Phenylalanine in Foods and Drinks: What You Need to Know

Table of ContentsView AllTable of ContentsFoods High In PhenylalanineHealth BenefitsSafetyOptimizing Amino Acids

Table of ContentsView All

View All

Table of Contents

Foods High In Phenylalanine

Health Benefits

Safety

Optimizing Amino Acids

Phenylalanineis an amino acid, a compound your body uses to make proteins. It’s an essential amino acid, meaning you must get it from your diet because the human body can’t produce it.

When you consume phenylalanine, your body converts it into tyrosine, another amino acid, which is then used to produce important brain chemicals like dopamine, norepinephrine, and epinephrine.

Phenylalanine is found in manyhigh-protein foods, such as animal proteins, and some plant-based sources like soy products andlegumes(e.g., beans, peanuts, lentils).

Here’s where you can find it:

As an Added Ingredient

It is often found in “light” or “diet” beverages and foods containingaspartameas an artificial sweetening agent. Aspartame is made of phenylalanine and anotheramino acidcalled aspartic acid.

Otherwise, manufacturers may intentionally add it to certain protein powders, which often contain additional amino acids, including phenylalanine, to enhance protein content. The best way to know whether a protein powder or other protein-enhanced product (like a sports snack bar) contains phenylalanine is to read the ingredients label.

Health Benefits of Phenylalanine Supplements

Before trying a phenylalanine supplement or any supplement, speak with a healthcare provider or registered dietitian to see if it’s safe and appropriate for you.

Phenylketonuria: Risks and Safety

Phenylalanine is considered safe when consumed through a regular balanced diet for most healthy people, meaning you probably don’t need to boost or track your phenylalanine intake.

However, people who havephenylketonuria(PKU) have to be cautious with how much they’re getting. PKU is a rare inherited genetic disorder that affects how the body processes phenylalanine.

People with PKU have a deficient or nonfunctional phenylalanine hydroxylase enzyme, which converts it into compounds needed to make brain chemicals and regulate the amounts of amino acids in the body. Without this enzyme, phenylalanine builds up in the body and can become toxic.

If someone with PKU has too much phenylalanine in their body, it can be toxic to the brain. If not identified and appropriately treated, it can cause:

Fortunately, PKU is usually diagnosed through routine newborn screening tests, which are done within a few days of birth to check for high levels of phenylalanine in the blood. As with other health conditions, earlier detection of PKU is better.

The primary treatment for PKU includes a lifelong diet that is strictly low in phenylalanine. Alow-phenylalanine dietavoids high-protein foods like meat, dairy, nuts, and certain grains. Additionally, products containing aspartame must carry a warning for people with PKU.

People with PKU must monitor their phenylalanine levels with regular blood tests and adjust their diet accordingly. Sometimes, they may require tyrosine supplements since the amount of this amino acid may be low without phenylalanine.

How to Optimize Amino Acid Production

Eating a dietincorporating adequate proteinis the best way to ensure you get all the amino acids you need. While you may have heard that you should combine certain protein sources simultaneously to ensure you get all the amino acids you need, this is a misconception, and there’s no magic approach.

Some great sources of protein include:

Summary

Phenylalanine is an essential amino acid that most people get more than enough of through protein sources in their everyday diets, whether they eat mostly animal-derived, plant-based, or a mix of both. If you have PKU, it’s important to be aware of your phenylalanine intake and monitor your levels with the help of a healthcare provider.

Most people do not need to think twice about how much phenylalanine they’re getting, as the body uses what it needs to make proteins and brain chemicals and eliminates the rest.

13 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Bose S, Mandal S, Khan R, Maji HS, Ashique S.Current landscape on development of phenylalanine and toxicity of its metabolites - A review.Curr Drug Saf. 2024;19(2):208-217. doi:10.2174/1574886318666230331112800MedlinePlus.PAH gene.MacDonald A, van Wegberg AMJ, Ahring K, et al.PKU dietary handbook to accompany PKU guidelines.Orphanet J Rare Dis. 2020;15(1):171. 2020. doi:10.1186/s13023-020-01391-yAnjum I, Jaffery SS, Fayyaz M, Wajid A, Ans AH.Sugar beverages and dietary sodas impact on brain health: a mini literature review.Cureus. 2018;10(6):e2756. doi:10.7759/cureus.2756Lakhan SE, Vieira KF.Nutritional therapies for mental disorders.Nutr J. 2008;7:2. doi:10.1186/1475-2891-7-2Perna S, Alalwan TA, Al-Thawadi S, et al.Evidence-based role of nutrients and antioxidants for chronic pain management in musculoskeletal frailty and sarcopenia in aging.Geriatrics (Basel). 2020;5(1):16. doi:10.3390/geriatrics5010016Gianfaldoni S, Tchernev G, Lotti J, et al.Unconventional treatments for vitiligo: are they (un)satisfactory?Open Access Maced J Med Sci. 2018;6(1):170-175. doi:10.3889/oamjms.2018.038Church DD, Hirsch KR, Park S, et al.Essential amino acids and protein synthesis: Insights into maximizing the muscle and whole-body response to feeding.Nutrients. 2020;12(12):3717. doi:10.3390/nu12123717Romani C, Palermo L, MacDonald A, Limback E, Hall SK, Geberhiwot T.The impact of phenylalanine levels on cognitive outcomes in adults with phenylketonuria: effects across tasks and developmental stages.Neuropsychology. 2017;31(3):242-254. doi:10.1037/neu0000336Flydal MI, Martinez A.Phenylalanine hydroxylase: function, structure, and regulation.IUBMB Life. 2013;65(4):341-349. doi:10.1002/iub.1150Pilotto A, Zipser CM, Leks E, et al.Phenylalanine effects on brain function in adult phenylketonuria.Neurology. 2021;96(3):e399-e411. doi:10.1212/WNL.0000000000011088Marsh KA, Munn EA, Baines SK.Protein and vegetarian diets.Med J Aust. 2013;199(S4):S7-S10. doi:10.5694/mja11.11492Harvard Health Publishing.High-protein foods: The best protein sources to include in a healthy diet.

13 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Bose S, Mandal S, Khan R, Maji HS, Ashique S.Current landscape on development of phenylalanine and toxicity of its metabolites - A review.Curr Drug Saf. 2024;19(2):208-217. doi:10.2174/1574886318666230331112800MedlinePlus.PAH gene.MacDonald A, van Wegberg AMJ, Ahring K, et al.PKU dietary handbook to accompany PKU guidelines.Orphanet J Rare Dis. 2020;15(1):171. 2020. doi:10.1186/s13023-020-01391-yAnjum I, Jaffery SS, Fayyaz M, Wajid A, Ans AH.Sugar beverages and dietary sodas impact on brain health: a mini literature review.Cureus. 2018;10(6):e2756. doi:10.7759/cureus.2756Lakhan SE, Vieira KF.Nutritional therapies for mental disorders.Nutr J. 2008;7:2. doi:10.1186/1475-2891-7-2Perna S, Alalwan TA, Al-Thawadi S, et al.Evidence-based role of nutrients and antioxidants for chronic pain management in musculoskeletal frailty and sarcopenia in aging.Geriatrics (Basel). 2020;5(1):16. doi:10.3390/geriatrics5010016Gianfaldoni S, Tchernev G, Lotti J, et al.Unconventional treatments for vitiligo: are they (un)satisfactory?Open Access Maced J Med Sci. 2018;6(1):170-175. doi:10.3889/oamjms.2018.038Church DD, Hirsch KR, Park S, et al.Essential amino acids and protein synthesis: Insights into maximizing the muscle and whole-body response to feeding.Nutrients. 2020;12(12):3717. doi:10.3390/nu12123717Romani C, Palermo L, MacDonald A, Limback E, Hall SK, Geberhiwot T.The impact of phenylalanine levels on cognitive outcomes in adults with phenylketonuria: effects across tasks and developmental stages.Neuropsychology. 2017;31(3):242-254. doi:10.1037/neu0000336Flydal MI, Martinez A.Phenylalanine hydroxylase: function, structure, and regulation.IUBMB Life. 2013;65(4):341-349. doi:10.1002/iub.1150Pilotto A, Zipser CM, Leks E, et al.Phenylalanine effects on brain function in adult phenylketonuria.Neurology. 2021;96(3):e399-e411. doi:10.1212/WNL.0000000000011088Marsh KA, Munn EA, Baines SK.Protein and vegetarian diets.Med J Aust. 2013;199(S4):S7-S10. doi:10.5694/mja11.11492Harvard Health Publishing.High-protein foods: The best protein sources to include in a healthy diet.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Bose S, Mandal S, Khan R, Maji HS, Ashique S.Current landscape on development of phenylalanine and toxicity of its metabolites - A review.Curr Drug Saf. 2024;19(2):208-217. doi:10.2174/1574886318666230331112800MedlinePlus.PAH gene.MacDonald A, van Wegberg AMJ, Ahring K, et al.PKU dietary handbook to accompany PKU guidelines.Orphanet J Rare Dis. 2020;15(1):171. 2020. doi:10.1186/s13023-020-01391-yAnjum I, Jaffery SS, Fayyaz M, Wajid A, Ans AH.Sugar beverages and dietary sodas impact on brain health: a mini literature review.Cureus. 2018;10(6):e2756. doi:10.7759/cureus.2756Lakhan SE, Vieira KF.Nutritional therapies for mental disorders.Nutr J. 2008;7:2. doi:10.1186/1475-2891-7-2Perna S, Alalwan TA, Al-Thawadi S, et al.Evidence-based role of nutrients and antioxidants for chronic pain management in musculoskeletal frailty and sarcopenia in aging.Geriatrics (Basel). 2020;5(1):16. doi:10.3390/geriatrics5010016Gianfaldoni S, Tchernev G, Lotti J, et al.Unconventional treatments for vitiligo: are they (un)satisfactory?Open Access Maced J Med Sci. 2018;6(1):170-175. doi:10.3889/oamjms.2018.038Church DD, Hirsch KR, Park S, et al.Essential amino acids and protein synthesis: Insights into maximizing the muscle and whole-body response to feeding.Nutrients. 2020;12(12):3717. doi:10.3390/nu12123717Romani C, Palermo L, MacDonald A, Limback E, Hall SK, Geberhiwot T.The impact of phenylalanine levels on cognitive outcomes in adults with phenylketonuria: effects across tasks and developmental stages.Neuropsychology. 2017;31(3):242-254. doi:10.1037/neu0000336Flydal MI, Martinez A.Phenylalanine hydroxylase: function, structure, and regulation.IUBMB Life. 2013;65(4):341-349. doi:10.1002/iub.1150Pilotto A, Zipser CM, Leks E, et al.Phenylalanine effects on brain function in adult phenylketonuria.Neurology. 2021;96(3):e399-e411. doi:10.1212/WNL.0000000000011088Marsh KA, Munn EA, Baines SK.Protein and vegetarian diets.Med J Aust. 2013;199(S4):S7-S10. doi:10.5694/mja11.11492Harvard Health Publishing.High-protein foods: The best protein sources to include in a healthy diet.

Bose S, Mandal S, Khan R, Maji HS, Ashique S.Current landscape on development of phenylalanine and toxicity of its metabolites - A review.Curr Drug Saf. 2024;19(2):208-217. doi:10.2174/1574886318666230331112800

MedlinePlus.PAH gene.

MacDonald A, van Wegberg AMJ, Ahring K, et al.PKU dietary handbook to accompany PKU guidelines.Orphanet J Rare Dis. 2020;15(1):171. 2020. doi:10.1186/s13023-020-01391-y

Anjum I, Jaffery SS, Fayyaz M, Wajid A, Ans AH.Sugar beverages and dietary sodas impact on brain health: a mini literature review.Cureus. 2018;10(6):e2756. doi:10.7759/cureus.2756

Lakhan SE, Vieira KF.Nutritional therapies for mental disorders.Nutr J. 2008;7:2. doi:10.1186/1475-2891-7-2

Perna S, Alalwan TA, Al-Thawadi S, et al.Evidence-based role of nutrients and antioxidants for chronic pain management in musculoskeletal frailty and sarcopenia in aging.Geriatrics (Basel). 2020;5(1):16. doi:10.3390/geriatrics5010016

Gianfaldoni S, Tchernev G, Lotti J, et al.Unconventional treatments for vitiligo: are they (un)satisfactory?Open Access Maced J Med Sci. 2018;6(1):170-175. doi:10.3889/oamjms.2018.038

Church DD, Hirsch KR, Park S, et al.Essential amino acids and protein synthesis: Insights into maximizing the muscle and whole-body response to feeding.Nutrients. 2020;12(12):3717. doi:10.3390/nu12123717

Romani C, Palermo L, MacDonald A, Limback E, Hall SK, Geberhiwot T.The impact of phenylalanine levels on cognitive outcomes in adults with phenylketonuria: effects across tasks and developmental stages.Neuropsychology. 2017;31(3):242-254. doi:10.1037/neu0000336

Flydal MI, Martinez A.Phenylalanine hydroxylase: function, structure, and regulation.IUBMB Life. 2013;65(4):341-349. doi:10.1002/iub.1150

Pilotto A, Zipser CM, Leks E, et al.Phenylalanine effects on brain function in adult phenylketonuria.Neurology. 2021;96(3):e399-e411. doi:10.1212/WNL.0000000000011088

Marsh KA, Munn EA, Baines SK.Protein and vegetarian diets.Med J Aust. 2013;199(S4):S7-S10. doi:10.5694/mja11.11492

Harvard Health Publishing.High-protein foods: The best protein sources to include in a healthy diet.

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