Though phenylalanine side effects are generally beneficial to the body, in individuals who intake too much or can't properly metabolize it, side effects can be severely negative. In these cases, side effects can include hypertension, seizures and brain damage. As an essential amino acid, phenylalanine’s most apparent and beneficial side effect is its function as a necessary building block for protein; it also may help create chemicals that work to regulate appetite and mood.
In spite of it being a necessary part of a healthy diet, the body doesn’t create phenylalanine naturally. Fortunately, it can be found in a variety of food products, particularly items high in protein, such as beef, poultry, pork and fish. It's also naturally found in milk and bananas as well as a variety of nuts. Other food products have artificially added phenylalanine, such as certain chewing gums and soft drinks that use the sweetener aspartame. There are three major types of phenylalanine, each with different side effects: L-phenylalanine, the amino acid's natural form; D-phenylalanine, the same as L-phenylalanine but made in a lab; and DL-phenylalanine, a mixture of the L and D types.
A deficiency in L-phenylalanine is often evident when one exhibits signs of depression and fatigue. This may be due to the body's use of phenylalanine to produce the amino acid tyrosine, which in turn produces dopamine, norepinephrine and other chemicals that regulate mood and adrenaline. Thus, many believe that one of the most significant phenylalanine side effects is its ability to regulate mood and help combat depression.
Studies have also found that L-phenylalanine may be helpful in the treatment of vitiligo, a condition that causes the skin to depigment, resulting in splotchy patches of white skin. One of the main treatments for vitiligo is UVA radiation. Some studies suggest that topical or oral ingestion of L-phenylalanine enhances the effect of the radiation treatment.
Some researchers also believe that beneficial phenylalanine side effects include alleviating symptoms of Parkinson's disease. Parkinson's disease attacks the central nervous system, negatively impacting an array of motor skills. It’s been proposed that D-phenylalanine improves muscle rigidity, and helps with walking and speech difficulties, thus providing a helpful supplement to the treatment of Parkinson's disease.
Some researchers also suggest that phenylalanine may act as a natural pain killer, or analgesic. As such, it is sometimes use to treat chronic pain, including back pain, migraines and toothaches. It also is sometimes used as a natural appetite suppressant.
DL-phenylalanine is used by some to treat symptoms of premenstrual syndrome, better known as PMS. The science behind treating PMS with this form of phenylalanine is the same as using L-phenylalanine to treat depression. The theory is that DL-phenylalanine spurs on chemical processes within the body to better regulate depression and anxiety.
Phenylalanine side effects can be as damaging as they are often beneficial. One of the most frightening side effects occurs in people who suffer from phenylketonuria (PKU), a disorder in which the afflicted individual is unable to produce the enzyme needed to metabolize phenylalanine. Left untreated, PKU can cause seizures and brain damage. Abnormalities from PKU are so feared that it is standard for most babies to be checked for this disorder within the first few days of life.
Although there is no cure, PKU can be treated with a carefully regulated diet, as well as with close monitoring of phenylalanine blood levels. With such treatment, it’s not uncommon for individuals afflicted with PKU to avoid negative phenylalanine side effects and live normal lives.
It isn’t just people with PKU who can suffer from a diet too rich in phenylalanine; anyone is capable of overdosing, with damaging results. Some children, for example, may experience hypertension as a result of phenylalanine being an ingredient in some medications for Attention Deficit Disorder (ADD).
High doses of the amino acid may also cause nerve damage; phenylalanine has been found in some studies to cause cellular death in nerves. This can be a result of a diet high in aspartame, an artificial sweetener loaded with phenylalanine that's found in many packaged foods, sweeteners and soft drinks. Individuals can also experience headaches, nausea and heartburn as a side effect of overdosing on phenylalanine.