Sugar Is Seriously Hurting Your Brain

Sugar is all over the news these days, and the news isn’t good – especially about what it’s doing to your brain. Poor memory formation, learning disorders, depression, and Alzheimer’s have all been linked to the over-consumption of sugar.

Your brain depends on sugar to function. Brain cells require two times the energy needed by all the other cells in the body, about 10% of our total daily energy requirements. That energy is derived from glucose (blood sugar), the brain’s primary fuel. So, sugar itself is not the brain’s enemy — excess sugar is.

The Not-So-Sweet Truth About the Sugar You’re Consuming 

The US Department of Agriculture estimates that the average American consumes 156 pounds of added sugar annually.  That amounts to five grocery store shelves loaded with 30 or so one pound bags of sugar each. (Psychology Today, 2012).

The Center for Disease Control puts the amount of sugar we consume at 27.5 teaspoons of sugar per day per person.  The calorie total for that amount is approximately 440 which accounts for one-quarter of a daily 2000 calorie diet. Now, you’re probably thinking that these stats sound exaggerated and that there’s no way that you consume that much sugar in a day! While you might not be eating enough straight sugar to meet this statistic, remember that there is natural sugar found in fruits and vegetables and plenty of added sugar is included in the processed foods we eat every day.

A brain-healthy diet would contain a significant amount of naturally occurring sugar from fruits and grains, for example. So sugar itself is not a problem for the brain. The problem is that we’re chronically consuming much more added sugar in processed foods, which is most often in the form of fructose. Fructose, without the fiber from plants, is quickly absorbed causing rapid blood sugar spikes and crashes.

Sugar, Diabetes, and Alzheimer’s

It has always been believed that diabetes and Alzheimer’s were associated because of the simultaneous escalation of Alzheimer’s and Type II diabetes. In fact, Alzheimer’s is sometimes referred to as Type III diabetes.

Type II diabetics are insulin resistant. That means that they don’t utilize insulin appropriately to keep blood sugar levels stable. Therefore, higher levels of insulin and blood sugar end up circulating in the body.  Over time, this damages organs including the brain.

When researchers started looking closer at the link between Alzheimer’s and diabetes, they saw several correlations.

Insulin plays a key role in brain aging and in synaptic health. Synapses are critical for the passage of signals from one neuron to another. They are believed to be the basic structure through which memory is accomplished. Diabetics are insulin resistant which means it is difficult for insulin to pass through the blood-brain barrier.

High Sugar Equals Low BDNF Levels

The research also indicates that people with diets high in added sugar have decreased amounts of BDNF (brain-derived neurotrophic factor).  BDNF is very important because, without BDNF, our brains can’t form new memories. Other research found that people with glucose metabolism problems – pre-diabetics and diabetics – have low levels of BDNF. Those levels decrease as sugar metabolism worsens.

Consistently eating added sugar starts a cascade of events which reduces BDNF, and the resulting lower levels of that brain chemical contribute to insulin resistance which then leads to Type II diabetes and metabolic syndrome (high blood pressure, high cholesterol, coronary artery disease and possibly a whole host of health problems.

Low BDNF levels are linked to depression and dementia and may be a critical factor in Alzheimer’s.

The link Between Sugar and Depression 

One large study which tracked the diets and medical conditions of 8,000 people over 22 years, found that men who consumed 67 grams or more of sugar per day were 23% more likely to be diagnosed with depression in a five-year period than men who ate 40 grams or less. The researchers report that the effect was independent of the men’s socioeconomic status, physical activity, drinking, smoking, other eating habits, body weight or physical health. The same correlation didn’t appear for women in the study, though it’s unclear why.

This isn’t proof of a definite causal relationship, and self-reporting in surveys isn’t always the most reliable. However, a 23% difference is significant even with those drawbacks. Saying sugar causes depression isn’t a reasonable conclusion from these results, but enough dots are connected to raise legitimate concerns. The finding is noteworthy because it lines up with what previous research suggests: over-consumption of sugar triggers imbalances in certain brain chemicals, upping the chances of outcomes like depression and anxiety.

In particular, it seems excess sugar impacts dopamine–the neurotransmitter that fuels the brain’s reward system–like a potent narcotic. Since addiction and mood disorders are closely associated, it may be that sugar plays a role similar to cocaine in powering the mood roller-coaster. Sugar is increasingly linked to cellular inflammation, which science is showing as a likely culprit in the onset of depression.

The bottom line is that there’s reason for concern about excess sugar in our diets. Sugar could seriously be harming your mental and brain health. This information only adds to what we already know about sugar and physical health.

About the Author

 Patricia Faust is a gerontologist specializing in brain aging, brain health, and brain function. She has a Master’s degree in Gerontological Studies from Miami University in Oxford Ohio. Patricia is a certified brain health coach as well as having a certification in Neuroscience and Wellness. She has been a co-author of various research studies through the Scripps Gerontology Center at Miami University. Her newsletter, My Boomer Brain, has an international readership, and she is regularly published in local and social media.

Patricia is available for speaking engagements, workshops or consulting.  Her perspective on brain aging and brain function is a game changer. You can contact Patricia at:


  1. Those figures on sugar consumption are startling. You’ve convinced me. Letting go of too much sugar is an obvious way to improve our health.

    • Our food is so processed that we have no idea how much sugar we are actually eating. Drawing attention to that fact may help spur people to look at ingredients on their processed food. We just have no idea what we are actually eating.

  2. Thanks for sharing the research. I have had no idea that sugar could be linked to depression for men. I’m trying to cut down on sugar consumption myself. Less sugary drinks and desserts these days…it was challenging to cut down at first but it gets better over time.

  3. Too much sugar is just bad for our health. It’s a shame that something so good can be so bad. But you are right – it is hard to reduce eating sugar but it gets easier over time. Good for you.

  4. I’m on a constant quest to ingest less sugar, so your article confirms for me the need to continue to eat less, Patricia. It does seem to be in so many of our foods these days. Many of your statistics are compelling. My mother had Alzheimer’s, so interesting that it is referred to as Type III diabetes.

  5. I remember reading Sugar Blues way back then…it’s a tough thing to get out of lives…if you read labels…it’s everywhere. What a great reminder. Thank you.

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