Your brain is a sugar thief.
Whether you’re solving a tricky math problem, engrossed in a hobby, daydreaming, or fast asleep, 200 billion neurons—brain cells responsible for thought and for communication with nerves throughout your body—are firing away. Neurons produce electrical signals and send them along miles of nerve pathways throughout your body; they also assemble and release neurotransmitters to communicate with each other. Some 10,000 different types of neurons are hard at work between your ears right now, processing information that makes every aspect of human life possible, from composing music to breathing, from holding a conversation to walking down the street.
All this brain work requires lots of fuel. Brain cells gobble nearly twice as much blood sugar as any other type of cell in your body—using about 80 milligrams of sugar per minute, compared with about 50 milligrams per minute for the rest of your body at rest. And brain cells are greedy: Neurons and the helper cells that feed them, called glial cells, store only a tiny percentage of the sugar the brain needs. Without a constant supply from your digestive system and liver, delivered via your bloodstream, your brain would run short in about 10 minutes.
Keeping hungry neurons fed and energized is one of your body’s top priorities. You play an important role, too. Your little gray cells will work better—or worse—depending on the quality and quantity of carbohydrates you eat. If you’ve had any of these experiences, you’ve learned firsthand how the fuel you take in can profoundly affect your ability to think well.
• You wake up so groggy that making coffee feels like a final exam in advanced particle physics. Somehow, you assemble breakfast: cereal, milk, juice, java. Ahhh! Twenty minutes later, the mental fog lifts. Your thinking is sharp and clear.
• You’re halfway through a complicated work project, and your mind just won’t budge. Your body isn’t tired, but your brain—at least the part you need right now—is wrung out.
• You skipped lunch and wish you hadn’t. You feel shaky and can’t think straight. You grab a cola and a candy bar and … whoosh! Clarity returns (for a little while).
Blood sugar fluctuations profoundly influence your thinking over the short term and can alter the health of your brain and its ability to process and recall information over the long term. Low blood sugar can dull your mental edge if an important prelunch meeting drags on for too long. Over time, high blood sugar and related sugar-control problems can change the brain itself—raising the risk for memory lapses, dementia, and even Alzheimer’s disease.
Read on for the latest research breakthroughs on the brain/blood sugar interface. This food for thought could help you think more clearly today and for decades to come.
If you’ve ever wondered why you can hit a wall when you think about something for too long, neuroscience may finally have the answer. Landmark research has found that the hippocampus—a region of the brain crucial for processing short-term memory—may use up its glucose supply faster than other regions during intense problem solving, says neuroscientist Paul Gold, PhD, a professor at the University of Illinois in Champaign. In lab studies, Dr. Gold found that rats given glucose shots actually showed low glucose levels in this important region after navigating a new maze. He also discovered that the brains of older rats needed more time to recover after sugar supplies dropped.
Sugar is brain food. In another study by Dr. Gold, women and men in their sixties received either a sugar-sweetened or saccharin-sweetened drink after fasting overnight. After each drink, they were given an hour-long series of standardized memory tests while their blood glucose levels were monitored. “On the day our subjects got the sweetened drink, they performed 20 to 30 percent better on the memory tests,” Dr. Gold says.
These findings shouldn’t send you to the nearest Krispy Kreme shop, however. Yes, the simple sugars in a doughnut or a candy bar can spike your blood sugar—and perhaps your mental acuity—for a short time. Dr. Gold says that while certain doses of glucose improve memory and learning ability, higher doses actually impair memory. The optimal dose for improving memory probably varies from person to person, with other foods you’ve eaten recently, and even with your stress level at the moment.
The best fuel mix: good carbs—whole grains, fruits, and veggies. When University of Toronto researchers checked the memories of volunteers who breakfasted on plain water or on cereal, milk, and grape juice, they found that the cereal eaters remembered 25 percent more facts. And when breakfasters had either a sugary lemon drink or a bowl of barley, the barley eaters outperformed the sweet-drinks group on tests of long- and short-term memory.
Could it be that depression triggers or contributes to the development of diabetes?
Researchers at Kaiser Permanente Center for Health Research in Portland, Oregon, compared 1,680 HMO members newly diagnosed with diabetes and 1,680 members of the same age and sex without the condition. They found that people with diabetes were more likely than those who were diabetes-free to have been treated for or diagnosed with depression before they were diagnosed with diabetes. Moreover, when depression coexisted with diabetes, depression was diagnosed first 73 percent of the time, says Greg Nichols, PhD, senior research associate at Kaiser.
While experts aren’t sure what to make of the link, they do have theories, says Dr. Nichols. There may be a relationship between the regulation of glucose and levels of various hormones responsible for depression, like catecholamine and serotonin. “In other words, both depression and diabetes share a common antecedent,” says Dr. Nichols. “Obesity, a sedentary lifestyle, and poor diet—plus some genetic predisposition—lead to depression and diabetes, at least in some people. The big unanswered question is whether diabetes can be prevented by treating depression or even whether treating diabetes eases depression.”
Beyond hungry, you’re cranky, barely able to think clearly, and nearly on the verge of fainting. Your best bet? A glass of orange juice to raise your blood sugar swiftly and a peanut-butter-on-whole-wheat sandwich to keep levels steady ’til lunch.
Low blood sugar—doctors call it hypoglycemia—can leave you jittery, nauseous, shaky, and even sweaty and confused. If you have diabetes and use blood sugar–lowering medications, your dose may be off, or you may not have eaten enough at your last meal. If you don’t have diabetes, you may have reactive hypoglycemia (when blood sugar levels plummet an hour or two after a meal) or fasting hypoglycemia (when levels fall steadily for hours after eating).
Reactive hypoglycemia may be a sign that your blood sugar control system overreacts to the stress hormone epinephrine or that your body doesn’t release enough stored blood sugar between meals. Gastric bypass surgery and a rare enzyme deficiency, hereditary fructose intolerance, may also be behind it.
If you have fasting hypoglycemia, the cause could be a medicine you take (such as sulfa antibiotics and large, regular doses of aspirin) or the wine you had at your last meal. Your doctor may also check for a variety of kidney, heart, and liver conditions that can lower blood sugar.
The best Rx for garden-variety low blood sugar: Don’t go more than 3 hours during the day without eating—include small snacks between meals. Go for high-fiber foods like whole fruit instead of fruit juice (except when you need to raise your blood sugar quickly), whole wheat instead of white bread, nuts instead of a snack cake. Avoid sugary goodies, especially on an empty stomach.
A small but well-designed study from New York University recently made headlines (and may have changed what a lot of middle-aged folks ordered for lunch that day) with the news that middle-aged and elderly people with blood sugar trouble actually had more memory problems and a smaller hippocampus.
First, the researchers gave 30 study volunteers, ages 53 to 89, a memory test. They were told a story and, after a short period of distraction, asked to retell the story with as many details as possible. The next day, after a good night’s sleep but before breakfast, they received about two doughnuts’ worth of glucose intravenously. Then researchers evaluated how quickly their bodies used the glucose and later imaged their brains with an MRI.
The result: People with insulin resistance, who had a tougher time absorbing sugar into cells, had smaller hippocampuses. This suggests that insulin resistance not only affects the way the brain processes information but also can change the physical structure of the brain itself. The researchers said that they detected insulin resistance in the hippocampus about a decade before this memory-processing center showed signs of shrinking.
The researchers have even developed a brain-scanning computer program that can predict Alzheimer’s risk nearly a decade in advance. The system uses measurements of glucose uptake in the hippocampus. In a long-term study that followed 53 volunteers for 9 to 23 years, the researchers found that those whose brains used 15 to 40 percent less glucose went on to develop memory problems ranging from mild impairment to Alzheimer’s disease.
The research may have special significance for people with diabetes, who have a twofold higher risk for Alzheimer’s disease and are at higher risk for age-related memory loss. When Harvard Medical School researchers tested the memory and mental function of 2,300 women in their seventies, those with diabetes were twice as likely to have low scores. Investigators estimate that diabetes adds at least 4 years to the age of the brain. Taking steps to lower blood sugar in middle age—via diet and exercise—could preserve your brain.
Freelance writer Pamela Oldham of Ashburn, Virginia, writes about health for a living, yet it took an ambulance ride to recognize her blood sugar problem.
Oldham often felt sluggish in the morning, but one day in fall 2002, she dialed 911. “I began to feel as though I was about to lose consciousness,” she recalls. “My daughter was at school, and my husband had just left for work. My symptoms were strokelike, and that worried me, especially because I was alone in the house.”
By the time the ambulance arrived, Oldham’s speech was slurred and she couldn’t think clearly. En route to the hospital, an emergency medical technician thought to test her blood sugar level. It was dangerously low. He immediately began a solution of intravenous glucose. By the time they reached the medical center a few minutes later, her symptoms had all but vanished.
Although she’d never been diagnosed with hypoglycemia (low blood sugar) before, she’d had the symptoms, including dizziness, nausea, and sluggishness, for years. The morning she dialed 911, she hadn’t eaten breakfast. “I felt awful from the moment I woke up,” she says. “I was dizzy, as if I had a hangover or hadn’t had enough sleep, yet I also felt shaky and nervous. It was weird.”
The previous night, she’d eaten a candy bar before bed, which caused her blood sugar to rise, plummet as she slept, and bottom out just before she woke up.
To regulate her hypoglycemia, Oldham now eats several small meals throughout the day and tries to avoid simple sugars like candy and chocolate, especially on an empty stomach or late at night. In the morning, she eats mostly carbohydrates, such as high-fiber cereal and whole grain toast, to help steadily raise her blood sugar levels. If she starts to feel shaky, she downs a glass of orange or apple juice to balance her blood sugar.
“I’m much more aware of what I eat and drink and when,” says Oldham. “I have to admit that even with the scare I had, it was tough to change my habits—like fitting breakfast into my day. But now I know a good breakfast is a must.”