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N-acetyl cysteine (NAC) supplements tested by


NAC (N-Acetyl-Cysteine) powder can be stored in a closed container at room temperature (away from high heat or humidity) for at least two months, and possibly longer, without spoiling or degrading. Small amounts of NAC may degrade, over longer periods of time, into a by-product called di-NAC — however, this substance is not known to be harmful. The sulfur in NAC may cause a slight "rotten egg" odor if some of the NAC oxidizes, but this does not indicate a significant loss of NAC. If you are concerned about degradation, consider capsules or tablets, as they are likely to be more stable than powder.

See ConsumerLab's NAC (N-Acetyl-Cysteine) Supplements Review for details, as well as our tests of popular NAC supplements, our Top Picks, and the FDA's latest position on NAC.

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