PUBH 1517 - (Chapter 13) Food, Mind & Memory

PUBH 1517 - (Chapter 13) Food, Mind & Memory -...

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Unformatted text preview: Food, Mind, & Memory Memory Chapter 13 Controversy Brain Terms Brain Blood­brain barrier: tightly spaced cells lining the blood vessels in the brain. Blood­borne substances must enter the brain by way of the cells, because they cannot pass between the cells. Neurotransmitter: chemical messenger released by a nerve cell when it is conducting a nerve impulse Communication within the Brain More brain terms More Catecholamines: neurotransmitters made form the amino acid tyrosine (dopamine, epinephrine, norepinephrine) Serotonin: one of the brain’s principle neurotransmitters, made from the amino acid tryptophan Precursor control: control of a compound’s synthesis by the availability of that compound’s precursor. More precursor ­> more synthesis. Nutrients Especially Important to Brain Function to Amino acids for synthesis of neurotransmitters Iron, B6, riboflavin needed for steps in synthesis of neurotransmitters Lipids: amount and type have been shown to affect brain function Dietary Influences on Serotonin Dietary Synthesis is precursor­controlled, so depends on amount of tryptophan available Availability of tryptophan to brain depends on how much competition it has in getting past the blood­brain barrier Competition from other amino acids is influenced by the insulin level, because insulin drives other amino acids, not tryptophan, into other body cells, leaving tryptophan with less competition for entering the brain cells Diet & Serotonin, cont. Diet Typical mixed meal does not have significant impact on serotonin levels, due to containing several other amino acids besides tryptophan Ingestion of high carbohydrate, low protein meal or snack is most effective way to promote entry of tryptophan into the brain, & thus promote synthesis of serotonin Effects of Serotonin Effects Theoretically, can have a bearing on what food is chosen next time a person eats. When serotonin is elevated by a high CHO meal or snack, desire for CHO is reduced Need for serotonin substrate may explain why carbohydrate restriction leads to craving of carbohydrates Individuals who are insulin­resistant have more difficulty getting tryptophan into the brain, and thus may crave CHO more strongly Effects of Serotonin, cont. Effects Serotonin appears to have a calming, uplifting effect on mood, but can contribute to drowsiness, clumsiness, & mental slowness Medications which raise serotonin levels in the brain are used to treat depression Application of Dietary “Manipulation” of Serotonin Dietary If a student wants to avoid being drowsy and maximize mental function during a test, probably best not to consume a high CHO, low protein meal or snack before the test. Combo of protein & CHO better. If student tends to get anxious when taking tests, modifying diet to elevate serotonin may help to calm anxiety. Probably best not to go to extremes with CHO consumption, in order to avoid adverse effects on mental function Application, cont. Application, If a person has trouble sleeping, high CHO, low protein snack at bedtime may help to increase drowsiness Lipids and Behavior Lipids Mortality data from subjects participating in cholesterol­lowering studies showed that those who were receiving cholesterol­lowering drugs or dietary treatments were twice as likely as controls to die from suicide or violence. Monkeys fed a diet low in fat & cholesterol had lower brain serotonin & were rated as significantly more aggressive & less social than monkeys fed a high fat diet Lipids & Behavior, cont. Lipids Lower serum cholesterol in human beings has been linked with both suicide and aggression Fish oil was shown to reduce aggression in college students under the stress of final exams. Omega 3 fatty acid supplements (esp. EPA) are showing some effectiveness in the treatment of bipolar disorder in research conducted by Dr. Andrew Stoll at Harvard Lipids and Behavior, cont. Lipids One study (Stevens) found that 40% of children with ADHD had low blood levels of Omega 3 fatty acids – Had symptoms of fatty acid deficiency (excess thirst, increased need to urinate, dry hair & skin) – Significantly greater behavioral problems with more freequent & excessive temper tantrums – Significantly greater learning problems Other Food/Brain Relationships Other People given a snack during a learning task exhibited better recall later than when no snack was given Mice given food immediately after a learning task remembered how to perform the task better than mice fed before the task Possibly associated with survival mechanism – brain remembers behavior that is rewarded with food Supplements for Brain Function? Supplements Gingko biloba has been studied in older subjects with impaired brain function and results showed slight improvement. Effect of most supplements marketed to improve brain function is not proven Many supplements marketed do have high caffeine content, which improves alertness. Caffeine is considered to be a “drug”, due to its known effects. ...
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