What is Phenylalanine?
This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Phenylalanine is an essential aromatic amino acid that plays a crucial role in various physiological processes. It is a precursor for several important biomolecules and is vital for normal growth and development. This article explores the significance of phenylalanine, its dietary requirements, and its impact on health. Other names include: 2-amino-3-phenyl-propanoic acid, Acide Alpha-aminohydrocinnamique, Acide Isovalérique de Phénylalanine, Alpha-aminohydrocinnamic Acid, Beta-phenyl-alanine, Bêta-phenyl-alanine, DLPA, D-Phenylalanine, D-Phénylalanine, DL-Phenylalanine, DL-Phénylalanine, D,L-Phenylalanine, D,L-Phénylalanine, Fenilalanina, L-Phenylalanine, L-Phénylalanine, Phenylalanine Ethyl Ester HCl, Phenylalanine Isovaleric Acid, Phenylalanine Methyl Ester HCl.
Phenylalanine Dietary Requirements
Phenylalanine is essential for protein synthesis and must be obtained through the diet. The dietary requirements for phenylalanine vary across different age groups and physiological conditions.
Elderly Adults
A study determined that the phenylalanine requirement for elderly adults is similar to that of young adults. The mean requirement was found to be 9.03 mg/kg/day, with an upper 95% confidence interval of 15.9 mg/kg/day, suggesting that the higher protein needs of the elderly are not driven by an increased requirement for phenylalanine1.
Neonates
For neonates, especially those who are preterm, the phenylalanine requirement is higher. Term neonates require a minimum of 58 mg/kg/day, while preterm neonates need about 80 mg/kg/day. These requirements are crucial for optimal growth and development2.
Healthy Adults
In healthy Indian adults, the phenylalanine requirement was estimated to be around 38 mg/kg/day in the absence of tyrosine intake. This finding aligns with the requirements observed in Western adults7.
Physiological Roles of Phenylalanine
Phenylalanine is not only important for protein synthesis but also plays a role in the synthesis of other critical molecules.
Protein Synthesis and Tyrosine Conversion
Phenylalanine can be hydroxylated to form tyrosine, another essential amino acid. This conversion is vital for the synthesis of neurotransmitters such as dopamine, norepinephrine, and epinephrine, which are crucial for brain function and mood regulation2.
Impact on Cognitive Function
In patients with phenylketonuria (PKU), a condition where phenylalanine cannot be properly metabolized, maintaining appropriate phenylalanine levels is critical. Elevated phenylalanine levels can impact cognitive function and brain structure. A study on adults with early-treated PKU showed that temporarily elevated phenylalanine levels could influence cognitive performance and cerebral parameters3.
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Health Implications of Phenylalanine
Phenylalanine has several health implications, particularly in metabolic and gastrointestinal functions.
Appetite Regulation and Glycemic Control
Phenylalanine stimulates the release of cholecystokinin (CCK) and peptide-YY (PYY), hormones that regulate appetite and energy intake. It also influences glycemic control by stimulating insulin and glucagon release, although it does not affect gastric emptying4.
Exercise and Fat Oxidation
Supplementation with phenylalanine before exercise has been shown to increase fat oxidation. This effect is likely due to the stimulation of glucagon secretion, which promotes fat mobilization during physical activity8.
Pancreatic Development
In milk-fed Holstein calves, phenylalanine supplementation influenced pancreatic development and enzyme activity. It increased the concentration of plasma insulin and cholecystokinin, which are important for digestive processes6.
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Adverse Effects of Phenylalanine
Neuropsychological and Mood Effects
High phenylalanine levels can impair sustained attention and negatively affect mood in adults with PKU1 10.
Bone Health
Elevated plasma phenylalanine concentrations may adversely affect bone status, leading to reduced femur weight and length, and potentially higher bone turnover in PKU mice3.
Body Weight and Food Consumption
High dietary intake of phenylalanine can lead to reduced body weight and food consumption, indicating mild toxicity at higher doses4.
Gastrointestinal and Hormonal Effects
Phenylalanine stimulates the release of gastrointestinal hormones like cholecystokinin (CCK) and peptide-YY (PYY), which can suppress energy intake and affect glycaemic responses2 6 9.
High doses of phenylalanine can cause nausea, which may influence food intake6.
Metabolic and Glucoregulatory Effects
Phenylalanine can stimulate insulin and glucagon release, affecting blood glucose levels2 7.
Mortality and Organ Weight in Animals
In broilers, phenylalanine supplementation in the presence of ochratoxin A (OA) reduced mortality and affected relative organ weights, indicating potential protective effects against OA toxicity8.
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How has Phenylalanine Improved Patient Outcomes?
Breast Cancer Treatment
L-phenylalanine mustard (L-PAM) as an adjuvant to mastectomy significantly improves disease-free survival in premenopausal breast cancer patients, particularly those under 49 years old and those with fewer positive axillary nodes1 3.
Phenylketonuria (PKU) Management
Phenylalanine-free amino acid supplementation in untreated PKU patients improves concentration, awareness, and reduces self-injury, leading to better adaptive behavior2.
Sapropterin (BH4), a synthetic form of tetrahydrobiopterin, significantly reduces blood phenylalanine levels in PKU patients, potentially allowing for less restrictive diets6 8.
Elevated phenylalanine levels negatively impact mood and sustained attention in adults with PKU, suggesting the importance of maintaining a Phe-restricted diet10.
Multiple Sclerosis
Combination therapy with L-phenylalanine, lofepramine, and vitamin B-12 shows a small but significant improvement in disability scores in multiple sclerosis patients4.
Attention Deficit Disorder
DL-phenylalanine shows initial improvement in mood and mood lability in adults with attention deficit disorder, though benefits are not sustained long-term7.
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Phenylalanine Mechanisms of Action
Stimulation of Satiety Hormones and Appetite Regulation
Phenylalanine stimulates the release of cholecystokinin (CCK) and peptide-YY (PYY), which are hormones involved in promoting satiety and reducing energy intake1 7.
The suppression of energy intake by phenylalanine is correlated with the stimulation of CCK and PYY1 7.
Glucoregulatory Effects
Phenylalanine increases the secretion of insulin and glucagon, which are key hormones in glucose metabolism1 2.
It reduces overall and peak plasma glucose levels in response to a mixed-nutrient drink, indicating a role in blood glucose regulation1.
Fat Oxidation During Exercise
Phenylalanine supplementation before exercise increases plasma glycerol and glucagon levels, promoting fat oxidation2.
Pancreatic Development and Enzyme Activity
In animal studies, phenylalanine supplementation increases plasma insulin and cholecystokinin levels, and affects pancreatic DNA concentration and trypsin gene expression3.
Neurological and Cognitive Effects
Elevated phenylalanine levels can influence cognitive performance and brain function, particularly in individuals with phenylketonuria (PKU)4.
Phenylalanine may activate the noradrenergic locus coeruleus/lateral tegmentum (LC/LT) system, potentially affecting brain and spinal cord function5.
Competitive Transport Across the Blood-Brain Barrier
Phenylalanine competes with other large neutral amino acids (LNAA) for transport across the blood-brain barrier, which can be leveraged to lower brain phenylalanine levels in PKU treatment6.
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Common Complaints Associated with Phenylalanine Use
Mood and Cognitive Function
High plasma Phe levels negatively impact mood and sustained attention in adults with PKU1.
Discontinuation of a Phe-restricted diet in PKU patients is associated with increased rates of mental disorders and lower intellectual and achievement test scores2.
Medical and Behavioral Problems
Patients who do not adhere to a Phe-restricted diet report higher incidences of eczema, asthma, headaches, hyperactivity, and hypoactivity2.
Gastrointestinal Issues
Adverse events related to Phe use, particularly in the context of engineered bacterial treatments, are mostly gastrointestinal and of mild to moderate severity3.
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Disclaimer
The content presented in this blog is generated by Consensus, an AI-powered academic search engine, and is based on publicly available scientific literature. While every effort is made to provide accurate, up-to-date, and well-researched information, the content is intended for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding medical conditions, treatments, or medications. The AI system’s analysis may not cover all perspectives, emerging research, or individual cases, and it is not a substitute for professional expertise. Neither the blog publisher nor the developers of the AI-powered search engine are responsible for any actions taken based on the information provided in this content. Use of this information is at your own risk. Citations to the original scientific studies are included for reference, but these studies should be reviewed in full and interpreted with the guidance of a healthcare or research professional.
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