The amino acid phenylalanine is the precursor to tyrosine and has been used in numerous studies to successfully treat depression.
Many supplement manufacturers will combine tyrosine and phenylalanine, but vitamin B6 should be added to this combination for better utilization.
This amino acid should be avoided by people who have PKU (phenylketonuria), a genetic defect in the body's ability to process and use phenylalanine. This defect can cause severe retardation. If it is caught early enough, retardation can be avoided with a phenylalanine-free diet. Some researchers believe that many children who are hyperactive or have learning disabilities are suffering from a mild form of PKU. Because there are a small number of women whose phenylalanine levels fluctuate when they are pregnant, this amino acid should be avoided if you are pregnant, just to be on the safe side.
The most common source of phenylalanine these days is the artificial sweetener aspartame (NutraSweet). Every time you use aspartame you get some phenylalanine and aspartic acid. However, it's better to
take phenylalanine in a supplement because we don't know enough about aspartic acid and its side effects, or what it does in combination with phenylalanine.
Phenylalanine has been reported to raise blood pressure, so if you have high blood pressure please monitor it carefully or consult your doctor. Phenylalanine gives some people headaches. A few studies suggest that phenylalanine may promote the growth of cancerous tumors, so if you have cancer this should not be your antidepressant of choice, and please avoid the aspartame! You can take up to 500 mg of phenylalanine three times a day.