A Spoonful of Sugar — Destroys Memory?

In Cognitive Health, Diet and Nutrition

Memory loss
Keeping your blood sugar under control is beneficial for far more than just waistlines and diabetes prevention, it is also important to help preserve your memory as you age. Yep, that’s right — spiked blood sugar levels actually cause your brain to age prematurely, resulting in more “senior moments” than you’d care to have.

There have been other studies indicating this in the past, but a new study led by Scott A. Small, M.D., associate professor of neurology from the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain was remarkable because it showed that the activity of an important part of the memory center of the brain (called the dentate gyrus) decreases with elevated blood glucose levels.

Dr. Small’s research looked at people with type 2 diabetes and found that they had this damage to their dentate gyrus. He then looked at factors such as a high body mass index, insulin resistance, high cholesterol, and elevated blood sugar that are seen in type 2 diabetes, and replicated them in animals to determine which ones were correlated with the brain damage. He found that rapid blood sugar increases ONLY, damaged the memory center.1

Past studies have suggested that high blood sugar may play a role in Alzheimer’s disease by contributing to the plaques in the brain, but Dr. Scott’s studies show that elevated blood sugar directly damages the memory center in the brain.

Other recent studies have found that exercise is very important for preserving the memory center in the brain. Dr. Small stated that this is most likely because exercise decreases blood sugar levels. Other researchers commenting on this have stated that they believe there could be other mechanisms at play, and I agree.

For instance, animal studies have shown that stress can also impair the dentate gyrus.2

This is a precarious situation from my perspective. Here we have a condition — stress — that in and of itself can damage your memory center in the brain. Stress is also associated with increased cravings for high carb comfort foods like sweets, partly because stress reduces serotonin production. That high carb treat is a way to increase serotonin levels. But to give into that sweets craving can further damage your memory.

So to preserve your brain and memory as you age, control your blood sugar levels and make sure you manage your body’s stress response. Exercise helps with both of these.

As you know from reading my articles in the past, I believe that a carb-controlled diet is also important for optimum control of blood sugar. Since Dr. Small’s study found that rapid spikes in blood sugar were the cause of damage to the memory center, a low glycemic index diet should be of particular benefit for your brain.

Indeed, a recent Duke University study found that a very low carb diet reversed type 2 diabetes without medication,3 the very condition that Dr. Small found is a very high risk factor for destroying your memory as you age.

However, some researchers have suggested that low carb diets may not be good for your thinking powers since glucose is the primary fuel source for the brain. A recent report out of Tufts University was one such study.4

Not to worry. In my opinion and the opinion of another low carb diet researcher, Dr. Grant D. Brinkworth, the findings of the Tufts study could be nothing more than a transient effect that occurs when the body is “readjusting to an unfamiliar diet.”5 Dr. Brinkworth’s own research on this very matter found that lower carb diets slightly lowered “cognitive processing speed, but did nothing to impair a person’s working memory. So, don’t be confused by the headlines, and don’t think that you have to keep eating higher carbs to maintain your ability to think clearly.6

Make no mistake, diet and other lifestyles factors that help you control your blood sugar, not only help prevent diabetes and heart disease, they will help preserve your memory as you age. The Duke University study mentioned above tested a very low level of carbs, and had a high participant dropout rate. I do not believe that the carbs have to be that low to get results. At LMI, our patients are usually successful at controlling blood sugar on about 25% of their calories coming from carbs. That amount still allows about 100 grams of carbs per day. We strive for about half of those carbs to come from low glycemic sources like non-starchy vegetables.

To see if your efforts at blood sugar control have been effective, you should regularly monitor your fasting blood glucose levels. Levels of 95 and below are best. You can also have your hemoglobin A1c level checked, which will tell you how your blood sugar levels have been over the past 3 months. Levels from 4-5.9% are considered normal.

If your levels are high despite a lower carb diet and exercise, I would consider using blood sugar supportive nutrients like chromium, magnesium, zinc and alpha-lipoic acid.


  1. Small S, et al. Ann of Neurology. 64(6):698-706.
  2. Proc Natl Acad Sci USA. 1998 Mar.
  3. Westman EC et al. Nutr Metab. 2008;DOI:10.1186/1743-7075-5-36.
  4. Taylor H, et al. Appetite. Feb 2009.
  5. http://www.webmd.com/diet/news/20081212/no-carb-diets-may-impair-memory.
  6. Brinkworth G, et al. AJCN. Sept 2007. 86(3):580-87.