By Elizabeth Pope
Some days it seems as though our brains don’t work as well as they once did. Scientists once assumed that these changes in brain function were inevitable because adults lost brain cells every day, and those cells could never be replaced.
But during the past decade, new discoveries about the brain have challenged that view. They show that the brain loses relatively few of its cells over time, and only in a limited number of areas, so most likely you’ll have about the same number of brain cells (called neurons) at age 70 as you had when you were 20. Even more encouraging, studies reveal that older adult brains are capable of growing new neurons, a process called neurogenesis.
Of course, age-related changes do occur. The brain’s speed in storing and retrieving information and the ability to focus on multiple tasks do slow a bit, notes neurologist Barry Gordon, M.D., Ph.D., of Johns Hopkins Medical Institutions in Baltimore.
That’s why few adults have a teenager’s ability to concentrate on homework, listen to music, and talk to a friend at the same time. But even if they can’t perform these youthful mental gymnastics, most adults can come close by making a few simple changes in their lives.
Although scores of brain-improvement books and Web sites promise “amazing results” from mental exercises, gimmicks, and games, serious researchers believe the keys to staying sharp are as simple as regular physical exercise, sound nutrition, and stimulating work, hobbies, and intellectual pursuits. If you want to beef up your brain, start with your body.
Brain Builders
What’s good advice for your general health applies to your brain as well: Get enough sleep, eat well, exercise, don’t smoke, keep stress under control, drink moderately, and monitor your medications.
Doctors also warn that undetected illnesses can cause fuzzy-mindedness. “High blood pressure, for example, is a risk factor for declining mental status as people get older,” Gordon says. “So if your blood pressure is higher than it should be, seek treatment for it.” Diabetes and plaque-clogged arteries are other underlying causes of mental decline. A 10-year study of 6,000 older adults published in the Journal of the American Medical Association showed that men and women who had both of these diseases were eight times more likely to show cognitive loss than their healthier counterparts.
“In addition, you should try to improve your aerobic capacity,” Gordon adds. “Has it been proved that aerobic exercise improves mental function? No. Is there strong evidence that it works? Yes.” Any aerobic exercise, such as walking, biking, swimming, tennis, or water aerobics, gets oxygen-rich blood pumping to your brain, the organ that requires more oxygen than any other part of your body.
Research also indicates that physical activity increases levels of a brain chemical called brain-derived neurotrophic factor, which promotes the growth of new brain cells and protects them from the age-associated damage caused by free radicals. Free radicals, the result of normal oxygen metabolism, are considered the major cause of damage to cells throughout the body, and the body’s natural defenses against them tend to weaken over time.
So far scientists studying brain cell growth have worked only with laboratory animals, but the results are promising. A study at the Salk Institute in La Jolla, California, showed that mice who ran nearly three miles a day on a treadmill grew twice as many new brain cells in the hippocampus, one of the brain’s structures, as those who lazed around their cages not doing much of anything.
Other research has shown the positive effect of exercise on human brain power. In a study at the University of Illionis at Urbana-Champaign, a group of men and women who had avoided physical activity began to take brisk walks three times a week for six months. At the end of the six months, they had significantly improved their performance on mental-function tests compared with a similar group that practiced yoga stretches and weight lifting.
The walkers scored up to 25 percent higher on tasks related to what researchers call “executive control processes,” the procedures we use to plan, schedule, and coordinate several tasks at once. “Driving a car while keeping an eye out for pedestrians, listening to the radio, and rehearsing a speech you're scheduled to give would be one aspect of executive control,” says the study’s lead author, neuro-scientist Arthur F. Kramer, Ph.D. Another example would be looking up a phone number and then dialing it, all the while carrying on a conversation with someone nearby. This kind of activity takes place in the part of the brain most susceptible to age-related decline.
No one yet knows if these cognitive benefits cease when you stop the protective physical activity. “It’s one of the many future questions we have to explore,” Kramer says. “But even if we don’t yet have all the data about the magnitude of its value and exactly which cognitive processes improve, we know exercise provides some benefits. All you have to do is walk. It’s free and there are no adverse effects.”
Feed Your Head
Fruits and vegetables are a powerful tool for keeping your brain as well as your body in top-notch shape. Those rich in antioxidants like beta carotene (which the body converts to vitamin A), and vitamins C and E can help you stay razor-sharp by fighting toxic free radicals.
Blueberries, which are packed with antioxidants, show promise of reversing age-related mental decline, though so far only in laboratory animals. When neuroscientists at Tufts University in Boston fed older rats the equivalent of one cup of blueberries a day, the rodents' mental performance improved. Spinach ranked second and strawberries third in brain-boosting benefits.
"But all antioxidants aren’t the same," says Jeffrey Blumberg, Ph.D., director of the Antioxidant Research Laboratory at the university's USDA Human Nutrition Research Center on Aging. “It’s possible that vitamin E does something that vitamin C doesn’t,” he says. To make sure you get the full range of benefits, Blumberg recommends eating a variety of antioxidant-rich foods, including citrus fruits, vegetables, and nuts.
In addition, the B-complex vitamins, B1 (thiamin), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), and B12, play an important role in brain function. Scientists have long recognized that vitamin B deficiencies associated with diseases like pellagra and beriberi caused nerve damage and mental impairment. Recent research shows that neurologic and psychiatric problems in people with low levels of vitamin B12 and folic acid (another vitamin) could be reversed if they took supplements.
“Dark green leafy vegetables like spinach are a great source of folic acid and vitamin B6," Blumberg says. Whole-grain breads, flours, and cereals enriched with folic acid are also good sources of these brain-building nutrients.
As for vitamin B12, up to 30 percent of people over 60 don't absorb it from food very well, so they may have to depend on a supplement. Sufficient amounts of vitamin E, found in vegetable oils, wheat germ, and nuts may also be difficult to obtain through food alone. That's why many nutrition experts suggest a supplement. "Your first line of defense is eating well, but supplements are like seat belts," Blumberg says. For most people it's perfectly safe to take a daily multivitamin pill that provides 100 percent of the recommended daily intake (RDI) of vitamins and minerals plus another 400 I.U. of vitamin E and 100 percent or more of vitamin B12. But if you're taking medication or coping with any disease, check with your doctor first.
Challenge It or Lose It
A steady diet of challenge and stimulation, what neuroscientists call an enriched environment, also helps you stay quick-witted. Brain cells thrive on stimulation and shrivel up without it. So challenge your brain to make new connections by staying curious and creative.
Although they don't know why, researchers have long recognized that education helps protect against the loss of mental faculties. The more years of education you have, the higher the level of mental activity and the less the chance of age-related decline. Using your noggin builds up what neuroscientists call brain reserve, an extra capacity that helps maintain mental acuity into old age.
The latest laboratory research with animals shows that the brain actually responds to new challenges by growing longer dendrites, the branchlike part of a neuron that picks up the chemical signal by which brain cells communicate with each other. Scientists once thought that dendrites grew only in children's brains, but recent work shows that older nerve cells can also sprout dendrites, and researchers wonder if lifelong learning in older adults might enhance brain development.
“We don't know if increased intellectual activity later in life has an effect, but it's plausible that it does,” says Richard Mohs, Ph.D., professor of psychiatry at the Mount Sinai School of Medicine in New York City. "So people in their 50s, 60s, and 70s may benefit if they become more involved intellectually."
In just four days of exposure to a stimulating environment, rats show brain improvements, says Marian C. Diamond, Ph.D., a neuroanatomist at the University of California-Berkeley. Rats exposed to a mini-playground of little wheels, mazes, and ladders developed a thickened cerebral cortex, larger nerve cells, longer dendrites, and improved nerve synapses. But dendrites shriveled in the brains of rats placed in barren cages.
Although no one's suggesting that you buy a swing set for your backyard, you can challenge your mind with interesting courses, discussion groups, travel, and other such activities. And studying a foreign language sets off "dendritic fireworks" in adults, says UCLA neurobiologist Arnold B. Scheibel, M.D.
Further evidence of the value of complex activities comes from a 30-year nationwide study of several hundred husbands and wives carried out by the National Institute of Mental Health (NIMH). It showed that people with complex work or leisure activities performed better on cognitive tests than their peers who worked in monotonous jobs.
The researchers defined complexity as activities that demanded a lot of difficult decisions and a variety of approaches to making judgments or solving problems. But even something as seemingly mundane as housework earned high marks if performed with initiative, self-direction, and creative flare. On the other hand, closely supervised workers in routine jobs may lose intellectual flexibility to some degree.
"We're not sure why it happens, but we know that it does," says the study's lead author, Carmi Schooler, Ph.D., a psychologist at NIMH. "It's a two-way street. The less complex the activity, the less the results."
For that reason, researchers who study successful aging recommend that if you retire from an exciting, demanding job, you should adopt challenging volunteer work or hobbies—and put that brain of yours to good use.
Elizabeth Pope wrote “Bye-Bye Blahs” for our July/August 2000 issue.
