Tag Archives: PKU

Phenylalanine amino acid: Importance of PKU Screening in Newborn Babies

In the United States a heel stick test (using a needle prick on the baby’s heel for a small blood sample) is done at the ripe old age of 3 days old to test for Phenylketonuria (PKU) and other disorders. PKU is a metabolic disorder that shows up when the gene is inherited from both parents of the newborn, which is an enzyme deficiency that is needed for proper metabolism of the amino acid phenylalanine.

People with PKU must avoid foods that contain phenylalanine altogether from birth, however, in order to survive since side effects can include pigmentation loss in the skin/eyes/hair, a “mousy” odor, muscles pains and aches, seizures, and mental retardation.

Newborn screening and phenylalanine-restricted diets for PKU patients

Phenylalanine is an essential amino acid that is in foods, including proteins like meats, dairy products, beans, eggs, tofu, nuts, and many others, including aspartame (the sugar substitute in diet soda). An “essential” amino acid means that the body cannot produce this amino acid on its own so it must be gotten from food. Aminos phenylalanine and tyrosine are both associated with PKU and are tested for in all newborn babies at clinics and hospitals.

According to the American Academy of Family Physicians, it is Dr. Richard Koch from the University of Southern California School of Medicine in Los Angeles, California, who promotes that repeat testing should occur in any child that tests positive for PKU. The amino acid phenylalanine in foods should be avoided and a special diet should begin from birth so as to prevent mental retardation.

Koch says, “Occasionally, cases of PKU are missed by newborn screening. Thus, a repeat PKU test should be performed in an infant who exhibits slow development.”

Phenlyketonuria (PKU) is a recessive defect in the enzyme phenylalanine hydroxylase

Koch discusses the enzyme deficiency: “Phenylketonuria (PKU) is caused by an autosomal recessive defect in the enzyme phenylalanine hydroxylase, which is required for converting phenylalanine to tyrosine. (Five percent of natural protein is composed of phenylalanine.)”

PKU is caused by a mutation that is located on chromosome 12, although the specific type of mutation may vary, which results in severity that is variable among those with the PKU disorder. Phenylalanine containing foods should be avoided in all of these cases. Of course, normal people who do not have PKU need phenylalanine and should have a diet consisting of enough proteins to provide this essential amino acid.




L-Phenylalanine Benefts and Dangers

There is an old saying that nothing, in and of itself, is either good or bad. This is true also of the amino acid phenylalanine. What the pros or cons are of taking this amino acid depends on your situation. I will go over some of the dangers as well as the health benefits of this essential amino acid (amino acids are building blocks for protein). “Essential” means that you have to get this amino acid through your diet since your body cannot make it on its own.

Phenylalanine Dangers

The dangers of phenylalanine can include things like drinking sodas that contain artificial sweeteners like aspartame (Nutrasweet, Equal) that contain phenylalanine, but only if you have PKU. PKU is the genetic disorder phenylketonuria, which can cause brain damage or mental retardation or even seizures or death. Phenylalanine is found in protein foods such as meat (beef, chicken, pork, turkey, etc.), fish, eggs, and dairy, and can also be purchased as supplements.

Phenylalanine is not a health concern for healthy people who do not have PKU. However, aspartame, according to the Mayo Clinic, can cause “a rapid increase in the brain levels of phenylalanine” in large doses. They advise to use aspartame-containing products cautiously if you take medications like neuroleptics, monoamine oxidase inhibitors, or medicines that contain levodopa; avoid phenylalanine also if you have tardive dyskinesia, have a sleep disorder, or other mental health condition, including anxiety disorder.

All of that said, what are the benefits of phenylalanine?

L-Phenylalanine Benefits

The different forms include D- phenylalanine, L- phenylalanine, and DL- phenylalanine (50/50) in the forms of phenylalanine supplementation. In fact, all 22 common amino acids are provided by protein foods.

The University of Maryland Medical Center says that the “body changes phenylalanine into tyrosine, another amino acid that’s needed to make proteins, brain chemicals, including L-dopa, epinephrine, and norepinephrine, and thyroid hormones.”

Norepinephrine also affects mood, so phenylalanine is used to help treat depression. People who are deficient in this amino can experience a lack of energy, confusion, memory issues, lack of appetite, decreased alertness, and depression.

The University of Michigan Health System says that the form L-phenylalanine (LPA) can be converted to L-tyrosine, but also into “ L-dopa, norepinephrine, and epinephrine. LPA can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood.”

Other uses for phenylalanine include treating:

Alcohol withdrawal
Chronic pain
Lower back pain
Parkinson’s disease
Rheumatoid arthritis

Please check with your doctor before diagnosing or taking any phenylalanine supplements or making any serious changes to your lifestyle, including diet and protein foods that contain this amino acid.