Blood Glucose and the Brain: Sugar and Short-Term Memory

Neuroscience and Neurology CategoryMillions of older adults suffer from significant memory loss, despite the lack of a diagnosis of dementia-causing disease. This memory loss can lead to a significant decline in quality of life and often remains undiagnosed and untreated. Recently, however, scientists have begun to study the role of glucose regulation in cognitive enhancement of adults. Cognitive function and short-term memory retrieval in middle-aged and older adults may now be linked to blood sugar levels.

The brain’s primary source of fuel is glucose, unlike other organs that have multiple fuel sources. Research has long shown that ingesting drinks or foods with high glucose content before high-demand short-term memory tasks improves cognitive performance. However, people with better blood-sugar regulation performed better on the tests than those with poor glucose regulation. In other words, the faster people metabolized blood sugar, the better their memory functioned.

Low glucose checkModerate increases in blood glucose are effective in enhancing short-term memory performance and cognitive functioning across an array of domains, but while a little glucose is good, too much can be bad. Sustained elevations in blood sugar levels, as seen in conditions including impaired glucose tolerance and diabetes, lead to a decline in cognitive functioning. Simply, the longer that the glucose remains in the blood, the less fuel the brain has to function and retain memories.

These findings are owed, at least in part, to the fact that glucose affects the hippocampus — the part of the brain responsible for short-term memory. In one small study, people with high blood sugar levels actually had a smaller hippocampus than those with normal glucose regulation. Any type of insult or injury to the brain, including high blood sugar, easily damages the hippocampus. Fortunately, it is also a resilient part of the brain and its function can be recovered when blood sugar levels are controlled.

Recently, elevated blood sugar levels were found to be significant predictors of poor cognitive performance or mild cognitive impairment among middle-aged and elderly subjects. Adults with higher fasting blood sugar levels performed worse on memory function tests, whether they received glucose or a placebo prior to the test. These findings are also linked to lifestyle factors. Study participants that had poor glucose regulation, leading to high blood sugar levels, had more risk factors for poor overall health, diet, and lifestyle. People with known risk factors for diabetes or impaired glucose tolerance are at risk for elevated blood sugar levels, in addition to any person who is overweight or has a sedentary lifestyle.

The research requires more investigation before glucose-regulation becomes a mainstay of memory loss treatments, but it provides more incentive for adults to maintain healthy blood sugar levels. Not only does a healthy, active lifestyle prevent heart disease, diabetes, joint ailments, and a plethora of other conditions, but it also improves memory and cognitive functioning.


Roozendaal, B. (2003). The hippocampus mediates glucocorticoid-induced impairment of spatial memory retrieval: Dependence on the basolateral amygdala. Proceedings of the National Academy of Sciences, 100(3), 1328-1333. DOI: 10.1073/pnas.0337480100

Meikle, A., Riby, L.M., Stollery, B. (2004). The impact of glucose ingestion and gluco-regulatory control on cognitive performance: a comparison of younger and middle aged adults. Human Psychopharmacology: Clinical and Experimental, 19(8), 523-535. DOI: 10.1002/hup.643

Riby, L.M., McLaughlin, J., Riby, D.M. (2008). Lifestyle, glucose regulation and the cognitive effects of glucose load in middle-aged adults. British Journal of Nutrition DOI: 10.1017/S0007114508971324

Riby, L.M., Marriott, A., Bullock, R., Hancock, J., Smallwood, J., McLaughlin, J. (2008). The effects of glucose ingestion and glucose regulation on memory performance in older adults with mild cognitive impairment. European Journal of Clinical Nutrition DOI: 10.1038/sj.ejcn.1602981

  • Thank you.
    I’ve always been somewhat skeptical of the simplified advice to eat sugar for improved cognitive performance. There’s always more to the story.

  • Julie

    I read about the effects of glucose & many more things that people should pay attention to in their diet to help their memory and general well being. The book is called “7 Steps to a Healthy Brain” by Dr. Paul Winner.

  • Great article.

    I continue to be impressed with the huge impact of life’s little steps. Eating right, maintaining a healthy weight level, exercising on a consistent basis – these are truly the hallmarks of healthy living.

    I appreciate your highlighting the issue of blood sugar levels among the elderly. As you know, many studies support the benefits of active exercise for this group. Personally, I always favor a non-medical intervention when possible – things like natural foods, fresh air, maybe a walk through the park…

    Thanks again for the article,


  • This is a very interesting and well written article about short term memory loss – thank you for that.

    There are many reasons for an apparent decline in memory performance and certainly what we ingest will have an impact. This appears to be a well researched article and brings the issue of the effect of blood sugar levels to a level that we lay people can understand.

    I suppose the only challenge with this knowledge is how do we know what our blood sugar levels are and whether they are too high or too low? And what of our glucose regulation performance – is mine at the optimum level? If it isn’t how will I know?

    If there are tests to give us this information then perhaps we can modify our eating habits to adjust the blood sugar level accordingly in light of that knowledge.

    Perhaps the ordinary person isn’t going to go to these lengths to improve their short term memory and so it is here that commonsense should prevail.

    Clearly what we eat will affect all aspects of our bodily functions, not least the cognative ones. So a good healthy balanced diet – plenty of fresh stuff, lots of green stuff, good hydration and the right mix of carbohydrates and proteins should be a great place to start.

    Seeking nutritional advice is always a good idea too but plenty of greens and fresh “alive looking” food will get you going until the professionals can guide you properly.

    If you do begin to have short term memory problems then maybe then is the time to get the blood sugar levels tested.

    However before you do, make sure that you have fully explored the other possible causes too.

    As someone who helps people understand how to use their memory more effectively through a variety of techniques (mnemonic devices and the like), there are other reasons why the short term memory may appear to fail us but actually are caused by other factors which are well within our control.

    If you have ever put your keys down at home and then are unable to find them again (even if you are the only one at home!) then have a read of my article “Short Term Memory Loss – What Causes It” on my Memory Improvement Blog

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  • jays

    Thank you for this article. All the puzzle pieces fit together now. =)

Jennifer Gibson, PharmD

Jennifer Gibson, PharmD, is a practicing clinical pharmacist and medical writer/editor with experience in researching and preparing scientific publications, developing public relations materials, creating educational resources and presentations, and editing technical manuscripts. She is the owner of Excalibur Scientific, LLC.

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