May 16, 2013

The effect of food on brain activity

Your brain is always hungry. Second by second, minute by minute, hour by hour, it voraciously devours the protein, carbohydrates, fats, vitamins, and minerals you eat, then turns them into the membranes and chemicals your brain uses to learn, think, feel, and remember.

How does the brain get its nourishment? Well, let's say you had a steak, baked potato, and salad for dinner last night. The protein from your steak went straight through your stomach to your intestines, where it was broken down into amino acids. The amino acids were absorbed into your bloodstream, then circulated throughout your body to power your muscles and organs. When they got to your brain, however, not all of these amino acids were welcome. No, the brain is as selective as a New York nightclub. When the doors open, only those at the head of the line are permitted in. And if a particular amino acid isn't up front and noticed, chances are it will be ignored and left standing at the door. And just like the nightclub scene, who gains entrance will help set the mood for the night.

Why Amino Acids Are Amazing
In the brain there are two amino acids that compete with one another to enter. One is tyrosine, which your brain uses to make the neurotransmitters dopamine and norepinephrine, two electrically charged chemical messengers that are crucial to quick thinking, fast reactions, long-term memory, and a feeling of being alert and in control. The other is tryptophan, which your brain uses to make the neurotransmitter serotonin, a chemical messenger that slows your reaction time, impairs concentration, makes you sleepy, and reduces the need to be in control. On the nightclub circuit, tyrosine would be the life of the party and tryptophan the party pooper.

How do these two amino acids affect the activity going on in the brain? If tyrosine gets to your brain first, it will stimulate production of the neurotransmitters that spark mental performance - you'll be ready to function at peak intellectual levels all night long. But if tryptophan gets in ahead of tyrosine, serotonin will steal the show - mental performance will wane and your brain will prepare to shut down early.

To Stay Alert, Reach for the Protein first
Many scientists believe that you can control the activity level of your mind with the food that you eat. One scientist on the forefront of this theory is Judith Wurtman, Ph.D., a researcher at the Massachusetts Institute of Technology (MIT) and author of Managing Your Mind and Mood through Food.

If you want the stimulating effects of tyrosine, she advises, eat the protein portion of a meal (such as meat) before you take a single bite of anything that contains carbohydrates. If you're eating a normal-sized meal, this would be about 3 ounces of meat.

Protein is loaded with tyrosine but only modest amounts of tryptophan, which means tyrosine wins out when it comes to getting to the brain first. It takes carbohydrates to get the tryptophan to the brain, she explains. Just 3 or 4 ounces of protein - meat, fish, or poultry will send tyrosine zipping off to your brain while the tryptophan lies in wait for the carbohydrates - such as breads, pastas, and potatoes - still sitting on your plate.

If you ate half of last night's steak before you started on the potato, for example, tyrosine would have "made it past the door" and your mind would have been ready for action. If you ate only the potato, ten to one you'd wish you had never left home.

Tyrosine Can Clear a Muddled Mind
Tyrosine's ability to boost mental performance is so powerful it may even be able to overcome the mind-muddling effects of stress.

In a study conducted at the U.S. Army Research Institute of Environmental Medicine in Massachusetts, researchers found that tyrosine countered the effects of stress on the mental performance of soldiers. Twenty-three soldiers between the ages of 18 and 20 participated in the study, which simulated suddenly airlifting them to 15,500 feet (roughly equivalent to a fast trip up the side of Pike's Peak in the Colorado Rockies) under chilly conditions.

The simulation was done twice, once after half the soldiers had been given a tyrosine capsule and half had been given a placebo (inert pill), then once again so that those who had received the tyrosine now got a placebo and those who had received the placebo got tyrosine.

On the morning of each simulation, the soldiers, given either tyrosine - equal to about 80 percent of a day's normal intake of protein - or a placebo, were left in the test situation for 4 1/2 hours. During each simulation they were given a battery of tests that determined their ability to translate messages into code, chart coordinates on a map, think clearly, and make decisions.

The result? Soldiers who normally experienced stress - headaches, fatigue, muddled thinking, poor performance, depression, and tension - under these conditions found that tyrosine diminished that stress. Soldiers who normally did not find these conditions stressful, however, found that the tyrosine did not affect them one way or the other. But researchers were not surprised.

"You have to be sick or ill or showing the effects of the [stress] condition before tyrosine can be of benefit," explains Louis Banderet, Ph.D., the research psychologist who led the study. "But that shouldn't be too surprising. If you were testing a treatment for cancer, you would not expect it to benefit people unless they were showing the effects of cancer."

Protein Is the Real Power Lunch
Find it hard to believe that you can turn your brain on and off so simply? Scientists have had their doubts as well, particularly regarding the effects of carbohydrates. But in a study conducted at MIT (which has since been duplicated), scientists feel they have finally established a strong case in favor of the theory.

In one study, researchers gave 40 men between the ages of 18 and 28 a large portion of turkey breast for lunch, then asked them to do some complicated mental tasks. On another day, they gave the same men an equivalent number of calories in the form of wheat starch - almost pure carbohydrate - then gave them another set of mental tasks. The result? Mental performance was "significantly impaired" after the carbohydrate meal. But it was fine after the protein lunch.

Carbos Cause Double Trouble after 40
Another study, conducted at Harvard University, indicates that the effects of carbohydrates on the brain are even more dramatic in those over the age of 40. In that study 184 men and women were fed either the same protein-rich turkey used in the other studies or sherbet, which, like the wheat starch, is almost pure carbohydrate. The result of this particular experiment? Much the same as the others, except that scientists also discovered that people over the age of 40 who ate the sherbet had up to twice the difficulty concentrating, remembering, and performing mental tasks as those who had eaten the turkey. People under the age of 40 were less likely to be affected.

Eat Carbohydrates to Unwind
Carbohydrates, of course, aren't all bad. In fact, in some situations they can be all good. Remember, scientists say that carbohydrates can slow down your brain. If you've had a long, stressful day and all you want to do is go home, stretch out on the couch, and watch the news, carbohydrates can actually help you unwind.

According to Dr. Wurtman, just 1 ½ ounces of a carbohydrate is sufficient to relieve the anxiety and frustration of a stressful day.

In a study jointly conducted by the Chicago Medical School, Temple University, and Texas Tech University, seven healthy women between the ages of 18 and 29 were fed either high protein, high carbohydrate, or a combination of the two for lunch on different days. Blood samples were drawn several times after each lunch, and the women were given tests that measured several factors, including their fatigue and activity levels.

Drowsiness among women who ate the high-carbohydrate lunch was almost twice that of women who ate the other lunches, reported the researchers. And their activity levels were cut by 46.7 percent.

Carbohydrates Stimulate SAD People
Interestingly, however, eating carbohydrates has the opposite effect on someone who suffers from seasonal affective disorder (SAD), mental disorder characterized by lethargy and depression during the fall and winter seasons. The disorder is linked to shortened daylight hours.

In a study conducted at the National Institute of Mental Health, for example, 16 depressed adults with SAD and 16 healthy adults were each given a high-protein lunch of turkey salad one day and a high-carbohydrate lunch of specially prepared cookies on another. After each lunch, study participants were given blood tests to measure the amount of tryptophan and tyrosine in their blood and another series of tests that indicated mental function and mood.

The results were nothing short of astounding to the researchers, who had come to expect the calming effect of carbohydrates: Not only did the adults with SAD not become fatigued after eating the carbohydrate-loaded cookies, they actually became invigorated. As a result, scientists are now beginning to suspect that some biochemical abnormality in the brains of people with SAD is what causes the disorder and that the abnormality may be corrected by eating carbohydrates.

The Tryptophan Problem
Notice that, in all this talk of carbohydrates, researchers are discussing the effects of tryptophan as it occurs naturally. Nobody is talking about tryptophan supplements, which were linked in 1989 and 1990 to a number of deaths from a blood disorder known as eosinophilia-myalgia syndrome (EMS). As a result, manufacturers were asked by the federal Food and Drug Administration to withdraw the supplements from the market.

Although an investigation uncovered the possibility of tainted supplements, there appears to be another good reason to avoid tryptophan supplements. Taking supplemental tryptophan to induce sleep may actually carry side effects similar to those of sleeping pills. "I think that tryptophan has the potential to be addictive," says Joe Tecce, Ph.D., a neuropsychologist at Boston College who has been studying tryptophan for more than five years. He told how he and his staff took moderate amounts of the supplements while conducting nutrition and sleep studies at the Human Nutrition Research Center on Aging at Tufts University. "We found that the morning after we felt like we had hangovers. We all agreed – independently - that we needed that second cup of coffee right away to get started in the morning." And, he adds, "It seems that some of my students at Boston College got hooked on tryptophan to go to sleep."

Interestingly, a full year before the tryptophan-related deaths were reported, Dr. Tecce presented a paper to the American College of Neuropsychopharmacology which indicated that supplemental tryptophan does not seem to be the innocuous substance it was first thought to be.

It Takes B, to Work
Aside from rousing his suspicion that supplemental tryptophan's effect is both drug-like and addictive, Dr. Tecce's work has also revealed a lot about how tryptophan works in the brain. Not only has he confirmed that it can make you sleepy, but he also discovered that it has little if any effect unless it's teamed up with vitamin B6.

What does this mean to you? It means that you can eat all the carbohydrates in the world to unwind, but it won't do your brain much good unless your diet contains good sources of B6, such as avocados, bananas, kidney beans, turkey, fish, and most vegetables. (Boost Your Brain Power, by Ellen Michaud, Russell Wild and the editors of Prevention Magazine)