What Is the Scientific Evidence for Phenylalanine?
A pair of double-blind comparative studies found that D- or DL-phenylalanine may be as effective as the antidepressant drug imipramine, and possibly work more quickly. The larger of the two studies compared the effectiveness of D-phenylalanine at 100 mg daily against the same daily dose of imipramine. 15 Sixty people with depression were randomly assigned to take either imipramine or D-phenylalanine for 30 days. The results in both groups were statistically equivalent, meaning that phenylalanine was about as effective as imipramine. D-phenylalanine worked more rapidly, however, producing significant improvement in only 15 days. Like most antidepressant drugs, imipramine required several weeks to take effect. The other double-blind study followed 27 people, half of whom received DL-phenylalanine (150 to 200 mg daily) and the other half imipramine (100 to 150 mg daily). 16 When they were reevaluated after 30 days, both groups had improved by a statistically equal amount. L-phenylalanine
