“Brain functions such as thinking, memory, and learning are closely linked to glucose levels and how efficiently the brain uses this fuel source…Although the brain needs glucose, too much of this energy source can be a bad thing.” – Harvard Medical School, Department of Neurobiology

Sugar is a form of glucose, which serves as a primary source of energy for every cell in the human body. As the most nerve-dense organ in our body, the brain consumes a disproportionate amount of this energy. Approximately one-half of all glucose (and sugar) derived energy is required for the brain to function properly.

“The brain is dependent on sugar as its main fuel. It cannot be without it,” states Vera Novak, MD, PhD, and associate professor of medicine at Beth Israel Deaconess Medical Center – a teaching hospital of Harvard Medical School (HMS).

In short, without glucose, our brain cannot perform even the most basic of functions.

Too little glucose (or sugar) can lead to hypoglycemia, a common condition among pre-diabetics and diabetics. Also, glucose deficiency can interrupt neuronal production and transmission, which can manifest into various cognitive disorders.

As you’ll soon see, excessive amounts of sugar in the blood can also lead to a variety of cognitive problems. It is important, therefore, to determine what makes up a deficient and excessive amount of glucose in the brain, along with repercussions of each state. In this article, we focus on the latter: excessive glucose levels and the subsequent impact on the brain.

Besides describing the effects of inordinate glucose levels, we’ll also provide some helpful information pertaining to the appropriate levels of glucose in the body and brain – and how it can be healthily attained and maintained.

Why too much sugar is a bad thing

Simply put, too much glucose as sugar speeds up cellular aging and stunts cell growth. When cellular development is thwarted, a variety of medical problems may manifest.

Here are just some of the damaging effects of excessive sugar intake on the brain:

1. Faster cellular aging

Per a 2012 study at the University of California at Los Angeles (UCLA), research results “indicated a positive relationship between the consumption of fructose, another form of sugar, and the aging of cells,” according to HMS.

2. Memory problems

High glucose levels are linked to memory and cognitive deficiencies, according to a 2009 study by a team of scientists at the University Montreal and Boston College.

3. Same effects on brain as stress

Per a study by the University of New South Wales in Austria, high sugar intake is “as damaging the brain as extreme stress or abuse.” (Abuse? Really? Didn’t see that coming.)

4. Difficulty responding to stress

In another study, consuming too much sugar “led to lower expression of (brain) receptor that binds the major stress hormone cortisol, which may affect the ability to recover from exposure to a stressful situation.”

5. Shrinks hippocampus

Research shows that excessive sugar levels may shrink the hippocampus. Located within the brain’s medial temporal lobe, the hippocampus “forms an important part of the limbic system, the region that regulates emotions…(it) is associated mainly with memory, in particular long-term memory. The organ also plays an important role in spatial navigation.”

6. Increases risk for diabetes

Studies show that, although high levels of sugar aren’t solely responsible for developing type 2 diabetes, it increases the risk of the disease. Type 2 diabetes is a medical condition in which cells “become overwhelmed by insulin and fails to properly respond; they become resistant to insulin.”

Insulin is a hormone required to normalize blood sugar levels. When the body lacks this hormone, glucose levels spike within the brain and body. Per HMS, “High glucose levels can affect the brain’s functional connectivity, which links brain regions that share functional properties, and brain matter.” Brain atrophy and small-vessel disease – a condition which narrows blood pathways to the brain – can lead to several cognitive problems. One such problem is vascular dementia – a condition very similar to Alzheimer’s Disease .

Sugar and Kids

The damaging effects of sugar is extremely disturbing when one considers the largest consumers of sugar: children.

Per the USDA Economic Research Service, the average child under 12 years consumes 49 pounds of sugar per year. Adults? 46 pounds. This means that our most vulnerable demographic consumes more sugar than a full-grown man or woman – and with an undeveloped body.

Dr. Jennifer Shu, a board-certified pediatrician states: “Eating too much (sugar) can make kids gain weight, which then puts them at a greater risk for diabetes, high blood pressure, and high cholesterol – three major contributors to heart disease.”

In other words, parents should taper their child’s “sweet tooth.”

The above list is not exhaustive. It’s quite astonishing that medical experts have been warning about sugar’s negative effects on the waistline for years; yet these same experts had little to nothing to say about its effects on the brain.

The all-important question is “how much sugar should I be eating?”

According to the American Heart Association (AHA), recommended sugar intake is:

For men: 38 grams (9 teaspoons)

Women: 25 grams (6 teaspoons)

Children (ages 2 to 18): 25 grams (6 teaspoons)

Children (under 2 years): Zero added sugars

Harvard Medical School. (2017). Sugar and the Brain. Retrieved from http://neuro.hms.harvard.edu/harvard-mahoney-neuroscience-institute/brain-newsletter/and-brain-series/sugar-and-brain

Mandal, A., M.D. (2014, January 14). Hippocampus Functions. Retrieved from http://www.news-medical.net/health/Hippocampus-Functions.aspx
Maniam, J., Morris, M. (2016, February 17). High-sugar diet is as ‘damaging to your brain as extreme stress or ABUSE.’ Mail Online. Retrieved from http://www.dailymail.co.uk/health/article-3450298/High-sugar-diet-damaging-brain-extreme-stress-ABUSE.html
Mercola, J., D.O. (2016, September 7). How High-Sugar Diets Speed You Toward an Early Grave. Retrieved from http://articles.mercola.com/sites/articles/archive/2016/09/07/recommended-sugar-intake.aspx#_edn7
Remnarace, C. Sugar Shock (n.d.) Parents Magazine. Retrieved from http://www.parents.com/recipes/nutrition/kids/sugar-shock/