By Blaun, Randy; Wiesenack, Andreas
You are, as the expression goes, what you eat. After all, the very tissues of your body, the fuels that power every cell, the hormones that keep you humming, all must ultimately be furnished by the foods you eat. The idea that the right foods, or the natural neurochemicals they contain, can enhance mental capabilities — help you concentrate, tune sensorimotor skills, keep you motivated, magnify memory, speed reaction times, defuse stress, perhaps even prevent brain aging — is not idle speculation.
Nutritional neuroscience, as it's called, is barely in its infancy. But it's already turning up some very heady findings. Among them:
o A diet that draws heavily on fatty foods and only lightly on fruits and vegetables isn't just bad for your heart and linked to certain cancers — it may also be a major cause of depression and aggression in North America. Such a diet is particularly common among men.
o The health of your brain depends not only on how much fat you eat but on what kind it is. Intellectual performance requires the specific type of fat found most commonly in fish. Even diets that adhere to commonly recommended levels of fats, but of the wrong kind, can undermine intelligence. What makes this finding awkward is that certain oils widely touted as healthy for the heart are especially troublesome for the mind. The findings also raise serious concerns about formulas fed to the vast majority of American infants.
o It's possible to boost alertness, memory, and stress resistance by supplying food components that are precursors of important brain neurotransmitters, but so far they have only been tested on people with nutritional deficiencies. However, given the number of women who regularly diet, that group may include more people than researchers imagined.
o Sugar can make you sharp-if you can figure out the right dose at the right time. A kind of Gatorade for the mind may be available in the U.S. within a few years.
o Carbohydrates — especially when eaten with no protein or fat — may indeed be mentally soothing.
o Mood and mental performance are powerfully influenced by the B vitamins. Unfortunately, marginal deficiency in many B vitamins is widespread in North America.
While it's easy to dismiss the intensifying interest in nutrition as a selfish search for the formula or supplement that will turn us into Einsteins and confer that competitive edge, there's evidence that we're also seeking more. An abiding interest in the nutrient qualities of the foods we consume — even if honored more in the breach than the observance — also reflects our deep yearning for reconnection to the natural world and heightened awareness of how it sustains us. Call it deep nutrition.
The Sludge Factor What is the blood fat-depression connection? In a word, viscosity. A high triglyceride level increases blood sludginess, says Charles Glueck, M.D., medical director of the Cholesterol Center of Jewish Hospital in Cincinnati. It's harder for blood to transport sufficient oxygen to brain cells. Under such conditions, mini brain lesions and blood clots may form. Those affected may exhibit symptoms of so-called organic brain syndrome, among them depression and hostility.
Lowering triglyceride levels normalizes serum viscosity and reverses cerebral oxygen deficiency. Other investigators have also observed a positive correlation between triglyceride values, hostile acts, and a domineering attitude. In addition, lowering triglyceride levels improves scores on dementia screening tests in elderly patients. What's more, regimens such as the Pritikin diet, aimed at lowering triglycerides and cholesterol, also reduce depression and hostility, suggesting that cholesterol-lowering medications are not the mood-altering factor.
Obviously, not all psychological or psychiatric disorders are attributable to triglycerides and saturated fats, notes Glueck. Nevertheless, his research suggests that high blood-fat levels can be the sole cause of depression in some cases, and that they may exacerbate mental problems due to other causes. Consequently, Glueck recommends that anyone with a psychiatric problem or who is suffering from depression should have his or her cholesterol and triglyceride levels tested.
Fats and Smarts A diet high in saturated fat not only can make you depressed and downright antisocial, it can also impair general mental performance. So will a diet high in total fat and one that is deficient in essential fatty acids (EFAs). Once dietary fats are broken down into fatty acids, the body uses them for myriad purposes. They go into all hormones. They are critical to body metabolism. And they are also a constituent of the outer membrane of every cell in the body, including those in the brain.
Of the numerous fatty acids the body uses, two are called "essential" because they cannot be manufactured in the body; they must be supplied by daily diet. These arelinoleic acid, or n-6, and linolenic acid, or n-3; both are super-unsaturated fats. (You need only about a tablespoon of EFAs daily.)
N-3 fatty acids–popularly called omega-3s–are known to be particularly crucial for proper development of the human brain, both before birth and in infancy. It is through the lipid-rich cell membrane of neurons that all nerve signals must pass. In addition, as learning and memory forge new connections between nerve cells, new membranes are formed to sheath them. All brain cell membranes continuously need to refresh themselves with a new supply of fatty acids.
Preliminary research suggests that EFAs — particularly n-3s — are best suited for optimal brain function. In a key animal study soon to be published, Carol E. Greenwood, Ph.D., and colleagues fed rats various amounts and types of fat for a three-month period and then measured their performance on memory tests. Fat content ranged from 40 percent of calories — approximating that of the average American — to 10 percent of calories. Rats fed the high-fat diet that was highest in saturated fat (from lard) performed the worst. Those on the diet lowest in saturated and total fat did the best.
The old saw about fish being brain food is true; they are rich in n-3s. Long a proponent of adding more n-3-rich fatty fish to the diet as a way to reduce the risk of heart disease, William Connor, M.D., of the Oregon Health Sciences University, contends that the special n-3s in fish oil are tailor-made for the brain. Chemically speaking, they are long-chain fatty acids, containing strings of 20 or 22 carbon atoms.
One such long-chain n-3 fatty acid, docosahexaenoic acid, is identical to that found in abundance in neuron membranes. Plants also contain n-3 fatty acids, but their n-3s are arrayed in medium-length chains. Better, Connor says, to deliver to the brain — especially during development — precisely the type of fatty acid it needs and readily absorbs.
Connor sees ample evidence that long-chain n-3s have a critical bearing on intellectual performance in humans. He cites a well-controlled study of premature infants fed by tube, either standard American infant formula or breast milk. The children given breast milk had significantly higher IQs, an advantage they maintained over the eight-year study. Their IQ superiority rests exclusively on docosahexaenoic acid, Connor insists. It's a known component of breast milk. While infant formulas sold in Japan and Europe contain docosahexaenoic acid, most American formulas do not.
N-3 fats may also have the ability to protect the brain from damage, or heal it once damage occurs. In Fish and Human Health (Academic Press, 1986), biochemist William E. M. Lands, Ph.D., cites a study demonstrating that fish oil reduced the degree of brain damage in cats experiencing cerebral stroke.
Nutrients for Neurotransmitters The brain deploys a multitude of biochemicals to carry out its many cognitive tasks and make you happy, calm, alert, relaxed, energized, or motivated. Helping orchestrate every thought, feeling, and movement are the neurotransmitters, perhaps the best known of which is serotonin, whose functions include sleep regulation and anxiety reduction. Another key neurotransmitter is acetylcholine, essential in memory formation and maintenance. And count in dopamine, epinephrine, and norepinephrine, collectively called catecholamines, which control arousal and anxiety states.
Neurotransmitters are manufactured in the body from amino acids and other substances supplied by diet. Serotonin, for example, is manufactured from the amino acid tryptophan, which, like all other amino acids is found in protein- rich foods. Dopamine and norepinephrine are derived from the amino acid tyrosine (which in turn can be made from the amino acid phenylalanine). Acetylcholine is made from the fatlike B vitamin choline, found in egg yolks and organ meats.
Only recently has ongoing research begun to detail how neurotransmitters are assembled from the foods we eat, how they decline with age, disease, environmental stress, or suboptimal dietary patterns. And science is only at the dawn of recognizing how dietary components, consumed in foods or as vitamin-like supplements, may help restore healthy levels of neurotransmitters.
Creation and utilization of acetylcholine, so crucial to memory, is a complicated process dependent on numerous enzymes, hormones, and other neurotransmitters. Scientists do know that the devastation of Alzheimer's disease results from underproduction of acetylcholine due to death of the cholinergic neurons that make it. So by consuming more choline than is normally found in the diet, can a healthy younger person perform better mentally?
While the presence of extra choline does increase the amount of acetylcholine in certain areas of the brain, says Barbara Strupp, Ph.D., associate professor of psychology and nutritional sciences at Cornell University, "that doesn't mean it has any effect on learning. Just because you have more acetylcholine available doesn't mean more will be used," unless neurons are specifically calling on it. It's different, however, in Alzheimer's patients. They have suffered neuron loss, which puts a burden on surrounding cells. "The remaining cells are firing more," says Strupp. "Maybe these people would benefit from megadoses of choline." Indeed, aging mice given choline supplements showed improvement on memory tests, and an increase in the number of dendritic spines, tiny branches on nerve cells by which they communicate with each other.
Gut Reactions At the vanguard in choline research, as in much other research on the relationship between diet and performance, both mental and physical, is the U.S. Army. Even Napoleon knew that an army marches on its stomach, although if he were alive today he might update his famous dictum by declaring that an army thinks on its stomach, too. Can choline enhance the mental and physical skills of troops?
In Food Components to Enhance Performance, a groundbreaking report produced for the army by the National Academy of Sciences in 1994, researchers pulled together what's known about food and behavior. Choline supplementation, the report concludes, enhances memory and reaction time in animals, particularly aging animals. It also enhances memory in people, scant human studies show. The most concrete evidence of the benefits of choline supplementation concern physical performance. Choline supplementation minimizes fatigue. In one study cited in the report, choline given during a 20-mile run improved running time by five minutes.
Army researchers are also looking at the effects of supplemental tyrosine, the amino acid that is the precursor to the neurotransmitters dopamine, epinephrine (or adrenaline), and norepinephrine (noradrenaline). All three help regulate levels of arousal and anxiety, and are the major players in the brain's response to stress. Environmental stress depletes the blood of tyrosine, limiting the amount available for neurotransmitter manufacture. Performance flags. But when given tyrosine supplements, soldiers exposed to high altitudes or prolonged cold do not suffer the loss of memory, lightheadedness, headache, nausea, and general malaise such stresses normally bring on.
Before you make the synaptic leap from megadosing with neurotransmitter precursors to cognitive superiority, consider this: All effects so far depend on the context. Neurotransmitter supplementation improves cognitive performance only in the face of a deficit caused by environmental stress or aging. No one yet knows whether supplementation can improve performance in people who have normal levels of neurotransmitter precursors. "Whether or not you'll sustain a benefit depends on where you start off," says Strupp. "If you have a deficit of a certain neurotransmitter precursor, then you may benefit."
To complicate matters, precursor amino acids normally compete with each other to cross the blood-brain barrier. If you eat a protein-rich meal, amino acids are delivered to the brain in an acceptable pattern. But when you take supplements of individual amino acids, in attempts to bolster a specific neurotransmitter, you monopolize the transport system. That may be counterproductive, throwing off the balance of neurotransmitters needed for all-around mental performance and well-being.
To date, the best way to get the right mix of neurotransmitter precursors, along with other nutrients that are turned into brain chemicals, "is the way they come in food," says Strupp. Still, taking extra choline may not hurt. Since it's not an amino acid, choline has no competition crossing from blood to brain, and therefore it doesn't interfere with the absorption of other nutrients. It seems to be safe in the doses used in studies — around 5 grams per day — according to Strupp. If you don't regularly eat egg yolks, organ meats, and legumes, you can get choline from lecithin. But keep in mind that choline is a fat and thus adds calories.
A Jolta Java Looking for a quick cognitive boost? Go ahead, fill up your coffee mug. Psychologist Harris Lieberman, Ph.D., of the U.S. Army Research Institute of Environmental Medicine, in Natick, Massachusetts, has been studying how to maintain alertness in soldiers. Caffeine works, says Lieberman, by blocking the neurotransmitter adenosine, which normally calms the brain. "The clearest effect of caffeine on cognition is its ability to enhance vigilance." Caffeine helps sustain attention during performance of various cognitive tasks for long periods of time. Used in moderation, caffeine appears to be safe, Lieberman says. Unless pregnant, the average person can safely use coffee and tea as a habitual wake-up call, up to his or her personal "jitter threshold."
Does Sugar Make You Sharp? The brain's source of energy is, almost exclusively, glucose, a simple sugar to which all dietary sugars and other carbohydrates are ultimately broken down. Hormones that aid memory do it by raising glucose levels. According to University of Virginia psychology professor Paul Gold, Ph.D., studies of rats and people show that glucose, whether given after a fast or after a meal, whether consumed as food or injected directly into the brain (in rats), in fact improves long-term memory.
In a recent study, Gold and colleagues gave college students a lemonade drink containing 50 grams of glucose — 200 calories' worth of pure sugar — and then subjected them to a battery of cognitive tests. Gold found that glucose measurably enhanced the students' performance, most notably in a reading retention task. Which leads directly to the question: Should you chug a glucose-laced sports drink such as Gatorade to boost your brain power a quarter of an hour before your Mensa test? Perhaps, but the amount you need to drink is still something of a crapshoot. Your optimum dose of glucose at any one time depends on several factors: current blood glucose level, physical and mental stressors, previous dietary patterns, individual metabolism, and other variables that neither you nor medical science can readily evaluate at this time.
To further complicate matters, the dose you take doesn't always match the response you want. Too much glucose can actually prompt a hypoglycemic response. Blood sugar levels soar, then plummet: in response to the sudden sugar flood, insulin rushes into the blood and mops up the excess, worsening mental performance. Still, a glucose drink specifically tailored more for brain boosts than for physical performance is already available in England and might reach American markets within the next few years, according to Gold. Most likely it will be initially targeted for the elderly, and those with Alzheimer's disease, Down's syndrome, and head injuries, all of whom perform substantially better on cognitive tests when given glucose.
How best to stoke your brain with glucose? "The variety of carbohydrate foods found in a balanced diet will take care of the brain's energy needs," says Gold. "The brain is selfish, and takes care of itself," having first dibs on any glucose present in the bloodstream. Or it may force the conversion of other nutrients into glucose.
Mood: A Serotonin Solution? Carbohydrates not only influence cognitive performance, they play a major role in your mood, contends Judith Wurtman, Ph.D., research scientist at the Massachusetts Institute of Technology. She finds that a diet rich in carbohydrates can help you feel anxiety-free and relaxed, by giving the amino acid tryptophan preferential access to the brain.
When you eat a protein-rich meal. Wurtman explains, the protein is broken down into component amino acids, some of which, like tryptophan, are neurotransmitter precursors. All of them, however, must compete to get into the brain. But when you eat a meal or snack that's mainly carbohydrates–provided it supplies less than five percent of calories from protein — insulin rushes in and, while targeted at the carbs, also sweeps up any amino acids lingering in your bloodstream from a previous protein meal. All the amino acids, that is, but tryptophan. Survivor of the insulin onslaught, tryptophan slips into the brain uncontested. Once there, it is converted to serotonin and elevates mood.
Wurtman, author of The Serotonin Solution(Ballantine, 1996), has found that women with premenstrual syndrome (PMS) dramatically increase their carbohydrate intake in the two weeks prior to menstruation, while women not subject to PMS do not. She sees this as evidence of self-medication, an attempt to increase brain levels of serotonin in order to alleviate the anxiety, depression, and concentration difficulties that characterize PMS.
Ditto individuals who develop depression and fatigue in the winter months, who increase carbohydrate intake seasonally. Carbohydrates may be calming for another reason, suggests Barbara Smith, Ph.D., assistant professor of psychology at Johns Hopkins University. Her studies indicate that the sweet taste of sugar stimulates the release of endorphins, the brain's natural opiates.
Either or both effects may account for the results seen in a study, conducted at the University of Wisconsin, of delinquent adolescent males. When subjects were fed a breakfast of cereal high in sugar, researchers documented an improvement in depressive symptoms and fewer incidents of aggressive behavior.
The Busy Bs The B vitamins consist of thiamin (B1), riboflavin (B2), niacin, pyridoxine (B6), folic acid, pantothenic acid, biotin, and cobalamin (B12). All play a critical role in brain function, from manufacturing neurotransmitters to regulating energy release in brain cells. Severe deficiencies of several B vitamins have been shown to have profound effects on the brain, leading to abnormal brain waves, detectable as abnormalities on EEGs; impaired memory; and higher levels of anxiety, confusion, irritability, and depression.
Even marginal deficiencies of B vitamins can cause EEG disturbances and inhibit mental performance, reports James G. Penland, Ph.D., a research psychologist at the U.S. Department of Agriculture's Human Nutrition Research Center in Grand Forks, North Dakota. Although many of the studies were done on older people, who are frequently deficient in vitamins and minerals, the same impairments could be expected in younger people with the same marginal deficiencies.
At the University of California San Diego Medical School, where he is professor of psychology, Philip Langlais, Ph.D., finds that thiamin deficiency hampers the brain’s ability to use glucose, decreasing energy available for mental activities. It also overexcites neurons so that they fire endlessly, poop out, and die. "If you are even marginally deficient in thiamin," says Langlais, "you may be slowing down your brain power." Folic acid, meanwhile, helps maintain normal levels of serotonin.
Deficiencies contribute to depression, dementia, and schizophrenia. In a study of depressed patients taking lithium, those also given folic acid supplements for a year showed dramatic relief of depression, compared to those given no supplements.
Oh Those RDAs Americans, it's clear, are not malnourished calorically; in fact we consume too many calories. So it is indeed ironic that in the land of plenty we may be undernourishing our brains. According to Penland, Americans' eating patterns, and especially those of women, as a result of dieting, serve up special shortages of folic acid and minerals, including iron, calcium, magnesium, manganese, copper, and selenium.
While men eat more calories than women do, that doesn't give them better brains. Studies show that they eat fewer vegetables, fruits, grains, and nuts, foods rich in key vitamins and minerals. But even consuming recommended dietary allowances (RDAs) for all nutrients may hot guarantee a robust brain. The current RDAs, says Penland, are crude measures, based on a few animal studies and on observations of what people ordinarily consume, and these allowed experts to decree minimum levels of vitamins and minerals needed to sustain normal growth, maintain immune function, and fend off death, plus a safety margin to accommodate individual differences.
But nutrient levels needed for optimal general health and brain functioning may be many times higher than current RDAs, as they were in many of his own studies, says Penland. Still, it would not be prudent to wolf down mega-amounts of vitamins and minerals. Reliable studies of the long-term effects of megadoses have yet to be done, especially of trace minerals, which can be toxic in large amounts.
Penland warns against taking doses that exceed the RDAs at this time, except for calcium, the RDA of which is widely considered too low for most women. But along with other experts interviewed for this article, he suggests that, on top of a healthful diet, you take a multivitamin and mineral supplement that supplies RDA amounts. This is particularly important for the elderly, among whom marginal deficiencies of vitamins and minerals are widespread.
THOSE AMAZING ANTIOXIDANTS Perhaps more than most organs, the brain is subject to attack from free radicals of oxygen, wildly reactive molecules given off in the normal course of events but also created by smoking, air pollution, injury, and disease. Free radicals act like biochemical bumper cars, damaging cell membranes and DNA with each collision. Cumulative damage from free radical reactions is implicated in the aging of skin, many cancers, and perhaps the aging of the human brain. "The brain consumes more oxygen than any other organ. That means it might generate more free radicals," says John Weisburger, Ph.D., senior member of the American Health Foundation and preventive medicine researcher.
Vitamin E is the body's natural antioxidant. Now recommended for heart health in amounts well over the current RDA of 12 IU (women) and 15 IU (men), it should also benefit the brain. But even a healthful diet supplies scant vitamin E, Weisburger finds. He suggests taking a daily supplement. But there's more to antioxidants than vitamin E. Substances known as polyphenols, found naturally in the leaves used in green and black tea, are many times more potent than some antioxidant vitamins, says Weisburger. He points out that five cups of tea per day supply the same antioxidant dose as two servings of vegetables.
Fruits and vegetables contain thousands of antioxidants and other natural chemicals that should help maintain brain health. Among those known so far are the antioxidants lycopene, in tomatoes; isoflavones in soy protein foods; polyphenols in red wine; sulphoraphane in broccoli; and ellagic acid in strawberries. So packing your diet with fruits and vegetables is essential.
Still, one noted researcher doesn't shy away from recommending antioxidant supplements. E. Wayne Askew, Ph.D., nutritional biochemist at the University of Utah, is high on a couple of natural antioxidants — pycnogenol®, a potent substance derived from yew tree bark, and coenzyme Q10, which is made in the body but in minute quantities. As insurance there are also new commercial phytochemical formulas, containing potent antioxidants and other substances from fruits and vegetables.
"Many brain disorders incur oxidative damage," observes Lester Packer, Ph.D., nutritional biochemist at the University of California at Berkeley. "Therefore antioxidants may be especially helpful to people already suffering brain damage, or to prevent against it. Studies with animal models and human cells suggest that antioxidants may prevent damage due to stroke."
Packer singles out lipoic acid for particular promise as a supplement. Made naturally in body cells as a byproduct of energy release, it has an "amazing protective effect" in the brain. In one study he conducted, rats subjected to strokes were given lipoic acid — 80 percent of supplemented animals survived. Packer himself downs 50 mg of lipoic acid daily. In addition, he favors supplements of another antioxidant found in the body in tiny amounts, glutathione. And he recommends "four to five" times the RDA for vitamin C. The latter, an antioxidant in its own right, also prevents breakdown of vitamin E.
Count among the antioxidants vitamin A, also needed for proper cell differentiation, growth, and reproduction. Few studies exist of vitamin A and brain function. But older people consuming adequate amounts of the vitamin A precursor beta-carotene do better on cognitive tests than those who don't get enough beta-carotene. And retinoic acid, a vitamin A derivative (cousin of the acne medication), can actually regenerate nerve cells in aging animal brains. According to the University of Toronto's Greenwood, retinoic acid is one of a handful of substances that show real potential as potent anti-aging drugs, possibly available within the next decade.
Another is a form of choline, called cytidine dephosphocholine (or citicoline), that supplies the nutrient in amounts that render it a drug. In studies by psychologist Paul Spiers, Ph.D., at the Massachusetts Institute of Technology, citicoline restored cognitive abilities to people aged 50 to 90 who scored below average for their age on a series of learning and memory tests. Given to others who had just suffered strokes, it more than doubled the proportion who eventually regained complete function.
The era of consuming nutrients to boost brain performance is only just beginning. Bon appetit.
Source: Psychology Today (www.psychologytoday.com). © Psychology Today, all rights reserved. Publication Date: May/Jun 96. This article has been edited for length.