The Human Brain – Carbohydrates – Franklin Institute

Nourish – Carbohydrates Fuel Your Brain
Brain Energy Demand

Your brain cells need two times more energy than the other cells in your body.

Neurons, the cells that communicate with each other, have a high demand for energy because they’re always in a state of metabolic activity. Even during sleep, neurons are still at work repairing and rebuilding their worn out structural components.

They are manufacturing enzymes and neurotransmitters that must be transported out to the very ends of their– nerve branches, some that can be several inches, or feet, away.

Most demanding of a neuron’s energy, however, are the bioelectric signals responsible for communication throughout the nervous system. This nerve transmission consumes one-half of all the brain’s energy (nearly 10% of the whole body’s energy).


Neurons from entorhinal cortex (Limbic System)

©1998 Dr. Norberto Cysne Coimbra M.Sc., Ph.D., Laboratory of Neuroanatomy and Neuropsychobiology, Faculty of Medicine of Ribeirão Preto of the University of são Paulo; Neuroscience Art Galleries


Brain Power – The Energy of Thought and Memory

Most of us have discovered that thinking can be tiring, even exhausting. As the primary source of energy in the human brain, glucose can be rapidly used up during mental activity.

Some interesting research has shown that mental concentration actually drains glucose from a key part of the brain associated with memory and learning – underscoring just how crucial this blood sugar is for proper brain function.


Glucose, Learning and Memory – Study    

Psychology professor Paul E. Gold has researched the stability of glucose levels in the brain. Working with Ewan C. McNay , they found that as rats went through a maze, concentrations of glucose declined in the animals’ hippocampus , a key brain area involved in learning and memory – even more dramatically so in older brains.

Except under conditions of starvation, it was thought that the brain always had an ample supply of glucose. “While this is the case in terms of consciousness, the new findings suggest that glucose is not always present in ample amounts to optimally support learning and memory functions,” said Gold, who is director of the Medical Scholars Program in the University of Illinois College of Medicine.


“The brain runs on glucose. Young rats can do a pretty good job of supplying all the glucose that a particular area of the brain needs until the task becomes difficult,” explained McNay, a postdoctoral researcher in psychology at Yale University. “For an old rat given the same task, the brain glucose supply vanishes out the window. This correlates with a big deficit in performance. A lack of fuel affects the ability to think and remember.”


Glucose, Age, Memory and Learning – Study

In the May 2001 issue of Neurobiology of Learning and Memory, Gold, and McNay reported that glucose drainage during a task is specific to the hippocampus, where extracellular levels fell by 30%. (Other brain areas remained stable.) “Only the part of the brain involved with what the animal is asked to do is affected by changes in glucose usage,” Gold said.-Not sure how study relates to other study about age, memory and learning.

In the May 2001 issue of the Journal of Gerontology, Gold and McNay described a study which showed how 24-month-old rats experienced a 48% decline in hippocampal extracellular glucose levels, and needed 30 minutes to recover from a maze-related task. Younger, three-month-old rats had only a 12% decline and recovered quickly. When older rats were injected with glucose supplements prior to testing, they did not show the drainage of glucose – and performed at the same levels as the younger rats.


“Glucose enhances learning and memory not only in rats but also in many populations of humans,” says Gold. “For schoolchildren, this research implies that the contents and timing of meals may need to be coordinated to have the most beneficial cognitive effects that enhance learning.”


How Carbohydrate Foods Can Improve Memory in Older Adults – Studies

When Dr. Carol Greenwood tested the memory of older adults after they ate a breakfast of mashed potatoes or barley, she found that “eating carbohydrate foods can improve memory within an hour after ingestion in healthy elderly people with relatively poor memories.”

In another study, Greenwood and her colleagues at the University of Toronto gave a group of healthy senior citizens a bowl of cereal and milk, along with white grape juice for breakfast. Another group only drank water. When tested twenty minutes later, the cereal-eaters had a better memory – able to remember 25% more facts.


Not only does a diet lacking in carbohydrates cut off the brain’s main energy supply, Greenwood said a scarcity of glucose can impede the synthesis of acetylcholine, one of the brain’s key neurotransmitters.1


Breakfast and Memory – Studies

Regardless of the source, caloric intake after an overnight fast can cause a short burst in memory capacity, scientists discovered. Carbohydrates, however, generally brought longer-term memory benefits than either fats or proteins in the people tested.

Lead scientist, Dr. Carol Greenwood, emphasized the advantage of nutritious carbohydrates – fruits, vegetables, and whole grains – instead of simple sugars such as pastries. Her studies point to the importance of children’s breakfasts to school performance. 2

Another University of Toronto study compared the memory-improving effects of different breakfasts eaten after an overnight fast. Participants who consumed a carbohydrate breakfast of potatoes or barley performed better on short- and long-term memory tests, compared to those who consumed only a glucose-laden lemon drink. Both groups did better than the participants who consumed only an inactive placebo.


“Our study showed that eating carbohydrate foods can improve memory within an hour after ingestion in healthy elderly people with relatively poor memories,” said lead author Randall J. Kaplan. “Individuals with seemingly minor deficits in glucose regulation appear to perform worse on cognitive (memory) tests and are most sensitive to the beneficial effects of carbohydrates.”3


Too Much Blood Sugar – Too Little Brain Sugar

A sugary snack or soft drink that quickly raises your blood sugar level gives you a boost (and any caffeine adds to the lift), but it’s short-lived. When you eat something with a high sugar content your pancreas starts to secrete insulin. Insulin triggers cells throughout your body to pull the excess glucose out of your bloodstream and store it for later use.

Soon, the glucose available to your brain has dropped. Neurons, unable to store glucose, experience an energy crisis. Hours later, you feel spaced-out, weak, confused, and/or nervous. Your ability to focus and think suffers. The name for this glucose deficiency is hypoglycemia , and it can even lead to unconsciousness.


High Sugar Intake Over Time

Repeatedly overloading the bloodstream with sugar can diminish the body’s ability to respond to insulin, and type 2 diabetes may develop.


This is not good for the brain, because diabetes causes a narrowing of the arteries and makes the brain more susceptible to gradual damage. People with diabetes are more vulnerable to depression and are more likely to suffer a decline in mental ability as they age.


Low Blood Sugar Slows Brain – Study

Low blood glucose levels can lead to a significant deterioration in attention abilities, University of Edinburgh researchers concluded after testing healthy individuals in whom hypoglycemia had been induced.


Auditory and visual information was processed more slowly when the subjects’ brains were temporarily deprived of its main source of energy. 4


Soft Drinks are Hard on Your Brain

When levels of circulating glucose drop, the initial sugar-high turns into an energy crisis for your brain. (Neurons cannot store glucose, like body cells can.) An hour or two after drinking a sugary soft drink, you feel the need for another boost.


What Happens in Your Body When You Have a Soft Drink

If you’ve ever had a blood test that measured your fasting blood glucose level, it should be somewhere around 100 milligrams per deciliter. That’s one gram of blood sugar per liter of blood, which translates into only about five grams (a teaspoon) of sugar in circulation throughout your entire bloodstream.

Let’s say you suck down the typical non-diet soft drink that contains ten times that amount of sugar, which is then quickly absorbed and enters into your bloodstream. Sensors in your brain’s hypothalamus will instruct your pancreas to secrete insulin, which causes the cells in your body to pull this overload of glucose out of your bloodstream and store it for later use.

Even when blood sugar levels are again normalized, insulin levels can remain high, because your liver may be unable to remove the circulating insulin fast enough.


In addition, drinking carbonated soft drinks decreases the amount of pure water a person consumes, which can lead to dehydration that depletes the brain and other organs of fluids. (The brain contains a high percentage of water.)

“Currently, soft drinks constitute the leading source of added sugars in the diet, amounting to 36.2 grams daily for adolescent girls and 57.7 grams for boys,” according to researchers at the Children’s Hospital in Boston. 5


Soda and Vitamin Deficiencies – Study

What’s more, drinking large quantities of soda can lead to deficiencies in several important vitamins and minerals. A survey of more than 4,000 children, aged 2 to 17 years, found that soda consumption rose 41% between 1989-1995. Soda drinkers were less likely to get the recommended levels of vitamin A or calcium, and were at increased risk of magnesium deficiency. 6


Sugar depletes magnesium, and the high levels of phosphoric acid in soft drinks can combine with calcium and magnesium in the gut to cause a loss of these vital minerals.


Liquid Candy-Soda Statistics

In 1998, the Center for Science in the Public Interest (CSPI) published a report titled ” Liquid Candy : How Soft Drinks are Harming Americans’ Health.” A Washington-based nonprofit education and advocacy organization, CSPI focuses on improving the safety and nutritional quality of our food supply. Michael F. Jacobson, Ph.D., writes:

“Teenage girls consume only 60% of the recommended amount of calcium, with soda-pop drinkers consuming almost one-fifth less calcium than non-drinkers. It is crucial for females in their teens and twenties to build up bone mass to reduce the risk of osteoporosis later in life….

“Obesity rates have risen in tandem with soda consumption. Soft drinks provide 10.3% of the calories consumed by overweight teenage boys, but only 7.6% of the calories consumed by other boys. The National Institutes of Health recommends that people trying to lose or control their weight should drink water instead of soft drinks with sugar.”


The U.S. Department of Agriculture says that consumption of soft drinks has increased 500% in the last 50 years. During this time, childhood obesity in the U.S. jumped 54% for 6-11 year-olds, and 40% for adolescents.

This boom in childhood obesity could lead in adulthood to a sharp rise in strokes, heart disease, and other vascular-related illnesses. In an ultrasound study of 48 severely obese children, French researchers at the Necker Enfants-Malades Teaching Hospital observed a general decline in function of the lining of the children’s arteries, including a loss of vascular elasticity. 7


Sugar, Diabetes and The Brain

Diabetics are more likely to suffer a decline in mental ability as they age, due to a narrowing of the arteries that can lead to tiny strokes and gradual brain damage.

Diabetics experience a decline in speed of processing information.

People with type 2 diabetes have a 9% increased risk of developing dementia – and Alzheimer’s disease. People with diabetes are also more susceptible to depression than the general population.


How Diabetes Can Develop

When for years you repeatedly overload your bloodstream with simple sugars, refined carbohydrates, soft drinks, etc., the swings in blood sugar can take their toll on your body’s ability to respond to insulin. Receptors for this hormone may eventually malfunction, becoming “insulin-resistant,” so that blood sugar levels remain high – even as your pancreas continues to secrete insulin. Type 2 diabetes can develop.


Nearly 6% of the American population has diabetes. For African Americans, it is 10%. For Native Americans, diabetes increased by 29% between 1990 and 1997 – more than twice the rate for the general U.S. population.

An estimated five million more people have diabetes but don’t know it, and nearly 800,000 new cases are diagnosed each year.


Children and Diabetes – Studies

Type 2 diabetes used to be called “adult-onset” diabetes, because it mostly occurred in people over 50. But no longer.

The rising rate of diabetes in children is epidemic. “If you go back 20 years, about 2% of all cases of new onset diabetes (type 2) were in people between 9 and 19 years old. Now, it’s about 30% to 50%,” says Dr. Gerald Bernstein, an endocrinologist with New York’s Beth Israel Medical Center.

Among Americans in their thirties, the 1990s saw a 70% rise in type 2 diabetes, reports the CDC. Other age groups also showed significant increases. For those in their forties the disease rose by 40%, and by 31% for those in their fifties.


A Mayo Clinic study of 11,000 people found that diabetics had a greater decline in cognitive processing speed. “People with either diabetes or strokes are at higher risk not only for cognitive decline but dementia,” said Mary Haan, a researcher at University of Michigan School of Public Health. 8

In a study of 6,370 patients, ages 55 and older, Dutch researchers at the Erasmus University Medical School found that those with type 2 diabetes faced nearly a 9% increased risk of developing dementia – and Alzheimer’s disease in some cases. 9


How Diabetes May Be Linked to Mental Decline – Studies

Over a four-year period, Harvard Medical School researchers tested the memory and mental function of 2,300 women, 70 to 78 years old. Women without diabetes were more than twice as likely to score better than those with diabetes. Also, the longer a woman had diabetes, the more likely she would score poorly on the tests. “Based on calculations within the women in our study, we found that having diabetes was equivalent to aging 4 years in terms of scores,” Dr. Francine Grodstein and her colleagues concluded. 10

In a multiethnic, multicenter study of vascular disease in more than 10,000 people, cognitive test scores were compared six years apart. Diabetes was associated with greater cognitive decline in participants aged 40 to 70 years old, (while high blood pressure was associated with greater cognitive decline only in those older than 58).


“While the participants in the study may not have noticed any decline in their mental ability, the decline was statistically significant,” says David Knopman, M.D., a Mayo Clinic neurologist and the senior author of the study. “The results point to the fact that there are things some people may be able to do during middle age to help preserve our mental abilities later in life.” 11


How Hypertension and Diabetes May Double the Risk of Mental Decline – Study

Studies indicate that the presence of both uncontrolled diabetes and hypertension doubles the risk of decreased mental functioning later in life. (Each condition is independently associated with accelerated age-related declines in cognitive functioning.)


“We are talking about hypertension and diabetes as insidious predictors of gradual and subtle decline in cognitive ability,” said Merrill Elias, a founding investigator of the Maine-Syracuse Study of Hypertension and Cognitive Function. “Effective treatment or prevention practices can delay or prevent accelerated cognitive decline associated with cardiovascular risk factors.” 12


High Glucose and Stroke – Study

Research presented in June 2001 at the American Diabetes Association’s annual meeting showed that high blood glucose levels play a role in the development of atherosclerosis (hardening of the arteries), putting people with diabetes at increased risk for heart disease and stroke.


“Heart attacks and stroke 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,” said David M. Nathan, M.D., co-chairman of the NIH-sponsored study and an investigator at Harvard Medical School.


Exercise and Diet are Effective Against Diabetes – Study

When people at high risk for type 2 diabetes exercised at least 30 minutes a day, they reduced their risk by 58%, even without medication. In fact, exercise and diet proved to be nearly twice as effective as a popular diabetes drug.

These were among the findings from the Diabetes Prevention Program announced by the National Institutes of Health in August 2001. This major clinical trial compared diet and exercise to drug treatment in 3,234 people with impaired glucose tolerance, a condition in which blood glucose levels are higher than normal (but not yet diabetic).


Participants maintained their physical activity at 30 minutes per day, usually with walking or other moderate intensity exercise. They also ate a low-fat diet.


Check the Glycemic Index

Foods with a low glycemic index number gradually release glucose into your bloodstream. This gradual release helps minimize blood sugar swings and optimizes brainpower and mental focus


apple 38
apricot, canned 64
apricot, dried 30
banana 62
banana, unripe 30
cantaloupe 65
cherries 22
dates, dried 103
fruit cocktail 55
grapefruit 25
grapes 43
kiwi 52
mango 55
orange 43
papaya 58
peach 42
pear 36
pineapple 66
plum 24
raisins 64
strawberries 32
watermelon 72

beets 64
carrots, cooked 39
carrot juice 45
French fries 75
parsnips 97
peas, dried 22
peas, green 48
potato, boiled 56
potato mashed 73
potato, microwaved 82
potato, instant 83
potato, baked 85
pumpkin 75
rutabaga 72
sweet corn 55
sweet potato 54
yam 51

apple 41
grapefruit 48
orange 55
pineapple 46

brown rice pasta 92
gnocchi 68
linguine, durum 50
macaroni 46
macaroni & cheese 64
spaghetti 40
spag. prot. enrich. 28
vermicelli 35
vermicelli, rice 58

honey 58
jelly beans 80
Life Savers 70
M&Ms Choc. Peanut 33
Skittles 70
Snickers 41

graham crackers 74
oatmeal 55
shortbread 64
vanilla wafers 77

baby lima 32
baked 43
black 30
brown 38
butter 31
chickpeas 33
kidney 27
lentil 30
navy 38
pinto 42
red lentils 27
split peas 32
soy 18


barley 22
brown rice 59
buckwheat 54
bulgur 47
chickpeas 36
corn 55
corn chips 74
cornmeal 68
couscous 65
hominy 40
millet 75
popcorn 55
rice 47
rice, instant 91
rye 34
wheat, whole 41
white rice 88

All Bran 44
Bran Chex 58
Cheerios 74
Corn Bran 75
Corn Chex 83
Cornflakes 83
Cream of Wheat 66
Crispix 87
Frosted Flakes 55
Grapenuts 67
Grapenuts Flakes 80
Life 66
Muesli 60
NutriGrain 66
Oatmeal 53
Oatmeal 1 min 66
Puffed Wheat 74
Puffed Rice 90
Rice Bran 19
Rice Chex 89
Rice Krispies 82
Shredded Wheat 69
Special K 54
Swiss Muesli 60
Team 82
Total 76

bagel 72
croissant 67
kaiser roll 73
pita 57
pumpernickel 49
rye 64
rye, dark 76
rye, whole 50
white 72
whole wheat 72
waffles 76

Kavli Norwegian 71
rice cakes 82
rye 63
saltine 72
stoned wheat thins 67
water crackers 78

angel food cake 67
banana bread 47
blueberry muffin 59
bran muffin 60
Danish 59
fruit bread 47
pound cake 54
sponge cake 46
tofu frozen 115 Dairy
chocolate milk 34
ice cream 61
ice cream, low fat 50
milk 34
pudding 43
soy “milk” 31
yogurt 36


Note: The numbers represented are in reference to glucose, which is valued at 100, and are meaningful only in relation to this base number. They do not correspond to calories or portion size. Cooked vegetables tend to release their sugar faster than when raw, and a food’s degree of ripeness can affect its glycemic number.


These numbers are compiled from different sources and will not be identical to other glycemic indexes. (Some lists use white bread for the reference point of 100.)


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