L-Phenylalanine Review

L-Phenylalanine is an amino acid that can act as an appetite suppressant by releasing an intestinal hormone called cholecystokinin. Cholecystokinin (CCK) signal to the brain a feeling of satiation. As food enters the stomach, CCK is naturally released, cluing the body in that the digestive process needs to begin. Because L-Phenylalanine administers the release of CCK, you’ll see it included in many weight loss supplements.

Phenylalanine can be found in any number of healthy foods: soy, sesame seeds, pumpkin seeds, lima beans, fish, bananas, avocados, and almonds, among others. You may be asking yourself then, why a person wouldn’t just eat these foods and not worry about supplementation? The obvious answer is that these foods aren’t light on the calories (except for the lima beans and fish, depending on how the fish is prepared). Supplementation would give you the appetite suppressing benefits without the calories.

L-Phenylalanine, along with L-Tyrosine (see my tyrosine review here) and methonine, helps the body produce adrenaline. Purportedly, it also elevates your mood (which can be a good thing when finding that extra drive while working out).  What we care about most though, is its ability to suppress the appetite.

Research into L-Phenylalanine’s Appetite Suppressing Ability

One study done over 30 years ago involved decreasing the food intake of rhesus monkeys, then offering them food after injecting them with l-phenylalanine.  According to the study, the monkeys demonstrated characteristics of suppressed appetite1.  View the abstract.

There isn’t a lot of other research out there that involves l-phenylalanine’s appetite suppressing ability — mainly because it’s accepted as proven.  It does certainly administer to the release of Cholecystokinin, and CCK does certainly release a signal to the brain that the body is full.

L-Phenylalanine gets the thumbs up as far as diet pill ingredients go.

  1. Gibbs J; Falasco JD; McHugh R. Cholecystokinin-decreased food intake in rhesus monkeys. Am J Physiol, 1976 Jan, 230:1, 15-18. [↩]