Phenylalanine and tyrosine
What it is and what it does
- Phenylalanine is one of the nine essential amino acids, along with the others listed by MedlinePlus. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Of the two aromatic amino acids, phenylalanine is essential; tyrosine is made when phenylalanine is broken down. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- Tyrosine is listed as a conditionally essential amino acid: usually not essential, except in times of illness and stress. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- A healthy adult can make tyrosine from phenylalanine, but a young child may not yet have developed the enzyme needed (phenylalanine hydroxylase). (Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. StatPearls [Internet], StatPearls Publishing (NCBI Bookshelf NBK557845; last update April 30, 2024))
- Tyrosine is converted into hormones such as the thyroid hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), and into the pigment melanin. (Lopez MJ, Mohiuddin SS. Biochemistry, Essential Amino Acids. StatPearls [Internet], StatPearls Publishing (NCBI Bookshelf NBK557845; last update April 30, 2024))
- Phenylalanine plays a role in the body's production of melanin, the pigment of skin and hair. (MedlinePlus Medical Encyclopedia: Phenylketonuria (review date 4/8/2025))
- Tyrosine in the diet reduces ('spares') part of the need for phenylalanine. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
Why it matters
- Phenylketonuria (PKU) is a rare inherited condition in which a baby is born unable to break down phenylalanine properly. (MedlinePlus Medical Encyclopedia: Phenylketonuria (review date 4/8/2025))
- Without the enzyme, phenylalanine builds up in the body; this can harm the central nervous system and cause brain damage. (MedlinePlus Medical Encyclopedia: Phenylketonuria (review date 4/8/2025))
- PKU can be detected with a simple blood test. (MedlinePlus Medical Encyclopedia: Phenylketonuria (review date 4/8/2025))
- WHO/FAO/UNU note that the aromatic amino acids (phenylalanine and tyrosine) may be toxic at high concentrations in the body; the body keeps their tissue levels very low. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
General information, not medical advice — for your own needs, ask a doctor or dietitian.
How much is needed
| Who | Amount | What the figure is | Whose figure |
|---|---|---|---|
| Adults | 38 mg per g protein | Recommended amino acid pattern (ICMR-NIN 2020) | ICMR-NIN 2020 (as printed in DGI 2024 Table 8.2) |
| Adults (mean requirement) | 25 mg/kg body weight/day | Average requirement | FAO/WHO/UNU 2007 (not an Indian value) |
| Older children, adolescents and adults | 41 mg per g protein | Scoring pattern for protein quality | FAO 2013 (not an Indian value) |
India’s own figure (ICMR-NIN 2020) comes first. Figures from other bodies are shown only where they help, and say whose they are.
Sources: ICMR-NIN. Dietary Guidelines for Indians 2024; WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935; FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92
In every millet and pseudo-cereal, per 100 g raw
| Grain | Amount | Source |
|---|---|---|
| Phenylalanine | ||
| Kodo millet | 6.27 g per 100 g protein | IFCT A017 |
| Little millet | 6.14 g per 100 g protein | IFCT A016 |
| Ragi (finger millet) | 5.7 g per 100 g protein | IFCT A010 |
| Jowar (sorghum) | 5.1 g per 100 g protein | IFCT A005 |
| Bajra (pearl millet) | 4.82 g per 100 g protein | IFCT A003 |
| Rajgira (amaranth) | 4.75 g per 100 g protein | IFCT A002 |
| Quinoa | 4.35 g per 100 g protein | IFCT A009 |
| Teff | 0.698 g | USDA FDC 169747 |
| Proso millet | 0.58 g | USDA FDC 169702 |
| Kuttu (buckwheat) | 0.52 g | USDA FDC 170286 |
| Tyrosine | ||
| Kodo millet | 3.87 g per 100 g protein | IFCT A017 |
| Jowar (sorghum) | 3.61 g per 100 g protein | IFCT A005 |
| Little millet | 3.43 g per 100 g protein | IFCT A016 |
| Ragi (finger millet) | 3.37 g per 100 g protein | IFCT A010 |
| Rajgira (amaranth) | 3.1 g per 100 g protein | IFCT A002 |
| Bajra (pearl millet) | 2.67 g per 100 g protein | IFCT A003 |
| Quinoa | 1.98 g per 100 g protein | IFCT A009 |
| Teff | 0.458 g | USDA FDC 169747 |
| Proso millet | 0.34 g | USDA FDC 169702 |
| Kuttu (buckwheat) | 0.241 g | USDA FDC 170286 |
Each grain has ONE source, named on its page: IFCT = Indian Food Composition Tables 2017 (ICMR-NIN) with its food code; USDA FDC; FAO WAFCT 2019; NIN 2007 via ICAR-IIMR. Values exactly as printed, not converted — tables differ in method, so compare within a source. Published values for the grain, not a laboratory test of our packs.
Absorption and food
- Phenylalanine is found in foods that contain protein. (MedlinePlus Medical Encyclopedia: Phenylketonuria (review date 4/8/2025))
- ICMR-NIN's model vegetarian diet ('My Plate for the Day') provides 87.9 mg phenylalanine + tyrosine per g of protein, more than the 38 mg/g recommendation. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Compared with the requirement pattern, the aromatic amino acids are present at about 240-320% in milk, soya, potato, rice, maize and wheat proteins, and at 317% in the Indian diet. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)