L-Phenylalanine & Weight Loss

frittata with vegetables
An egg and vegetable omelette. (Image: Olha_Afanasieva/iStock/Getty Images)

The key to weight loss is simple, says the Centers for Disease Control and Prevention: burn more calories than you consume by reducing your intake, exercising more or both. The chemistry underlying the process -- including what compounds stimulate or suppress hunger and why -- is complex, however, and not fully understood. L-phenylalanine, one of the nine essential amino acids your body uses to build proteins, appears to play a role in weight regulation, but more research is needed.

L-Phenylalanine and Cholecystokinin

Cholecystokinin, or CCK, is a hormone produced by cells in the small intestine when food enters the digestive tract, particularly food containing fats or amino acids. L-phenylalanine is one of the amino acids that stimulates CCK release. An article published in "Obesity Reviews" in 2005 reported that the presence of CCK suppresses appetite and may result in reduced caloric intake in the short term. But it's not known whether consuming more L-phenylalanine will result in greater appetite suppression or whether the effect of CCK can be used to promote long-term, sustainable weight loss.

L-Phenylalanine and Dopamine

L-phenylalanine is necessary for the production of the amino acid tyrosine. Tyrosine, in turn, aids with the synthesis of dopamine, a neurotransmitter released when you engage in a pleasurable activity, such as eating your favorite dessert. A "Nutrition & Metabolism" study, published in 2008, reported a link between obesity and dopamine. Overeating or indulging in fattening foods can cause an upsurge in dopamine. When you stop the activity -- go on a diet, for instance -- the drop in dopamine appears to stimulate appetite and result in weight gain. Keeping your dopamine level high might aid weight loss, but studies need to be done with humans, and it's not known if consuming more phenylalanine will help.

How to Increase Your L-Phenylalanine Intake

If you want to increase your L-phenylalanine intake as part of a weight-loss strategy, include plenty of protein-rich foods like beans, legumes, eggs, low- and nonfat dairy, poultry, seafood and lean meat in your diet. Swiss or provolone cheese, nuts like peanuts and almonds, yellowtail fish, toasted sunflower seed kernels, pork and the dark meat of chicken are some of the richest natural sources of phenylalanine. Watch your overall intake -- if you simply add these foods into your diet without keeping your daily calorie consumption under control, you'll gain pounds, not lose them.

Supplementing with L-Phenylalanine

Nonprescription dietary supplements containing D- or DL-phenylalanine aren't regulated by the U.S. Food and Drug Administration. There are few ways to confirm that the supplements aren't contaminated with potentially harmful ingredients or that they contain the amount of the amino acid advertised. In addition, there aren't any studies proving that long-term phenylalanine use is a safe or effective weight-loss method. Phenylalanine supplementation can interfere with the function of drugs like levodopa or anti-psychotic medications. Do not attempt to include phenylalanine in your weight-management strategy until you've talked to your doctor first, especially if you are pregnant or nursing or have a chronic medical condition like kidney or liver disease.

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