upper normal blood glucose range have increased brain atrophy, impaired cognition and increased risk of dementia.79

For instance, one trial measured HbA1c and glucose levels in several thousand elderly people over the course of almost seven years. In that time, slightly more than a quarter of the participants developed dementia, and the bottom line was that rising glucose levels were associated with increased risk of developing the condition, irrespective of whether the participants also had diabetes. Non-diabetics who experienced a modest increase in blood sugar levels had an 18 per cent increased risk of dementia, as compared with those who already had diabetes at the start of the study or developed it within the trial period, who had a 40 per cent increased risk.80

Insulin Resistance is strongly Related to Cognitive Decline

Dr Lustig considers that the loss of insulin control is even more important than the loss of glucose control. Back in 2004, researchers at Columbia University showed that people with high insulin levels – the principal hallmark of metabolic dysfunction – were twice as likely to develop dementia as those with healthy levels. Moreover, those with the highest insulin levels had the worst memory retrieval. The same year, an Italian study established a link between heightened insulin levels and declining mental function. Similarly, a Puerto Rican study found that people who consumed large amounts of sugar doubled their risk of suffering poor cognitive function, while another US study discovered a strong correlation between blood sugar level and memory loss.

Two studies – one in Ireland and the other in the United States – established a link between high dietary glycaemic load (GL) and cognitive decline. (GL is the measure of the total glucose load on your bloodstream, which is both how high your blood glucose rises and for how long when you eat carbohydrate.) Indeed, both of these reports suggest that high GL is even more predictive of the pathological changes associated with Alzheimer’s than either high carb or high sugar intake. A high-GL diet is also associated with more amyloid plaque87 and more cognitive decline, especially in those who carry the ApoE4 gene, which helps regulate fat metabolism.88

A long-term study found evidence that this sort of shrinkage is more common among people with high blood glucose levels, even when those levels are still within what are considered ‘normal’ (i.e., non-diabetic) limits.

‘This cognitive decline starts young,’ says Lustig. ‘Cognitive decline in overweight children is associated with a high-GL diet,90 and adolescents with metabolic dysfunction driven by a high-GL diet have been shown to have shrinkage of the hippocampal area of the brain, as well as other structural changes and cognitive defi cits.’91

This particular study showed actual shrinkage of the Alzheimer’sassociated area of the brain in teenagers with metabolic syndrome as a consequence of too much sugar and ‘white’ carbs.

Preventative Action – How to Cut Down Your Sugar Load

One of the most obvious indicators that your sugar and/or carb intake is too high is weight gain. Another is sugar cravings. In practical terms, protecting your brain and preventing dementia means avoiding sugar as much as possible. You could even go one step further and go ketogenic (see the next chapter). If you’re going to eat carbohydrates, eat ‘whole’ carbohydrate foods such as whole vegetables, fruits (not juice), beans, only wholegrain bread (labelled as ‘100 per cent wholegrain’), or pasta in small quantities.

Starchy carbohydrates such as pasta, rice and potatoes benefit from being cooked and cooled, then eaten cold or reheated, as that way some of the carbohydrate is converted into resistant starch – a type of fibre we can’t digest but which has the added benefit of fermenting and feeding our gut bacteria.

Make sure the carbohydrate comes with its inherent fibre. Oatcakes would be better than bread, since the fi bre helps ‘slow release’ the sugars. Eating white bread is associated with a poorer cognitive test performance, whereas high-fibre bread is associated with better performance.92 The less squishy, more solid a loaf, the lower its GL. Eating carbohydrate foods with protein, for example brown rice with fish, or porridge oats with seeds, or fruit with nuts, further reduces the glycaemic load. The best fruits in this respect are low-sugar, high-fi bre fruits like berries, cherries and plums.

These kinds of foods are consistent with a Mediterranean diet, which has also been shown to reduce risk. Conversely, grapes, raisins and bananas are high-GL.

A study in Finland and Sweden compared those with a healthy versus unhealthy diet, including the above criteria, in midlife for the risk of developing Alzheimer’s disease and dementia 14 years later. Those who ate the healthiest diet had an 88 per cent decreased risk of developing dementia and a 92 per cent decreased risk of developing Alzheimer’s disease.

The take-home message is, if you are going to eat complex carbohydrates, eat them with fibre, fat and protein.

Prevention Action Steps

  • Sugar, and especially high-fructose corn-derived sugar, damages the brain.
  • Too much sugar and too many refi ned carbohydrates, and carbohydrates in general, leads to insulin resistance, which starves the brain of fuel, leading to cognitive decline.
  • The best way to measure your sugar status is an HbA1c blood test, with the goal to be below 5.4 per cent, ideally around or below 5 per cent. (See page 316 for more on testing.)
  • Nature never provides sugar, as in fruit, without fi bre, so eat your fruit, don’t drink it.
  • A low-carb diet is brain-friendly.

What Next? Upgrade your Brain AND Become a Citizen Scientist

Thanks to already well over 400,000 ‘citizen scientists we have, with the sword of digital technology, opened the oyster to uncover the true causes – all under your control – that are driving this terrible and unnecessary brain shrinkage.

Those citizen scientists have taken the time, often initially for personal interest, to discover their actual cognitive function, and completed a comprehensive questionnaire.

We hope to reach a million people around the world within a year or so making this the biggest prevention-focussed study of its kind.

Change is not going to come from the Government or the NHS. It is going to have to come from us, the people.

We ask you to take control of upgrading your brain and in the process become Citizen Scientists for better brain health for future generations.

Follow these seven steps.

STEP 1: Take the Cognitive Function Test

What you’ll learn:

  • Find out where you are on the cognitive function scale
  • Learn the most important dietary and lifestyle actions you can take
  • Take control of your mental wellbeing
  • Contribute to the Food for the Brain research process

Take the Cognitive Function Test

STEP 2: Test for the Four Keystone Biochemical Processes

A consensus of world experts concluded that lowering homocysteine with B vitamins is the easiest and most cost effective prevention action, which Oxford University’s health economists estimate would save the UK £66 million per year.However, it’s vital to test both homocysteine and Omega-3 levels, as they are co-dependent. Homocysteine-lowering B vitamins only work in those with sufficient omega-3, and omega-3 only works if homocysteine is low.

So, get tested for the four keystone biochemical processes with the DRIfT Test.

It will calculate your Dementia Risk Index functional Test (DRIfT) score. Tracking this, along with your Cognitive Function (CFT) and Dementia Risk Index (DRI) is the most comprehensive way to protect your brain.

This 4-in-1 test measures:

  • Vitamin D
  • Omega-3
  • Homocysteine
  • HbA1C

More info – Drift Test from Food for the Brain and Other Tests.

STEP 3 – Get Educated

Read my book Upgrade Your Brain – Out Now!

More info & to order – Upgrade Your Brain Book

Join me on my UK or Ireland Seminar Tour – May/June

I’m visiting 30 cities in the UK and Ireland in May/June to kick start a nationwide ‘Upgrade Your Brain’ campaign.

“We need to engage with millions of people, get nutrition education happening in schools, and most of all get heath authorities and governments around the world to take the mental health meltdown seriously and put brain health at the top of the health agenda.”

Professor Crawford says “Today’s diet bears no resemblance to the wild foods we ate during our species’ evolution to which our genome is adapted. If we don’t prioritise brain health and nutrition the continued escalation of mental ill health, starting in the 1950s, can only end in disaster.”

Dates/locations: More tour info & how to book

Sign up to my E-News

Go to the home page of this website and sign up to my E-News for more blogs/reports/videos and podcasts on brain health. Follow on Facebook (PatrickHolford) and Instagram. (PatrickHolford.UK)

STEP 4: Start a Brain Healthy Diet

The Upgrade Your Brain cooking app with brain-friendly recipes will be launching soon. It will help you make the right food choices for your brain.

Pre-order the Brain Cook App. 

STEP 5: Ensure You Get Enough of the Right Nutrients

There are three essentials for building brain cells (neurons) – omega-3 fats, B vitamins and Phospholipids. Omega-3 is bound to phospholipids by methylation which is a process that is dependent on B vitamins – B6, B12 and folate.

There are some key supplements that have been identified to support brain health. In the Holford range these are:

  • Connect: B vitamins and zinc to support healthy methylation
  • High PC Lecithin – A Rich source of 63% phospholipid
  • Omega-3 Support – 550mg of DHA and 750mg of EPA

All these are found in the Brain Food Upgrade pack

STEP 6: Spread the Word & Promote Prevention

We urge everyone to share the ‘prevention’ message with others.

You can do this by sharing social media posts and blogs/reports.

You can participate in Alzheimer’s Prevention Day on 15 May and encourage others to do the same. Take the free 3-minute online Alzheimer’s Prevention Check and get motivated to make the eight brain-friendly diet and lifestyle changes

“You are the architect of your own brain’s future health.” says neurologist Dr David Perlmutter.

Take the test for Alzheimer’s Prevention Day

Step 7: Support the ‘Prevention’ Work

‘Friends’ donate £50 a year and get so much in return. This is how we are funding our amazing research team (see We are a lean, keen, small but mighty team.

Every donation, big or small, goes right back into helping people prevent these preventable and terrible diseases such as dementia. Together, we can change the world. We need to, because time is running out. We will lose our humanity if we don’t stop this brain drain.”

All donations are put back into research, and the results of the research are shared back to people.

Give to Food for the Brain and support their work.