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How Carbohydrates Affect The Brain

How Carbs Affect The Brain

As diabetics we spend a lot of time counting carbs and measuring our blood glucose levels. We also experience our fair share of blood sugar swings. We are all aware of the exhausted feeling we get with hyperglycemic and the brain fog of hypoglycemia. In this article we will take a look at how exactly blood glucose and carbohydrate affects the brain and how we can better manage this as diabetics.

Where does the brain get its energy from?

Glucose is a form of sugar that fuels the cells in your body. It is transported in the bloodstream and normally absorbed through the cell walls in response to the presence of the hormone insulin.

The main source of blood glucose is from eating carbohydrates …

Glucose is the primary energy source for brain cells. Because neurons can’t store glucose internally they rely on a constant supply from the bloodstream. The main source of blood glucose is from eating carbohydrates as part of our diet. Carbohydrates include starches and sugars in fruits vegetables, rice and grains.

What exactly are carbohydrates?

Carbohydrates area family of nutrients that are made of chains of sugar molecules. They are usually categorised into two groups: Complex Carbohydrates and Simple Carbohydrates.

Complex carbohydrates tend to be considered healthier and are commonly found in natural food sources. 

What are Complex Carbohydrates?

They are made of long chains of sugar molecules that are slower to break down into the shorter chain glucose molecules that the brain uses as a source of energy.

In addition the natural sources of complex carbohydrates are typically made of cells with cellulose fiber walls that are slow to digest in the stomach. These two factors combined mean that complex carbohydrates tend to result in a slower release of glucose into the bloodstream than simpler carbohydrates.

Good Carbs vs. Bad Carbs

From Visually.

What are Simple Carbohydrates?

Simple carbohydrates on the other hand tend to be considered unhealthy and are commonly found in more refined processed foods as well as sweeter natural foods.

These carbohydrates are made of shorter chains of sugar molecules and are easier to break down into glucose molecules to enter the bloodstream. Some foods that are particularly rich in simple carbohydrates such as fruit juice, corn syrup or honey are so easily broken down and absorbed that their effect on blood glucose is similar to an injection directly into the vein.

Brain Electric Signals Visual Representation
Brain Electric Signals Visual Representation

How much energy does the brain need?

Each brain cell requires double the energy of a typical cell in your body. Neurons are in a near constant state of activity. Even when they are not actively firing they are repairing and healing themselves. They manufacture neurotransmitters and enzymes which then need to be transported to the ends of nerve branches that can reach up to several feet in length.

Why do Neurons take up that much energy?

By far the most energy is consumed by the bioelectrical signals neurons produce to communicate throughout the nervous system. In fact these nerve transmissions alone account for half of the brain’s total energy requirement and nearly 10% of the energy requirement of the whole body.

All this activity combined means that the brain requires a large and constant supply of energy 24 hours a day.

How much energy does thinking and remembering use?

We all have experienced the energy drain that can result from deep thought or learning. With the amount of energy the brain consumes it’s not surprising the available glucose in the bloodstream can be quickly used up when your brain is working hard.

…deep concentration actually drains glucose

Research has shown that deep concentration actually drains glucose for the specific part of the brain that deals with learning and memory. A study from Paul E. Gold found that rats who were thinking and learning their way through a new maze experienced a reduction in the amount of glucose in their hippocampus (the area of the brain responsible for learning and memory). It was previously assumed that the body was able to provide the brain with all the glucose it needed unless it was in a state of starvation. 

Here is a short video on how blood glucose can affect the brain

Is age a factor?

In fact the research indicated that after periods of mental effort the body was not able to supply the parts of the brain responsible for memory and learning with enough energy. For younger rats the mental effort had to be fairly difficult before they started to experience a reduction in glucose levels but for older rats the glucose levels dropped by large amount even on the simpler exercises. This may help explain the more significant mental drain we experience as we age.

Is diet a factor?

Following on from this, it may not be surprising that further research has shown that giving older adults carbohydrate rich foods before a memory exercise increased their performance. Two studies from Dr.Carol Greenwood showed that giving carbohydrates to elderly people improved their memories by up to 25%.

The results of these studies may not be a unique benefit of carbohydrates themselves. Other studies have shown that regardless of the energy source, increasing the calories eaten after a night without food results in a short increase in memory function. However carbohydrates seemed to cause a longer lasting increase than fats or proteins.

Is it possible to have too much carbohydrates?

We often grab a sugary snack or drink to give us a pick me up when our energy levels are running low. While it’s true these simple carb rich snacks give you a boost, its not without its drawbacks. When you eat high carb foods your pancreas releases the hormone insulin into the bloodstream. Insulin triggers the intake of glucose from the blood into cells as well as the storage of excess glucose for later use.

Since these simple carbs give a sudden, extreme and short lived spike in glucose levels, we get a short burst of energy followed by a sudden drop off.

Stacked Hamburger
Stacked Hamburger

Effects of too much Carbohydrates

When this drop off occurs your hard working neurons may suddenly shift from a state of sufficient energy supplies to an energy crisis. This leads to the fuzzy, adrenaline filled haze that is hypoglycemia (low blood sugar). When this occurs your concentration and thinking ability is massively impaired. When hypoglycemia is particularly extreme it can even lead to unconsciousness.

…regular episodes of high blood glucose levels can start to reduce your body’s ability to respond to insulin

Over the long term regular episodes of high blood glucose levels can start to reduce your body’s ability to respond to insulin. This condition is called insulin resistance and is a primary factor in the onset of Type 2 Diabetes.

This inability to respond to insulin means that the brain cells are not able to easily absorb glucose from the blood even when it is available. It also causes narrowing of the arteries over time. These factors make the brain more susceptible to gradual damage over the long term.

The effect of soda drinks on the brain

A normal blood glucose reading for a healthy adult would be somewhere in the range of 80 to 100 mg/dL. That’s about 0.8 – 1g of sugar per litre of blood. In everyday terms that’s something like one teaspoon of sugar circulating in your bloodstream at any one time.

A regular soft drink will contain about ten times that amount of sugar and is usually finished within a few minutes. Since the drink consists of a large quantity of refined dissolved sugar it is broken down into glucose and absorbed into the bloodstream extremely quickly. In fact glucose will have already started entering the bloodstream in the mouth before you take your first gulp.

How does it affect your body?

Your body will quickly respond by producing insulin, which instructs the cells in your body to start up taking the glucose from the blood for current and future use. If the body is forced to release large amounts of insulin at once it may not be capable of cleaning up the remaining insulin in the bloodstream after the glucose spike has been reduced.

…carbonated drinks are connected with increased dehydration which deprives the brain of the fluids it needs to function normally

The excess of insulin will cause too much glucose to be removed from the blood resulting in brain cells being deprived of their main source of energy.

In addition to this, carbonated drinks are connected with increased dehydration which deprives the brain of the fluids it needs to function normally.

A Glass of Soda on a Table
A Glass of Soda on a Table

Leading source of sugar

Researchers at the Children’s Hospital in Boston have stated that “soft drinks constitute the leading source of added sugar in the diet, amounting to 36.2 grams daily for adolescent girls and 57.7 grams for boys”.

These large quantities of soda can also lead to vitamin and mineral deficiencies, especially in young children and adolescents. A study of more than 4,000 children between the ages of 2 and 17 showed that there was a 41% rise increase in soda consumed.

How soda affects vitamin intake

Furthermore high intake of soda resulted in a lower likelihood of getting the recommended levels of vitamin A, calcium and magnesium.

There are two causes for this. First the presence of sugar depletes magnesium. Second phosphoric acid present in the gut from drinking soft drinks combines with calcium and magnesium resulting in a deficiency in vital mineral absorption.

As well as its direct effects on the brain, soda has also been linked to the massive increase in childhood obesity in recent years. 

Still on the rise

The U.S. Department of Agriculture has stated that consumption of soft drinks has risen by 500% over the last 50 years. In the same timeframe childhood obesity has risen 54% for 6-11 year olds and 40% for adolescents.

On average soft drinks contribute 10.3% of the calories overweight teenage boys consume

This increase in childhood obesity has serious knock on effects for the likelihood of heart disease, strokes and diabetes in later life. On average soft drinks contribute 10.3% of the calories overweight teenage boys consume and 7.6% of the calories of others. In an effort to control the rise in obesity the National Institute of Health has recommended that people attempting to lose weight should replace their soda drinks with water.

What effect does diabetes have on the brain?

Diabetics are more likely to have reduced mental abilities as they age. This is partly due to the narrowing of the arteries which can result in micro strokes and gradual brain damage.

Type 2 diabetics are 9% more likely to develop dementia or altzheimers. People with diabetes are also more at risk of developing depression, though it is unclear whether this is due to the physical or emotional effects of the condition.

Effects on brain function

A four-year study by Harvard Medical School found that women without diabetes were twice as likely to score better than diabetic women in the same age group. In addition, the length

of time the women had been diabetic increased the likelihood that they would score worse results. The conclusion was that the effect of having diabetes on their test results was equivalent to aging an additional 4 years

Brain Function
Brain Function

Effects on cognitive abilities

In a different study across 10,000 people from different locations and ethnicities, the results of the tests were compared across a six year gap. Diabetics between the ages of 40 and 70 were shown to have a greater cognitive decline than their non diabetic equivalents. This was the case even though when surveyed the diabetic had not reported noticing any reduction in their mental abilities over the 6 years.


The results indicated that adjustments to an individuals health in their middle age can help them maintain their cognitive abilities later in later years. 

Contributing Factors

One secondary factor of continued high blood glucose levels is high blood pressure (hypertension) resulting from damage to the artery walls (atherosclerosis) and blood vessels. Studies have shows that continued high glucose from poorly managed diabetes and hypertension doubles the likelihood of experiencing reduced cognitive function later in life.

In addition to reduced cognitive function the effects of atherosclerosis lead to increased likelihood of strokes and heart attacks. 

Benefits of Regulating Blood Glucose Levels.

Over a 12 year study of type 1 diabetics it was found that good control of blood glucose levels does have a significant positive effect on reducing the risk of atherosclerosis. 

David M.Natha (Co-chairman of the Harvard Medical School study) said “Heart attacks and strokes are the major killers of people with diabetes. After following patients with type 1 diabetes for more than 12 years, we can conclude that patients who control their blood glucose significantly lower their risk for worsening atherosclerosis,”

Here is a brief video about how high glucose levels could lead to heart attack and stroke

What effects do blood sugar swings have on the brain?

The blood glucose spikes from sugars have an exaggerated affect on our brain cells because neurons are not able to store glucose like other cells in the body can. This means they feel the dropoff of blood glucose immediately with no way to counteract it. This leads to the common experience of feeling you need another sugar boost an hour or two after your snack. The result of this is a yoyoing effect on blood glucose levels.

Changes in insulin levels

Frequent blood sugar swings can cause an increase in chronic emotional stress which contributes to increased insulin levels. This increase in insulin levels can lead to faster drop offs of glucose levels as well as increased insulin resistance resulting in a vicious cycle.

One of the best ways of minimising blood sugar swings is by eating carbohydrate sources that result in a slow release of insulin into the blood. 

Measuring changes on blood glucose levels

A useful measurement of how fast a food is converted into glucose in the blood is The Glycaemic Index. Though it’s not a perfect measurement the Glycaemic Index of a food should give you a good indication of how quickly your blood sugar will rise after eating and so how much of a spike it will cause. Eating foods with a lower Glycemic Index value will result in slower release of glucose into the blood and minimise blood sugar swings. This will help you maintain your mental focus and energy levels without needing to refuel on sugary snacks.