What Sugar Does to Your Brain

Sugar Brain

You open a can of soda and pour that sugary drink into your mouth. The sugar travels down your throat and into your stomach and then has a very short trip from your stomach into your blood stream. As that sugar starts to move its way through your body, it eventually makes its way to your brain. You brain is happy with this shot of sugar you just gave it, because, while it only makes up only two percent of the body weight, your brain uses one-half of all the sugar energy in the body. ((Fehm HL, Kern W, Peters A. The selfish brain: competition for energy resources. Prog Brain Res. 2006;153:129-40.))

Brain Light

But, is there such a thing as too much sugar for your brain? And that soda you just drank will cause your blood sugar to skyrocket and eventually drop; what happens to your brain then? And what about other sugar-brain questions: doesn’t sugar make you or your kids hyperactive, and doesn’t sugar change your mood?

The short answer to these all these questions is: we don’t know . Scientific studies on the effects of sugar on the brain are sparse at best and most medical professionals and organizations will say that sugar has nothing to do with mood or hyperactivity. If you are surprised by that stance, you are not alone.

Most parents have witnessed firsthand the effect of sugar on little kid’s brains. Most adults will tell you that they have experienced a sort of mental fog from eating too much sugar, not to mention the sugar high and the sugar crash. But none of these experiences mean anything to researchers who report that there are no such thing as a sugar high or that hyperactivity could be caused by too much sugar.

But just because there isn’t much research on how sugar and foods that act like sugar and how they affect mental function doesn’t mean there isn’t any. This article will piece together the bits of information out there on sugar and brain function to get a better understanding of what sugar is doing to our brains. As usual, I will be including not only sugar, but foods that act like sugar in the discussion.

Brain-Derived Neurotrophic Factor

Let’s start with a brain chemical called brain-derived neurotrophic factor (BDNF). BDNF is the key to understanding what happens when sugar hits our brain.

Brain-derived neurotrophic factor is responsible for the development of new brain tissue. If you didn’t have this chemical in your brain, your brain wouldn’t develop properly and you would die very soon after birth. The key to BDNF is to understand what it does: it helps to create new neurons (nerve tissue), and, therefore new memories.

You want as much BDNF around as possible if you want to learn, grow, and have normal brain functioning.

Research has shown that high sugar diets (along with high fat diets and lack of essential fatty acids) decrease a BDNF. ((Molteni R, Barnard RJ, Ying Z, et al. A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience. 2002;112(4):803-14.)) In fact, the relationship between BDNF and sugar gets even more interesting: low amounts of BDNF actually leads to insulin resistance, metabolic syndrome and even diabetes. ((Krabbe KS, Nielsen AR, Krogh-Madsen R, et al. Brain-derived neurotrophic factor (BDNF) and type 2 diabetes. Diabetologia. 2007 Feb;50(2):431-8. Epub 2006 Dec 7.)) This means that high sugar in the blood leads to low BDNF, and then low BDNF leads to a worsening of blood sugar control, which leads to high blood sugar, which leads to worse blood sugar control… and the cycle continues.

In an interesting study on rats, it was discovered that the animals that had the best ability to learn spatial and memory tasks also had the highest amount of BDNF. It took only two months on a high sugar and high fat diet to significantly reduce BDNF in the brains of the experimental animals and for the reduction to have an effect on the animal’s ability to perform spatial and memory tasks. ((Molteni R, Barnard RJ, Ying Z, Roberts CK, Gómez-Pinilla F. A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience. 2002;112(4):803-14.))

Low BDNF is no small thing as it has also been associated with depression, obsessive-compulsive disorder, Alzheimer’s disease and other dementias, Huntington’s disease, Rett syndrome, and schizophrenia.

But there is much more to the sugar-brain story than BDNF, let’s take a look.


Schizophrenia is one of the best places to start when discussing how sugar affects our brains. There are quite a few clinical studies that link the consumption of grains (foods that act like sugar) with schizophrenia. ((Peet M. International variations in the outcome of schizophrenia and the prevalence of depression in relation to national dietary practices: an ecological analysis. Br J Psychiatry. 2004 May;184:404-8.)) It has long been thought that people who are schizophrenic may have a problem with the protein found in many grains (gluten) and there is a strong association between schizophrenia and Celiac disease. ((Kalaydjian AE, Eaton W, Cascella N, Fasano A. The gluten connection: the association between schizophrenia and celiac disease. Acta Psychiatr Scand. 2006 Feb;113(2):82-90.))

Interestingly, there is also a close association with poor blood sugar control (metabolic syndrome) and the severity of schizophrenia:

It appears that the same dietary factors which are associated with the metabolic syndrome, including high saturated fat, high glycemic load, and low omega-3 (PUFA), may also be detrimental to the symptoms of schizophrenia. ((Peet M. Nutrition and schizophrenia: beyond omega-3 fatty acids. Prostaglandins Leukot Essent Fatty Acids. 2004 Apr;70(4):417-22.))

These researcher show that once again, a diet low in essential fatty acids (omega-3) and high in fat and sugar will decrease BDNF and it makes me wonder if sugar and foods that act like sugar may be the “smoking gun” in schizophrenia.

Depression and Anxiety

As a hint that how we live and what we eat have some effect on our moods, it has long been known that coronary heart disease and diabetes all are common in people with depression. ((Peet M. International variations in the outcome of schizophrenia and the prevalence of depression in relation to national dietary practices: an ecological analysis. Br J Psychiatry. 2004 May;184:404-8.)) This means that the same dietary conditions that create heart disease and diabetes also can lead to depression. Interesting…

Sugar consumption in population studies have been shown to have a close link with major depression. ((Westover AN, Marangell LB. A cross-national relationship between sugar consumption and major depression? Depress Anxiety. 2002;16(3):118-20))Researchers suggest that the sugar and brain association may be due to the oxidative stress that sugar can cause or the change in beta-endorphins (brain chemicals that make us feel good) that comes about because of sugar use.

Anxiety, too, has been closely linked with sugar use in a number of studies. ((Yannakoulia M, Panagiotakos DB, Pitsavos C, et al. Eating habits in relations to anxiety symptoms among apparently healthy adults. A pattern analysis from the ATTICA Study. Appetite. 2008 Nov;51(3):519-25.))


Perhaps the biggest questions arise when discussing children, mood, behavior and sugar. While any parent would tell you that sugar can dramatically change the behavior of a child, the medical community is silent. There have been a few studies that show an association between high blood sugars and problem behaviors, but these studies have mostly been performed in children who already have blood sugar problems (such as diabetes). ((Valdovinos MG, Weyand D. Blood glucose levels and problem behavior. Res Dev Disabil. 2006 Mar-Apr;27(2):227-31.)) ((McDonnell CM, Northam EA, Donath SM, et al. Hyperglycemia and externalizing behavior in children with type 1 diabetes. Diabetes Care. 2007 Sep;30(9):2211-5.)) More studies need to be done and need to be done in children with normal blood sugar.

Autism is an interesting exception to the lack of research. A review by the prestigious Cochrane review admitted that many of the studies linking foods that act like sugar (grains) and gluten to autism have been of poor quality, but they do point to one study that does show a relationship between a gluten-free diet and improvement in the symptoms of autism. ((Millward C, Ferriter M, Calver S, Connell-Jones G. Gluten- and casein-free diets for autistic spectrum disorder. Cochrane Database Syst Rev. 2004;(2):CD003498.)) While far from conclusive, these studies open the possibility of a solution for the growing epidemic of autism.

Healthy Brain Plan

Okay, let’s say you actually want to take care of your brain. What is the best way to go?

  • Avoid grains and sugars: Read my book Sugarettes or take the 30 Sugar Free Days Challenge, and get yourself off sugar and foods that act like sugar.
  • Exercise: It has been shown that exercise is great for your brain, and it increases BDNF. ((Exercise: Ang ET, Gomez-Pinilla F. Potential therapeutic effects of exercise to the brain. Curr Med Chem. 2007;14(24):2564-71. ))
  • Supplement: Your brain thrives on vitamins, especially the B vitamins and make sure you are taking some form of omega 3 oils (fish oils).

We can take care of our brains much better than we do and knowing that the foods that we put into our mouths can dramatically how we think, how we feel and act, and which diseases we get means that your brain and how well it functions is in your hands. You have a choice and what you eat and drink can make dramatic differences in how you think, feel and behave.



About the Author

I'm Dr. Scott Olson ND. I'm a Naturopathic doctor who specializes in diet, health, nutrition, and alternative medicine. I've written numerous books and articles on health, medicine, and alternative medicine I want to help you get healthy! Take a look at my blog and make sure you join in the conversation!

42 Comments on this article. Feel free to join this conversation.

  1. William January 4, 2015 at 10:55 pm - Reply

    I have schizophrenia and i can personally testify that when i was institutionalized about a year and a half ago i was consuming more sugar than i had ever in my life and on top of that i was literally living off of hamburger helper and fried rice dishes. I significantly improved within a week or two of being hospitalized and that was before they put me on the meds. I noticed the pattern in hindsight and decided to finally look into it and found this article. Thanks a lot, and I’m definitely going to change some things with my diet now. The medication helps a lot, but I still take in a lot of grains and fat and sugar, and not a lot of fruits and veggies and my memory and math skills aren’t really that good right now; something I’ve been worried about. I recall a time between the ages 18 and 19 when my grain an sugar intake was low and i could approximate fairly complex math in my head in a second or two, literally, though not perfectly for big numbers, but accurate to within a percent or so, and that all changed within a year of noticing that i could do that. Now, my math skills suck and when i read sometimes it’s like i read it but i don’t process the information. Hopefully, you just helped me solve some of that for me. Thanks again.

    • Dr. Scott January 5, 2015 at 5:51 am - Reply


      It sounds like you are on the right track! Great job figuring out the connection between the food you eat and your symptoms. If you are looking for more reading, I would check out the book Grain Brain; here is a good link for more info: http://www.drperlmutter.com/tag/schizophrenia/.

      Best of luck!

      Dr. Scott

  2. Joyce November 24, 2014 at 10:41 am - Reply

    Does sugar intake cause MS or make it worse?

    • Dr. Scott November 26, 2014 at 5:02 am - Reply


      I hadn’t been asked this question before and I took a few days to research it. No, I haven’t found a connection in the scientific literature. I am, however, sure that consuming as much sugar as we do is not good for our health in other ways. There is a doctor, Terry Wahls MD, who has a protocol that I would strongly encourage you to do that is based on whole foods. Check it out here: http://terrywahls.com/

      Hope that helps,

      Dr. Scott

  3. Monica October 11, 2014 at 11:02 am - Reply

    I’m so glad I found this article. My 17 year old was diagnosed with schizophrenia back in January. With no hope of him ever being able to do anything with his life. After doing research I came across several options and he now follows a version of the Paleo diet. I had to find something that could help since I noticed his anxiety was bad. As though his meds we’re not working. The new way of eating has helped so much it’s unbelievable. He still takes his anti-psychotic meds but he’s really sleepy. The delusions are still there but he can put them to the “side” and get by. They worsen when he eats something he can’t tolerate. (Gluten, sugar, artificial sweetener, cooked tomatoes or caffeine). His doctors don’t believe us. They think I’m delusional when I bring it up. All I can say is that this seems to be working and I hope soon someone will believe us.

    • Dr. Scott October 12, 2014 at 6:45 am - Reply


      It sounds like you are headed in the right direction. The world of diet and brain disorders is largely unexplored, but there is no doubt that some of the food we eat can have dramatic effects on how we think. People with Schizophrenia may be more sensitive than others. There are a few old research studies on the link between gluten and schizophrenia; here is a recent review that you can take to your doctor: RKalaydjian AE, Eaton W, Cascella N, Fasano A. The gluten connection: the association between schizophrenia and celiac disease. Acta Psychiatr Scand. 2006 Feb;113(2):82-90. Review. PubMed PMID: 16423158.

      Best of luck,

      Dr. Scott

  4. Arella August 23, 2014 at 11:44 am - Reply

    I was diagnosed with schizophrenia 7 years ago. Istopped eating sugar and grains and have been off my medication for nine months without any symptoms. It’s such a simple solution to years of suffering. People don’t believe it but it makes so much sense.

    • Dr. Scott August 25, 2014 at 7:55 am - Reply


      Thanks for your comments! Great to hear about the power of changes in our diets to change our lives!

      Dr. Scott

  5. julie June 12, 2014 at 5:59 am - Reply

    Is Chia equivalent to fish emega 3? Is Chia beneficial?

    • Dr. Scott June 15, 2014 at 6:53 am - Reply


      No, Chia seeds do not contain the same kind of omega-3 found in fish oil. Chia seeds are high in ALA and while on paper ALA can turn into EPA/DHA (fish oil), it rarely does so in the the body.

      Hope that helps,

      Dr. Scott

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