The essential amino acid tryptophan synthesizes numerous proteins and other important substances in your body, such as serotonin, a neurotransmitter associated with appetite suppression. Appetite is a desire to eat. Increasing your appetite can lead to overeating, weight gain and obesity, whereas suppressing your appetite can lead to under-eating, weight loss and anorexia. Consult your doctor about tryptophan and appetite.
Tryptophan and Serotonin
Tryptophan is a serotonin precursor. Tryptophan enters the brain from the blood through the blood-brain barrier. In the brain tryptophan is converted to 5 hydroxytryptophan that converts to serotonin. Scientists at McGill University in Montreal, Quebec, Canada published the study "Pharmacology, Biochemistry and Behavior" in April 2002 and reported that alterations in brain tryptophan levels cause changes in brain serotonin synthesis and behavior. A deficiency of brain levels of tryptophan can cause a deficiency of serotonin, which is associated with depression, insomnia and hunger.
Dietary Tryptophan
Diet can affect the availability of tryptophan. Eating a high protein, low carbohydrate meal can reduce the amount of tryptophan that enters your brain, whereas a high carbohydrate, low protein meal can increase the amount of tryptophan that enters the brain. Increasing carbohydrate intake boosts insulin release, which improves the uptake of branched-chain amino acids from the blood, thus elevating the ratio of tryptophan to other amino acids. Scientists at the Massachusetts Institute of Technology in Cambridge report that carbohydrate consumption increases brain serotonin release, whereas protein lacks this effect.
Appetite
The brainstem and hypothalamus control appetite in conjunction with signals from your stomach and fat cells. Scientists at Imperial College London in London, England reported in "Endocrinology and Metabolism Clinics of North America" in December 2010 that the stomach releases hormones after a meal to signal satiety to the brain that initiates meal termination. Cholecystokinin made in the stomach, glucagonlike peptides 1 and 2 made in the small intestine and leptin, made in fat cells, are hormones that cause satiety. However, the brain can override the stomach when palatable food is present, no matter your calorie requirements.
Tryptophan and Hunger
Diet and blood levels of tryptophan influence hunger. A dietary deficiency of tryptophan can lead to reduced blood levels of the amino acid and decreased brain levels of serotonin that can result in increased hunger. Research by scientists at the University of Tubingen in Germany report that the depletion of tryptophan increases hunger.
References
- University of Arizona; The Chemistry of Amino Acids; September 30 2003
- The Center for the Improvement Of Human Functioning International; Proteins / Amino Acids Mar 21 2011
- "Pharmacology, Biochemistry and Behavior"; The Role of Serotonin in Human Mood and Social Interaction. Insight from Altered Tryptophan Levels; Simon Young; Apr 2002
- "Obesity Research"; Brain Serotonin, Carbohydrate-Craving, Obesity and Depression; Richard Wurtman; Nov 1995
- "Endocrinology and Metabolism Clinics of North America"; Appetite and Hedonism: Gut Hormones and the Brain; Katherine Simpson; Dec 2010
- "Neurogastroenterology and Motility"; Acute Tryptophan Depletion Increases Experimental Nausea but Also Induces Hunger in Healthy Female Subjects; N. Rieber, et al.; Jul 2010
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