Diet, Mood, and Behavior

THE timing and contents of meals, as well as the consumption of certain individual nutrients, can have subtle and occasionally dramatic effects on mood and behavior, according to a series of new studies described at the Massachusetts Institute of Technology last week.

Several of the studies indicate that foods and nutrients might be used therapeutically to treat such common problems as depression, insomnia, hyperactivity, chronic pain and carbohydrate cravings.



The evidence presented, which shows that specific foods and nutrients can produce specific changes in the chemical balance of the brain, also suggests that diet might be tailored to suit the task at hand. For example, the research indicates, it might be best to consume a high-protein, low-carbohydrate meal before doing a complicated job that requires concentration and alertness.

The studies cast strong doubt on the currently popular beliefs that sugar makes children hyperactive and that sugar-free diets can curb aggression in prison inmates. On the other hand, the new studies lend scientific support to the popular notion that the way people feel is affected by what they eat. They also give credence to such folk wisdom as the use of candy to soothe a crying child and of hot milk and honey to induce sleep.

"It's likely that early in life people make associations between the consumption of certain foods and changes in how they feel," said Dr. Richard J. Wurtman, a neuroendocrinologist at the Massachusetts Institute of Technology and chairman of the conference. "Then, later on, they unconsciously turn to those foods to re-create the desired feelings."

For example, several studies demonstrated that eating carbohydrates (sugars and starches) can raise the level of a brain chemical, serotonin, that is associated with feeling relaxed, calm, sleepy, less depressed and less sensitive to pain.

This may be why so many people report that they binge on carbohydrates when they feel anxious or depressed, noted Dr. Judith J. Wurtman, a cell biologist and nutritionist at M.I.T. and the wife of Dr. Richard Wurtman.

"It may also explain why high-protein, low-carbohydrate weight-reduction diets usually fail," she went on. "These diets induce a serotonin deficiency in the brain which in turn could trigger carbohydrate cravings to correct the imbalance."

Dr. Wurtman has found that very low doses of the drug fenfluramin, which raises brain serotonin levels, can help curb carbohydrate binges. She has also formulated "The Carbohydrate Craver's Diet," which incorporates sweet and starchy snacks into a low-calorie eating plan. It will be published as a book by Houghton Mifflin in January.

The research reported here is largely an outgrowth of neurochemical studies by Dr. Richard Wurtman, Dr. John D. Fernstrom, also of M.I.T., and others that found that the consumption of certain nutrients can change the levels of brain chemicals that transmit messages between nerve cells. These neurotransmitters, as they are called, regulate a wide variety of brain activities and can affect both mood and performance. The nutrients are actually the chemical precursors, or parents, of neurotransmitters, which cannot be given directly because they do not cross into the brain from the blood.

For example, tryptophan, an amino acid found in protein foods like meat, chicken and fish, is the precursor of serotonin, a neurotransmitter that induces sleep and acts as an antidepressant. When tryptophan is given or when foods are eaten that raise the blood levels of tryptophan, serotonin levels in the brain increase.

Although tryptophan is a constituent of protein, it is the consumption of carbohydrate foods that actually raises tryptophan levels in the blood and brain. This occurs because other amino acids in protein successfully compete with tryptophan for passage into the brain, and brain levels of tryptophan and, in turn, serotonin, fall when protein is eaten.

Carbohydrate foods like sweets, bread, pasta and rice, on the other hand, result in removal from the blood of the competing amino acids and a consequent increase in tryptophan and serotonin levels in the brain.

Among the other findings described here were these:

* Newborn babies fall asleep more readily when tryptophan and carbohydrate are added to their formulas, Dr. Michael W. Yogman of Children's Hospital Medical Center in Boston reported. It may eventually be possible to adjust a nursing mother's diet or tailormake formulas to help babies sleep through the night and be more alert during the day, he suggested in an interview.

* Tryptophan also induces sleepiness in adults, Dr. Ernest Hartmann, a sleep specialist at Tufts University School of Medicine, reported. He and Dr. Harris Lieberman, a psychologist at the Massachusetts Institute of Technology, suggested that tryptophan might be used to treat mild insomnia without producing the moodaltering effects and central-nervous-system depression caused by barbiturates and other sleep-inducing drugs.

* Tryptophan also appears useful in combating pain, again without producing unwanted side effects. Dr. Lieberman reported that this amino acid reduced sensitivity to pain. A study at Temple University found that patients suffering from chronic facial pain experienced significant relief when treated with tryptophan and a highcarbohydrate, low-protein, low-fat diet for a month, Dr. Dorothy Dewart reported.

* Tyrosine, an amino acid (from protein foods) that is the precursor of the neurotransmitter norepinephrine, has shown promise in combating depression, according to preliminary studies described by Dr. Alan J. Gelenberg, a psychiatrist at Harvard Medical School.

Norepinephrine and serotonin are believed to play major roles in mental depression, and nearly all drugs now used to treat depression increase neurotransmission by one or both of these brain chemicals. The consumption of particular foods is not helpful in this case; tyrosine must be given directly to achieve an adequate blood level.

* Children who are high consumers of caffeine (in soft drinks and iced tea) were described as more nervous, more hyperactive and more easily frustrated and angered than were children who typically consumed less of this stimulant, according to Dr. Judith Rapoport of the National Institute of Mental Health. Caffeine blocks the brain chemical adenosine, which ordinarily acts like a tranquilizer by interfering with the transmission of messages from one nerve cell to another.

Dr. Rapoport also reported that, contrary to the popular impression, sugar had a calming effect on the children she studied, a finding that fits in with the known effects of carbohydrates on serotonin levels in the brain.

This raises serious questions about the use of low-sugar diets to treat hyperactive children and to calm prison inmates. Although one such plan, sometimes called the Oklahoma prison diet, has been instituted in a number of prisons, Dr. Richard Wurtman said it was not based on scientifically derived facts and made no biological sense in light of the sedating effect of carbohydrates.

He also suggested that the stimulation of coffee in the morning might help counter the sleepiness induced by such typical highcarbohydrate breakfasts as orange juice with a sweet roll or toast and jam or sugared cereal.

The effects of nutrients on mood and behavior depend in part on age and sex and on the time of day they are consumed, according to Dr. Bonnie Spring of Harvard.

Her studies at the United States Army Research and Development Laboratories in Natick, Mass., indicate that women feel sleepier and less vigorous than men do after eating a carbohydrate meal; men report feeling calmer. Among people aged 40 and older, a high-protein breakfast made them feel more tense, more angry and less calm than a high-carbohydrate breakfast. However, a high-carbohydrate lunch interfered with their ability to perform tasks that require sustained attention or concentration.

Dr. Spring and Dr. Richard Wurtman noted that foods eaten on an empty stomach had more dramatic effects. Thus, Dr. Spring said, "the effect of lunch is likely to be less than that of breakfast." Dr. Wurtman added that "if you are still digesting a high-protein meal, the effects of tryptophan or carbohydrate foods will be muted."

Other studies point to the overall value of eating breakfast. Dr. Ernesto Pollitt of the University of Texas School of Public Health in Houston reported that children who skipped breakfast were less able to solve problems and made more errors, especially late in the morning, than breakfast eaters.

However, "you can't just talk about breakfast as if all breakfasts were the same," Dr. Wurtman commented, adding, "A highcarbohydrate breakfast is likely to have a different effect than one that is high in protein or that contains a good balance of these nutrients."