Food supplements containing the substances N-acetylcysteine, L-cysteine and/or L-cystine are sold in the Netherlands. These supplements are intended to detoxify the body. When used in accordance with the instructions on the label, some of these supplements may be ingested in quantities that can cause side effects. For this reason, RIVM advises users not to take too much of a supplement.
Adults can take up to a maximum of 1,200 mg of N-acetylcysteine or 900 mg of L-cysteine or L-cystine per day without experiencing any side effects. For children from the age of 2 to 18, the maximum quantity is lower. Furthermore, RIVM recommends against giving these supplements to children under the age of 2.
Registered as a drug
The substance N-acetylcysteine is also registered as an expectorant drug. Taking the food supplements together with this drug is not recommended, as people may take too much. This may result in side effects that can include gastrointestinal symptoms.
Safety assessment
At the request of the Dutch Ministry of Health, Welfare and Sport, RIVM has assessed the safety of N-acetylcysteine. The human body converts N-acetylcysteine into the substances L-cysteine or L-cystine. As the supplements may also contain these substances, RIVM has assessed all three of these substances.