Study suggests that cutting back on sugar and starch may preserve mental functioning as we age

I suspect many individuals dread the idea of losing their mental faculties as they age. I think nutrition probably plays a very important role in how well the brain ages and how well its functioning is preserved. This week saw the on-line publication of a study that suggests that a key factor here may be good ‘glycaemic’ control.

While we do not want blood sugar levels to be too low, we do not want them too high, either. Abnormally elevated blood sugar levels is a hallmark feature of diabetes. One of the risks here is that glucose can bind to and damage tissues through the process ‘glycation’, and this can lead to a variety of complications for diabetics including nerve, kidney, blood vessel and eye damage.

One of the ways doctors can assess broad blood sugar control is through a test known as the ‘HbA1c’ (also known as the ‘A1c’, or ‘glycated haemoglobin’ or ‘glycosylated haemoglobin’). This test measures the amount of the protein haemoglobin in the red blood cells that is bound up with glucose. Basically, higher levels of HbA1c signal poorer blood sugar control.

In this week’s study, the relationship between brain structure and function and HbA1c levels was assessed in a group of non-diabetics. Higher HbA1c scores were found to be associated with smaller regions in the brain known as the ‘hippocampus’ (a part of the brain involved in memory). Those with higher HbA1c levels performed generally worse in tests of memory and learning.

In recent years, there has been growing interest in the relationship between blood sugar control and Alzheimer’s disease. Some researchers have suggested that at least some cases of this condition are due to what is being terms ‘type 3 diabetes’ – essentially, a mix of insufficient insulin (a feature of type 1 diabetes) with poorly functioning insulin (a common feature of type 2 diabetes).

Raised blood glucose levels might perhaps damage the brain through several mechanisms. Glycation is one. Also, though, raised blood sugar is inflammatory in nature, and inflammation in a potential underlying factor in deteriorating brain function over time.

Another mechanism that may be relevant here concerns cholesterol. Cholesterol is highly concentrated in the brain, where it performs several functions. It’s critical, for instance, to the function of the synapse (the ‘gap’ where one cell can communicate with another), and also has a role as an electrical insulator and as a structural ‘scaffold’ in the brain. Cholesterol is also a functional component of all cell membranes in the brain [2]. Higher levels of glycation (through higher blood sugar levels) can impair cholesterol uptake into the brain, potentially starving this organ of a component critical for its proper functioning.

What is perhaps interesting about this week’s study is that the relationship between improved blood sugar control and better brain function was found in non-diabetics. This throws up the possibility that scaling back on blood sugar disruptive carbohydrates such as those rich in sugar and starch could well be a good tactic for those of us wishing to preserve their mental functioning as they age, whether we have diabetes or not.


1. Kerti L, et al. Higher glucose levels associated with lower memory and reduced hippocampal microstructure. Neurology, 23 October 2013

2. Seneff A, et al. Nutrition and Alzheimer’s disease: The detrimental role of a high carbohydrate diet Eur J Int Med 2011;22:134-140

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11 Responses to Study suggests that cutting back on sugar and starch may preserve mental functioning as we age

  1. Kevin eakins 25 October 2013 at 10:24 am #

    This study points to the fact that for every person with overt chronic disease there are maybe two to three times as many more people out there with the “pre-” condition or disease which is is slowly (or not so slowly as the case may be) turning into the full blown pathology.

    In this case its diabetes versus insulin resistance. Maybe up to one third of the population in societies consuming “typical Western, processed food diets” can be lumped into one of these two categories with the majority in the latter. It should be remembered that this is across all age groups.

    The point is that sugars and simple/processed carbohydrates are metabolic poison for all of us. Some of us can withstand the assault for a lifetime but most can’t. The longer we are exposed to the poison, the more likely it is that we will succumb.

    This is not to say that the odd dessert is out of the question or that we need to get obsessed about it. However we all need to be concious every day that there are good food choices and bad and that discerning between them is critical to the long term health of all of us.

  2. Stuart Ward 25 October 2013 at 10:49 am #

    My Grandad died of Alzheimer’s 5 years ago and i saw first hand how hideous and cruel this disease can be.

    I’m currently reading grain brain by David Permutter and he talks of the same problem.
    A food we are not used to is going to upset the body and mind as both work together.

    I remember reading about a study done around 100 years ago by Russian researcher Nikolai Anitschkov. He feed rabbits high fat diets and their arteries thickened and filled up with cholesterol. I’m sure if he looked deeper there would have been many more metabolic problems with those rabbits. I guess we are the same its just our excessive poison is sugar and wheat.

    Lets hope this research continues and is acted on.

  3. William L. Wilson, M.D. 25 October 2013 at 12:49 pm #

    Yes this a very interesting article. There are two other ways that sugar might impair brain function. High levels of glucose can impair mitochondrial function:

    Hyperglycemia also appears to cause some degree of neurotransmitter dumping, eventually leading to a depletion of neurotransmitters:

    Hyperglycemia has also been shown to increase brain damage in those with strokes. Thus it appears that high glucose levels are not so good for your brain. It’s also important to look at the types of foods that raise glucose levels. Excessive fructose from sugar and HFCS leads to insulin resistance and when you have insulin resistance and consume high glycemic carbohydrates your brain is subjected to magnified glucose spikes. Excessive omega six fatty acids from vegetable oils likely contribute to hyperglycemic because they are pro-inflammatory. These three dietary components describe typical processed food.

    David Perlmutter describes how processed foods can act as secondary triggers to a long list of brain disorders in his new book “Grain Brain”. We now also believe that this type of food can directly lead to a form of food-induced brain dysfunction called Carbohydrate Associated Reversible Brain syndrome or CARB syndrome. One of the symptoms of CARB syndrome is cognitive dysfunction and this article is supportive of the CARB syndrome concept.

  4. Diane 25 October 2013 at 4:03 pm #

    It seems that the dietary advice we have been given over the last 30-40 years to eat lots of carbohydrates and limit fat has been very bad advice.

    Much better advice would be to warn people about the dangers of over consumption of sugar and other foods that raise blood sugar levels such as bread, flour and cereals while encouraging us to eat traditional real foods such as meat, fish, eggs and butter.

    This program aired this week on Australian national TV takes a look at this issue and is well worth watching:


    I am looking forward to next week’s episode which will be looking at the issue of statins.

  5. Andrew 25 October 2013 at 6:21 pm #

    I was taken by the comment “Cholesterol is highly concentrated in the brain, where it performs several functions. It’s critical, for instance, to the function of the synapse (the ‘gap’ where one cell can communicate with another), and also has a role as an electrical insulator and as a structural ‘scaffold’ in the brain. Cholesterol is also a functional component of all cell membranes in the brain [2].” My mother suffers from Alzheimer’s and her faculties are decreasing fast. She was on cholesterol reducing drugs for several years. Is there any proven link between Alzheimers and reduced cholesterol? Seems that if the brain needs cholesterol, then tablets to reduce it might accelerate the brain’s decline? (whether they prevent heart attacks or not!) Any thoughts?

  6. mister paleo 25 October 2013 at 8:35 pm #


    You are correct. There are differing levels of “susceptibility”, a point I have made often, particularly when someone says to me, “well, my grandparents ate pasta ALL their life, neither of them was ever ill, and they both lived to their nineties”… yes, then you are indeed fortunate if you inherited that resistance to life-altering health factors, but it does NOT change the fact that on a macro level, all of us are the same. The human digestive system is what it is, and ONY DIFFERS ON A MICRO LEVEL (genetics) from individual to individual.


    The study you mention is a typical example of “crap science”… rabbits are vegetarians, not omnivores, and comparing results from them doesn’t deserve a comment… there have been many “studies” like this that are just completely irrelevant…


  7. mister paleo 25 October 2013 at 11:41 pm #


    Statins like Lipitor can cross the “blood/brain barrier”, and the result is not pretty… I have watched both my father and uncle (his brother) deteriorate both cognitively AND physiologically since being prescribed statins for “cholesterol issues”…

    And that should be ONLY in my comment above, I am tired…

  8. Tony Kerstein 27 October 2013 at 6:28 pm #

    I always felt that my rapid, almost instantaneous recover from a haemorrhagic stroke was due to the fact that I refused to take statins some time previously (they were destroying my memory amngst other things. It’s good to see this study confirming this.

  9. Christopher Palmer 31 October 2013 at 4:29 pm #

    All those ‘chronic’ diseases that arise and emerge over time go through the phase of the ‘pre-condition’, like pre diabetes for the simple reason that the pathways are consitent in that the diseases result from consistent exposure to maladaptive arrangements with the environment over time. The more maladaptive are the arrangements, and the more arrangements that can be described as ‘maladaptive’ then the faster is the trend over to time, through the ‘pre-stages’ to the condition proper, Kevin.

    The great injustice in our time is that the dogma of the day has people take up with more maladaptive arrangements, or intensify one or more of the prime ones, and thence they hasten the arrival of the ‘pre’ condition and the condition itself.

  10. Christopher Palmer 31 October 2013 at 5:06 pm #

    As regards mental faculties and mental health, Dr Briffa, someone lately recommended a book to me. I took up with the book and I am about halfway through. It is proving a real epiphany where cognition is concerned.

    First published in 2000 one may be forgiven for thinking that the content may be a bit dated, and I identified one aspect of the book (a reference to the business of meat eating in the context of paleoanthropological findings) that has been usurped by new evidence, but the book and its content, farnkly, was so far ahead of its time in the year 2000 that aspects of it contunue to sound radical and revalatory today.

    The gist of it is that our hormones, their balances, and their functions are naturally tuned (by the long process of evolution) to the natural cycles of day and night, and to some extent to the seasonal vriations in day-length. We should be active when its light, and be inactive when it’s dark, and it is only in very recent years that we humans have been able to depart from this enforced natural practice. In other words the rythmicity in light and dark cycles has adaptive bearings upon the workings and function of human physiology – well not just human, but in all of biology; ‘fleshy’ and ‘leafy’ types alike.

    So this enforced rythmicity and harmony with day length is adaptive, or remained so until only very recently, when electricty totally blitzed the last vestages of luminary rythmicity. In English, Edison said, “Let there be light”, and there was, even at times when dark would help restore and normalise natural hormanl balance. Hence God saw this unnatural light, and considered it a breach of natural laws: A distinct trend away from adaptive, and advancing towards ‘maladaptive’.

    We have a ‘clock’ and ‘calander’ deep within us, and manifesting itself in many aspects physiology and metabolism, and it it is the rythmicity of daylight and dark that keep these clocks in synchronicity with natural time.

    The departure from the natural cycles of light and dark has bearing on many hormones that often swing in a kind of cascade, one alteration in one influences an alteration in another, and so on, Metlatonin, seratonin, cortisol, insulin, ghrelin, all get knocked out of balance and remain of axis for as long as the natural cycles are clouded by the the glare of the flourescent tube. It’s rare we ever immerse ourselves in deep darkness. The sync has been removed from the city. Not only we should we curse Sir Walter Raleigh for introducing us to toxic tabacco, we must curse Thomas Edison for introducing us to late nights, shifts, and relentless light.

    T.S. Wiley and Bent Formby make a compelling case that at first seems outlandish and implausible, but which is borne out, as we grow increasingly accustomed to their thesis, by plentiful examples in nature and our observations of them. Sleep, shrotage, and a lack of darkness, upsets adaptive hormonal balance in ways that reduce our cpaicity to self regualte when and how much we eat, encourages sugar cravings, promotes weight gain, places obstacles the in the way of wilful weight loss. can lead to depression, and metal health issues.

    The book is ‘LIGHTS OUT’ (TS Wiley with Bent Formby)and I highly recommend it to you and your followers. It melds very neatly with aspects of Bill Wilsons’ CARB SYNDROME theory. Have you encountered this book, Bill?


  1. wchildblog | Study suggests that cutting back on sugar and starch may preserve mental functioning as we age - 7 November 2013

    […] By Dr John Briffa on 25 October 2013, […]

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