N-ACETYLCYSTEINE SUPPLEMENTATION

N-acetylcysteine is supplemented as N-acetylcysteine or as cysteine. The acetylated form provides better bioavailability.

REFERENCE VALUES

There are no harmonized maximum intake levels for it as a dietary supplement at the European level.

Intake and deficiencies

Low cysteine levels are common in elderly people, mainly when they suffer from chronic diseases.

L-cysteine is a non-essential amino acid that is synthesized in the body and supplied in foods.

Intake. Cysteine is found in most protein-rich foods, such as those of animal origin (pork, beef, chicken, turkey, duck, eggs, milk, etc.).

Endogenous synthesis. It is formed from methionine and is one of the few sulfur-containing amino acids. Cysteine is a glutathione and taurine precursor. The sulfur-containing amino acids methionine and cysteine supply most of the sulfur the body needs. Methionine is the essential amino acid found in the smallest amounts in all foods, especially vegetables, and its deficiency can be common in chronic diseases.

Deficiencies. A study conducted by Blanco et al observed that homeostatic regulation of cysteine and glutathione decrease with age, with this decline appearing in men before women (Blanco 2007).

Another study, in this case conducted in India with healthy subjects, observed that there is an inverse relationship between L-cysteine capture and transport by erythrocytes and age. (Rizvi 2008).

Although classified as non-essential, this amino acid can be essential in children, the elderly, and individuals with metabolic diseases or suffering from malabsorption syndromes.

N-acetylcysteine (NAC) has a good safety profile, even at doses as high as 1.5–2.0 g, with mild and infrequent side effects (nausea, heartburn, diarrhea, itching, hives, etc.). The usual treatment dose is 600–1,200 mg. In asthma, NAC can cause bronchospasm.

BIBLIOGRAPHY

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FOODS WITH N-ACETYLCYSTEINE

Cysteine is found in most high-protein foods such as animal sources (pork, beef, chicken, turkey, duck, eggs, milk, etc.). It can also be found in plants of the Allium genus such as garlic, onion or leek.