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Phenylalanine: Fun to say, but is it dangerous?

Doublemint Gum Phenylketonurics Phenylalanine
Phenylketonurics: Contains phenylalanine. This warning can be found on packages for many chewing gums, artificial sweeteners, and carbonated beverages.

If you’re like most people you probably don’t know what this chemical is, let alone how to pronounce it (feen – ill – ala – neen).  Chances are you’ve seen a warning about its presence in a product you’ve purchased, but is there a real danger behind it?  For 1 out of every 15,000 people in the U.S., there is.

I’ve always wondered about this chemical and what exactly it is.  When I was a kid, my older sister and I would see warnings similar to the one in the picture above and we’d laugh at the seemingly carefree name.  PhenyLALAnine.  We were cool kids, if you couldn’t tell.  Since then I’ve read a little about it in anatomy and physiology books, but never really looked into it until I was doing some leisure research on organic chemistry last night (because I’m still that cool).

Turns out phenylalanine is an essential amino acid that is produced naturally in our bodies and it is mainly found in the breast milk of mammals.  It is one of the common amino acids used by biochemists to form proteins and it is sold as a nutritional supplement that acts as a pain-killer and antidepressant.  The body converts phenylalanine into tyrosine (another amino acid), then into dopamine, epinephrine (adrenaline), norepinephrine, and melanin (skin pigment).  Let’s take a quick look at these chemicals to gain a greater appreciation for phenylalanine before moving on further.

Dopamine is a neurotransmitter that has several functions, one of which is playing a role in reward-motivated behavior that involves pleasure-seeking and gratification.  This neurotransmitter triggers our pleasure centers and motivates us to seek rewards.  Cocaine and amphetamine copy the effects of dopamine on the brain, which is what makes them so addictive and why they cause depression when users are going through withdrawal.  In fact, scientists found that not only do people going through depression have lower levels of dopamine in their brains, but that taking a single sip of beer can trigger dopamine release in order to activate our pleasure centers to motivate us to repeat the pleasurable experience in the future.

Epinephrine, or adrenaline, is a hormone released when our bodies go into a “fight-or-flight response.”  It increases heart rate and opens airways, but is also associated with fear and is typically floating through our bloodstream and our brains when we are afraid.  Moreover, recent research suggests adrenaline also enhances our long-term memory — especially with memories involving arousal or fear.

Norepinephrine is a hormone and neurotransmitter that is also released during a fight-or-flight response.  Like epinephrine, norepinephrine increases heart rate.  However, it also affects attention levels, increases blood flow to muscles, and brings more oxygen to the brain.  It also is thought to play a role in learning and decision-making by detecting alterations in patterns:  norepinephrine levels spike during instances of uncertainty and emotional arousal.

Melanin is skin pigment.  The more you have the darker you are.

So what does this mean for phenylalanine?  Is it an ingenious marketing ploy?  In ridiculously high doses, chewing gum with phenylalanine can theoretically relieve pain and make you happy.  Then once converted into dopamine, the “reward-center” of your brain is activated in the same way it is stimulated by cocaine.  And now you’re addicted.  But the buck doesn’t stop there.  Your heart rate increases as some more phenylalanine is converted into norepinephrine and you realize there was an alteration in your life pattern.  A disturbance in the force, if you will.  Just what kind of gum is this?  You take a look at the nifty package labeling and see the name of this magical gum.  Some more phenylalanine converts into epinephrine to give you an adrenaline rush and increase your long-term memory so you’ll be sure to remember  what brand of gum gave you this wonderful minty sensation.  Remaining phenylalanine converts into melanin and now you have a nice bronze or ebony tan going on.  Hell yeah.  Your self-esteem goes up a few points and you can hardly believe there is a gum company out there that wants you to be this happy and this satisfied with its product.  Thanks phenylalanine!

No, that’s not the reason for the warning.  Turns out, the warning is for people with phenylketonuria — a medical condition that inhibits phenylalanine metabolism in the body — not for people with overactive imaginations.

Phenylketonuria (PKU) is a genetic disorder that, when left untreated, can lead to mental retardation, seizures, neurological problems, mood disorders, behavioral problems, and growth deficiencies.  Because PKU is an autosomal recessive trait, both parents must have the gene to pass the disorder onto their offspring.  PKU occurs at a rate of approximately 1 in 15,000 births in the United States.  Turkey has the most frequent cases (1 in 2,600 births) and Finland has the least frequent (less than 1 in 100,000 births).   Infants are typically tested for PKU at birth.  Treatment of this disease involves adhering to a special diet that restricts meat, eggs, nuts, cheese, legumes, bread, corn, and artificial sweeteners that contain aspartame — though most foods have phenylalanine in them.  Amino acids that derive from phenylalanine may be supplemented, including tyrosine, so patients can still receive essential nutrients and synthesize the hormones and neurotransmitters that come from tyrosine (dopamine, epinephrine, norepinephrine, and melanin) though gene therapy may be an option in the future.

It’s an interesting disease.  People who have PKU must avoid phenylalanine but still take in some to continue developing normally.  Doctors try to help them reach an “optimal health range” of phenylalanine within the first 10 years of their lives to help promote healthy development.  If they take in too much phenylalanine, it builds up in their bodies and blocks important amino acids responsible for protein and neurotransmitter synthesis from entering their brains.  This can cause mental retardation in developing individuals and a slew of other problems for all patients.

Imagine if these individuals could no longer synthesize dopamine to feel pleasure, gratification, or motivation.  Couldn’t synthesize serotonin for happiness or epinephrine for adrenaline.  Weren’t aware of their disease and because of their diets, stopped developing mentally at the age of 10 or 15.  These are serious consequences for people with PKU if they don’t monitor their diets or heed those little warnings on packs of gum and artificial sweetener.

So now you know more about phenylalanine than you probably ever cared to know.  It’s an essential amino acid that is important for human development and is the source for many hormones and neurotransmitters that promote healthy brain chemistry.  But for those with PKU, it is a stack of dishes in a continuous balancing act:  too much or too little can lead to disastrous, life-changing results.

Think about that the next time you see this warning somewhere and you’ll be reminded of just how lucky you really are.  I guarantee it will put your life into perspective and make your day that much better.

EDIT:  From Katherine Zeratsky, R.D., L.D. at Mayoclinic.com —

If you don’t have PKU, you probably don’t need to worry about harmful health effects of phenylalanine — with certain important exceptions. Aspartame in large doses can cause a rapid increase in the brain levels of phenylalanine. Because of this, use products with aspartame cautiously if you:

  • Take certain medications, such as monoamine oxidase inhibitors, neuroleptics or medications that contain levodopa
  • Have tardive dyskinesia
  • Have a sleep disorder
  • Have an anxiety disorder or other mental health condition

If you aren’t sure if phenylalanine or aspartame is a concern for you, talk to your doctor.