N-acetylcysteine (or NAC) is an amino acid which comes from L-cysteine, one of the 11 non-essential amino acids which form the building blocks of our proteins (1). It is not found in its natural state in either the body or the diet.
Available to the public in the form of dietary supplements for the past few decades, this molecule, discovered in 1899, was studied extensively in the 1990s, particularly in the fields of pulmonology, immunology and neurology (2). It also features in the World Health Organization’s list of essential medicines.
N-acetylcysteine’s strength lies in its versatility: it has an amazing ability to act at various levels in the body, primarily exerting a protective action.
Researchers have highlighted its specific affinity with the pulmonary and bronchial pathways (3). Combined with appropriate medication, NAC offers promising prospects for reducing the intensity and severity of pain and discomfort (4).
N-acetylcysteine has another feature of particular interest to the scientific community: its ability to cross the blood-brain barrier (5). This physical and metabolic filter is designed to isolate the central nervous system from the circulation (and the potentially toxic molecules it transports).
NAC is thus able to access the brain directly, a rarety among synthetic substances, raising considerable hope for problems related to nerve tissue (6-8).
Studies are attempting to clarify how NAC interacts with our immune systems, particularly with certain interleukins (IL-6, IL-8…) as well as with the expression of nuclear factor kappa B, involved in inflammatory processes and cell proliferation (9-10).
N-acetylcysteine also appears to provide valuable support to menopausal women, in whom there’s an inevitable decline in oestrogen levels (11). And as we know, this change predisposes to, amongst others, urinary and vaginal imbalances.
Another subject under investigation is its potential benefits in male and female infertility (12-14).
Another key reason why NAC has gained so much attention is that it is the most direct precursor of glutathione, a tripeptide composed of cysteine, glycine and glutamic acid (15). By enabling the production of cysteine, N-acetylcysteine thus has a direct effect on the body’s glutathione levels (16).
Present in almost all cells of living organisms, glutathione acts as a strong defensive shield. In particular, it ensures that redox potential is maintained within cytoplasm (17).
Primarily stored in the liver, it also ensures important detoxification functions (18). Several studies have examined its role in the metabolism and elimination of potentially harmful compounds such as drugs or cigarette smoke (19-20). In fact, NAC has long been used in conventional medicine in cases of paracetamol (acetaminophen) poisoning (21).
We often see a decline in glutathione levels with ageing, as well as with many forms of neurological, respiratory and metabolic dysfunction (22-23).
Its synthetic nature means that it is unfortunately impossible to boost your NAC intake naturally – by, for example, modifying your diet or lifestyle. Supplementation with N-acetylcysteine is therefore necessary in order to fully benefit from its properties (with the supplement N-Acetyl Cysteine, for example, the daily dose is divided into 3 capsules for greater flexibility and an optimal spread across the day) (24).
Another possibility is a direct intake of glutathione. The problem here is that it is rapidly broken down by enzymes in the gut called gamma-glutamyltranspeptidases, thus minimising its absorption (25).
To get round this problem, you can opt for:
To reduce the effects of oxidative stress on our cells, glutathione is combined in some formulations with recognised antioxidants such as turmeric and grapeseed (the high-performance supplement AntiOxidant Synergy is one such example, delivering a variety of well-known compounds such as green tea, resveratrol and pine bark) (29-30).
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