Phenylalanine: role in the body, benefits and dangers

Phenylalanine: role in the body, benefits and dangers

Phenylalanine is an amino acid essential for the proper functioning of the body. The body does not produce it, its intake is therefore exogenous (food, food supplements). What is the role of phenylalanine? What foods contain phenylalanine? When to use food supplements? The answers of Elodie Picard, micronutritionist dietician.

What is phenylalanine?

Phenylalanine is a amino acid essential (or essential amino acid), this means that it cannot be manufactured by the body. “Phenylalanine is essential for the synthesis of proteins, amino acids and hormones., indicates Elodie Picard. Our intake of phenylalanine is exogenous, it comes from our diet. In case of deficiency, it is also possible to take food supplements enriched with phenylalanine.

Phenylalanine is a precursor of tyrosine

Once ingested, phenylalanine is converted into tyrosine in the body. “Tyrosine is an amino acid that the body knows how to produce, unlike phenylalanine. It is a precursor of phenylalanine,” explains the micronutritionist dietitian.

Tyrosine occurs at several levels in the body. It is necessary for the synthesis of neurotransmitters, melanin (dark pigment of the skin and hair),thyroid hormones and the regulation of appetite.

Phenylalanine: what is the role of this amino acid?

As we have seen, phenylalanine is necessary for the production of tyrosine. Talking about the roles of phenylalanine in the body is basically explaining what tyrosine is used for.

Tyrosine is essential for the normal synthesis ofadrenalinefrom norepinephrine and some dopamine. These chemicals are neurotransmitters, they are secreted by certain neurons to transmit nerve impulses to other cells. “These neurotransmitters are involved in pleasure, energy, desire, motivation, attention and concentration.points out the micronutrition specialist.

Tyrosine is also necessary for the synthesis of melanin, a dark biological pigment that protects us from the harmful effects of UV rays.

Tyrosine is also an “appetite suppressant” substance. “It boosts the secretion of cholecystokinin, a hormone of the small intestine which regulates appetite and will allow satiety.explains Elodie Picard.

Finally, tyrosine is involved in the production of thyroid hormones including thyroxine and triiodothyronine. Thyroid hormones affect many vital functions of the body, such as heart rate, the rate at which calories are burned, growth, heat production, fertility, digestion… “They also play a role in mood”, points out the micronutritionist dietitian.

Where to find phenylalanine? What food contains phenylalanine?

Phenylalanine is present in significant quantities in:

  • Certain meats such as turkey, poultry, veal liver and game;
  • Oilseeds, particularly nuts;
  • Legumes (lentils, chickpeas, etc.);
  • Certain cheeses, notably Parmesan;
  • Mung beans.

It is also found, in smaller quantities, in eggs, fish and spirulina.

Phenylalanine and Coca Zero: what are the links?

Coke Zero contains aspartame, a sweetener rich in phenylalanine. Aspartame is also present in other low-sugar products (yogurts, desserts, chewing gum, etc.). Low-fat products that contain aspartame are indeed a good source of phenylalanine. But be careful, they should be consumed in moderation because aspartame is a synthetic sweetener which is the subject of controversy regarding its health risk. “It contains aspartic acid, suspected of increasing the risk of cancer”warns Elodie Picard.

When to take food supplements based on phenylalanine?

Characteristic symptoms of tyrosine deficiency

Food supplements can be useful in cases of tyrosine deficiency. “This can result in a chronic fatigue, memory and concentration problems, mild depressive disorders, emotional disorders, etc. To suspect a tyrosine deficiency, these symptoms must have lasted for several months”, explains the dietitian.

Food supplements enriched with phenylalanine can quickly correct a deficiency. But this is a temporary solution. For Elodie Picard, food must be sufficient, in the long term, to cover our phenylalanine needs. “My role is above all to readjust the diet of my patients so that they feel better in their body and in their mind”.

A course of phenylalanine generally lasts two months. The dose will depend on the patient.

Associate phenylalanine with other molecules

“When I prescribe phenylalanine to my patients, I advise them to combine it with other molecules to benefit from their synergy of action”, indicates Elodie Picard. Thus, phenylalanine can be associated with B group vitamins, magnesium and omega 3 DHA. Just like phenylalanine, these molecules have a beneficial effect on the brain.

Contraindications to phenylalanine supplements

Food supplements based on phenylalanine are not recommended:

  • pregnant or breastfeeding women;
  • to people with cardiac pathologies;
  • to people suffering from Parkinson’s disease (their treatments already act on dopaminergic neurons, there is a risk of interaction).
  • to people taking antidepressants (risk of interactions).

Excess phenylalanine in the body: what is the danger?

In healthy people, excess phenylalanine is not dangerous for health. “The body transforms it into tyrosine and excess tyrosine is not harmful to the body.reassures the micro-nutrition specialist.

On the other hand, excess phenylalanine is dangerous for people with phenylketonuria. This rare genetic disease (1 in 16,000 newborns in Europe) prevents people who suffer from it from assimilating phenylalanine.

NO to diets, YES to WW!

What are the consequences of phenylketonuria?

If left untreated, excess phenylalanine causes toxicity to neurons, which impairs brain development. “In these people, phenylalanine, present in excess, can attack myelin, the sheath that protects the nerves”points out the dietitian.

Screening for phenylketonuria has been systematic in Europe since 1972. It is done at birth, by measuring phenylalanine from a dried drop of blood (Guthrie test).

Treatment is mainly based on a diet low in phenylalanine. Patients must therefore limit or even exclude foods richest in protein such as meat, fish and eggs.