A normal dietary intake of phenylalanine is safe for almost everyone, including pregnant women, despite what you may read on the Internet (see
Dangers of Phenylalanine for more information).
However, it is not known if phenylalanine supplementation is safe for pregnant women. There are no reliable studies showing that such supplements are either safe or unsafe for use during pregnancy. It might seem logical to assume that phenylalanine supplements would be perfectly safe for pregnant women, since phenylalanine is an amino acid that is found naturally in many foods. But just because a normal dietary intake through food is safe, it cannot be assumed that using supplements medicinally is equally safe. Perhaps the higher levels could cause problems, or perhaps the phenylalanine in supplements is slightly different from the phenylalanine found in foods. Until more information is available, it is best to wait until after pregnancy to try phenylalanine supplements.
Women with phenylketonuria (PKU) should not take phenylalanine, especially during pregnancy. This could cause severe birth defects and other problems. PKU is a rare genetic condition in which the body does not process phenylalanine normally.
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