... copy-and-pasted from... from... www.healthline.com/nutrition/phenylalanine#benefits

Benefits of phenylalanine Several studies have examined how phenylalanine might benefit the treatment of certain medical conditions. Some research indicates that taking phenylalanine supplements alongside ultraviolet (UV) light treatment may improve skin pigmentation in individuals with vitiligo, a skin condition that causes loss of skin pigment (13Trusted Source, 14Trusted Source, 15Trusted Source). Phenylalanine can also be used to produce dopamine, a molecule that plays a key role in mental health and depression (2, 10Trusted Source). In a small, older study from 1977 including 12 people with depression, two-thirds of the participants experienced improved symptoms after taking a mixture of the D- and L-forms of the amino acid (16). Newer studies have similarly found that low levels of phenylalanine could be linked to major depressive disorder (11Trusted Source, 12Trusted Source). On the other hand, other older research shows no clear benefits. Ultimately, because there’s limited recent research available on the effects of phenylalanine on depression, more high quality studies are needed (17Trusted Source, 18Trusted Source, 19Trusted Source). In addition to vitiligo and depression, phenylalanine has been studied for potential effects on: Pain. Some older studies have found that D-phenylalanine might relieve pain, but overall, research has turned up mixed results (1, 20Trusted Source, 21Trusted Source, 22Trusted Source). Alcohol withdrawal. According to a 2011 study, using a supplement that contained D-phenylalanine along with other amino acids could help alleviate symptoms of alcohol withdrawal (23Trusted Source). Parkinson’s disease. An older study suggests that phenylalanine may support Parkinson’s disease treatment, but more research is needed. Although inconclusive, tyrosine has also been studied for its effects on brain function and Parkinson’s (24Trusted Source, 25Trusted Source, 26Trusted Source). ADHD. Currently, research does not indicate that this amino acid has any benefits for the treatment of attention deficit hyperactivity disorder (ADHD) (27Trusted Source). SUMMARY Phenylalanine may improve the skin disorder vitiligo when combined with UV treatment. At this time, studies do not support the use of this amino acid to treat other conditions. Dangers and side effects Phenylalanine is found in many protein-containing foods and considered to be generally recognized as safe by the Food and Drug Administration (FDA) (28). The amount found naturally in foods likely doesn’t pose a risk for healthy individuals. What’s more, few or no side effects are generally observed at supplement doses up to 12 grams per day (2, Trusted Source15Trusted Source, 29Trusted Source). Nevertheless, it’s best to use phenylalanine only as directed and check with your doctor before adding any supplements to your routine. People taking medications for schizophrenia should avoid using phenylalanine, as it could worsen symptoms of tardive dyskinesia, a condition characterized by involuntary, repetitive movements (30Trusted SourceTrusted Source, 31Trusted Source). Those who are pregnant or breastfeeding should also avoid taking phenylalanine supplements, as there’s limited research on their safety and potential long-term effects. Furthermore, those with phenylketonuria (PKU) should monitor their intake of the amino acid carefully. This disorder impairs the body’s ability to metabolize phenylalanine, which can lead to high levels in the blood (32Trusted Source). Dangerously high blood concentrations of phenylalanine can cause severe brain damage, delayed growth, intellectual disability, and problems with the transport of other amino acids to the brain (5, 33Trusted Source, 34Trusted Source). PKU is also associated with several other disorders, including epilepsy, overactive reflexes, and neurological issues like tics or tremors. Due to the seriousness of this disorder, newborns are generally screened for it soon after birth (35Trusted Source). Individuals with PKU are placed on a special low protein diet to limit their intake of phenylalanine, which is generally maintained for life (5). SUMMARY For healthy adults, phenylalanine is considered safe in the quantities found naturally in foods. However, individuals with phenylketonuria (PKU) cannot metabolize it and must minimize their intake to prevent adverse health effects. Foods high in phenylalanine Many high protein plant and animal foods contain phenylalanine, including meat, fish, poultry, and legumes. It’s also found in aspartame, an artificial sweetener that’s often added to diet soda and many sugar-free foods (36Trusted Source). Here are some of the top food sources of phenylalanine (4Trusted Source): Meat: beef, pork, lamb, venison Poultry: chicken, turkey, duck, goose Seafood: salmon, trout, tuna, mackerel, shrimp, lobster Eggs: whole eggs, egg whites Dairy: milk, cheese, yogurt Nuts: almonds, pistachios, macadamia nuts, cashews, walnuts Seeds: pumpkin seeds, squash seeds, hemp seeds, sunflower seeds Nut butters: peanut butter, almond butter, cashew butter Legumes: lentils, chickpeas, black beans, kidney beans Whole grains: quinoa, oats, rye, barley, wheat Soy products: soybeans, tofu, tempeh, edamame, protein supplements Diet products: diet soda and sugar-free ice cream, gum, candies, and flavored yogurts made with aspartame Generally, you don’t need to select foods based on their phenylalanine content. Instead, eating a variety of protein-rich foods throughout the day will provide you with all the phenylalanine you need, along with other essential amino acids and nutrients. SUMMARY Many foods, including soy products, eggs, seafood, and meats, contain phenylalanine. Eating a variety of protein-rich foods throughout the day will provide you with the amino acids your body needs, including phenylalanine. The bottom line Phenylalanine is an essential amino acid found in both plant and animal foods. It may benefit the skin disorder vitiligo, but research on its effects on depression, pain, and other conditions is limited. While it’s generally considered safe for healthy individuals, it’s important that those with phenylketonuria (PKU) keep their intake low to avoid potentially dangerous side effects. If you notice any negative side effects after taking a phenylalanine supplement or eating high protein foods, talk with your doctor. They can test your amino acid blood levels and help determine the best course of treatment for you.