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.))
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.