NAC Supplements · Ireland · Updated June 2026
N-Acetyl Cysteine (NAC) is one of the most extensively studied supplement compounds in nutritional science, valued for its role as a precursor to glutathione. This page covers what NAC is, the published evidence, how to choose between brands and doses, and the full NAC and antioxidant range available with tracked delivery across Ireland.
At a Glance
NAC (N-Acetyl Cysteine) is a stable form of the amino acid cysteine and a precursor to glutathione, described in biochemistry literature as the body's main intracellular antioxidant. In Ireland, NAC is sold as a food supplement regulated by the FSAI, not as a medicine. The most-studied human dose is 600mg, the standard capsule strength stocked here. Human evidence is strongest for glutathione support and antioxidant biomarkers; broader health benefits in healthy people are not established. NOW Foods NAC 600mg (with selenium and molybdenum) is €22.95 and Swanson NAC 600mg is €21.95, both with tracked delivery from Dublin and Irish VAT (13.5%) included.
N-Acetyl Cysteine (NAC) definition: NAC is the acetylated form of the amino acid L-cysteine, a sulphur-containing compound that the body converts to cysteine and uses as the rate-limiting building block for synthesising glutathione.
In a hurry? The quick picks
NAC + Selenium (EU antioxidant claim)NOW Foods NAC 600mg600mg NAC with selenium & molybdenum · 100 or 250 veg caps
Lowest price single-ingredient NACSwanson NAC 600mg600mg N-Acetyl Cysteine · 100 caps
Prefer direct glutathioneGlutathione rangeFor those who want glutathione rather than a precursor
See the full NAC & antioxidant range at Probiotic.ie →
Fast Facts — NAC
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What it is: N-Acetyl Cysteine, a stable form of the amino acid cysteine
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Primary role in research: precursor to glutathione, the body's main intracellular antioxidant
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Dietary sources: cysteine is found in high-protein foods; NAC itself is supplement-derived
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Supplement source: synthesised; capsules are typically vegan-suitable (hypromellose shell)
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Most-studied dose: 600mg, taken one to three times daily in published trials
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Standard retail strength in Ireland: 600mg per capsule
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Is it a medicine? No. Sold as a food supplement under FSAI guidelines
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Vegan suitable? Yes for NOW Foods and Swanson NAC (plant cellulose capsule)
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Irish regulatory status: food supplement under FSAI guidelines, not a medicine
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Irish VAT on supplements: 13.5%
Research Context — Not Product Claims
The research discussed on this page relates to NAC and its constituent compounds as studied in published settings. It is not a claim that any specific product produces these effects. These are food supplements, not medicines. No authorised EU health claim is made for NAC itself; where selenium is present, only its EU-authorised claims apply.
NOW Foods NAC 600mg — N-Acetyl Cysteine with Selenium
The 600mg dose used across most published NAC trials, paired with selenium from L-selenomethionine, which carries EU-authorised antioxidant and immune health claims.
600mg NAC
+ Selenium & Molybdenum
100 or 250 veg caps
Vegan
Ships from Dublin
✓ Buy NOW NAC 600mg →
Food supplement, not a medicine. Irish VAT 13.5% included. Tracked Irish delivery, free over €75.
Mechanism
What NAC is and how it works
Glutathione is a tripeptide built from three amino acids: glutamate, glycine and cysteine. Of these, cysteine is the rate-limiting precursor, meaning the body's ability to make glutathione is constrained mainly by how much cysteine is available.
NAC is a stable, well-absorbed form of cysteine. Once inside cells it is deacetylated to free cysteine, which then feeds glutathione synthesis. This is why published literature describes NAC's primary antioxidant role as raising intracellular glutathione rather than acting as a direct antioxidant itself.1
🔁
Glutathione precursor
Supplies cysteine, the rate-limiting building block for glutathione synthesis inside cells.
Evidence level: well-documented mechanism
🛡️
Antioxidant support
Glutathione is the body's main intracellular antioxidant, central to cellular redox balance.
Evidence level: established biochemistry
🫁
Mucolytic property
NAC breaks disulphide bonds in mucus glycoproteins, the basis of its licensed pharmaceutical use.
Evidence level: established (pharmaceutical context)
⚗️
Sulphur amino acid pathway
As a sulphur-containing compound, NAC participates in cysteine and methionine metabolism.
Evidence level: established biochemistry
Evidence
What the published evidence shows
NAC has one of the longest research histories of any supplement compound, studied across respiratory health, oxidative stress and physical performance. The honest summary is that mechanism and biomarker evidence is strong, while clear benefits in healthy people are less settled.
Systematic Review
A 2023 systematic review of controlled trials in adult men concluded that NAC supplementation may help regulate glutathione homeostasis and antioxidant defence, and may support exercise performance, while explicitly noting that further studies are needed to clarify its relevance.
Fernández-Lázaro D, et al. Influence of N-Acetylcysteine Supplementation on Physical Performance and Laboratory Biomarkers in Adult Males. Nutrients. 2023;15(11):2463. PMID 37299425.
RCT — Conditional Finding
A randomised trial found NAC increased exercise performance and reduced oxidative stress only in individuals who started with low glutathione levels, not in those with normal levels. This is a key nuance: NAC's effect appears to depend on baseline status, not a universal boost.
Paschalis V, et al. Free Radic Biol Med. 2018;115:288-297. PMID 29233792.
Limitation
Much NAC evidence comes from clinical populations or specific deficiency states, not healthy adults taking it preventively. There is no authorised EU health claim for NAC itself, and a glutathione comparison trial actually found a sublingual glutathione form outperformed NAC on the GSH/GSSG ratio, showing the "NAC is best for glutathione" claim is not clear-cut.
Schmitt B, et al. Redox Biol. 2015;6:198-205. PMID 26262996.
600mg
Most-studied human dose
3
Amino acids in glutathione
25mcg
Selenium in NOW formula (45% NRV)
13.5%
Irish VAT on supplements
Buying guide
Choosing a NAC supplement: dose, brand, format
Two decisions matter most: dose and whether you want NAC alone or NAC with cofactors. On dose, 600mg per capsule is the standard and matches the bulk of published trials, so there is rarely a reason to pay for anything unusual.
On format, the practical split is single-ingredient NAC versus NAC paired with selenium. Selenium is the cofactor for glutathione peroxidase, the enzyme that actually uses glutathione, and it carries genuine EU-authorised health claims, which a plain NAC capsule cannot make.
| Option |
NAC dose |
Extras |
Caps |
Price |
Best for |
| NOW Foods NAC 600mg |
600mg |
+ Selenium + Molybdenum |
100 / 250 |
€22.95 |
NAC with an EU-authorised antioxidant claim via selenium |
| Swanson NAC 600mg |
600mg |
NAC only |
100 |
€21.95 |
Lowest-cost single-ingredient NAC |
| Glutathione (direct) |
N/A |
Reduced / liposomal forms |
Varies |
From €19.95 |
People who prefer glutathione over a precursor |
Comparison
NAC vs glutathione
This is the most common question buyers ask, so it is worth being straight about it. Oral glutathione has historically shown poor stability in the gut, which is the original argument for taking NAC, a precursor the body uses to build glutathione where it is needed.
The evidence is not one-sided, though. Newer sublingual and liposomal glutathione forms change the comparison, and at least one crossover trial found a sublingual glutathione form raised the GSH/GSSG ratio more than NAC did.3 For most people the choice comes down to cost, shelf stability and preference rather than a clear evidence winner. Our full NAC supplement guide goes deeper on this.
Research Context — Not Product Claims
Research referenced here relates to NAC and selenium as studied compounds and does not constitute a claim that any product on this page produces a specific health outcome. Food supplements, not medicines.
Swanson NAC 600mg — Single-Ingredient N-Acetyl Cysteine
A straightforward 600mg NAC capsule at the lowest price point in the range, for buyers who want NAC alone without added cofactors.
600mg NAC
Single ingredient
100 caps
Best value
Ships from Dublin
✓ Buy Swanson NAC 600mg →
Food supplement, not a medicine. Irish VAT 13.5% included. Tracked Irish delivery, free over €75.
Wider range
The wider antioxidant range
NAC sits within a broader antioxidant range stocked for Irish delivery. These compounds work through different pathways, so people often pair or rotate them depending on what they are looking for.
🧬Glutathione
The antioxidant NAC helps the body produce, available here in direct oral forms.
View glutathione →
⚡Alpha lipoic acid
A dual water- and fat-soluble compound studied for its role in cellular redox balance.
Stocked in this collection
🌿Milk thistle
A traditional botanical, commonly paired with antioxidant routines.
Stocked in this collection
🔋CoQ10
Involved in mitochondrial energy production and studied as an antioxidant.
Stocked in this collection
Ireland
NAC supplements in Ireland: rules, VAT, delivery
In Ireland, NAC is sold legally as a food supplement and regulated by the Food Safety Authority of Ireland (FSAI), not as a medicine. Health claims on supplements are governed by EU Regulation 1924/2006, which is why a plain NAC product carries no authorised health claim while a selenium-containing one can.
VAT on food supplements in Ireland is 13.5%, included in the prices shown. Orders ship from Dublin by tracked DPD delivery, usually next working day, and free over €75.
Product Details Verified
Prices and specifications on this page — NOW Foods NAC 600mg (600mg NAC plus 25mcg selenium and 50mcg molybdenum, 100/250 veg caps, €22.95) and Swanson NAC 600mg (600mg NAC, 100 caps, €21.95) — were verified from current product pages and supplier information. Always check the current label before use, as formulations and pricing may change.
Ships From Ireland — No Customs Charges
All stock dispatches from Dublin, so there are no customs duties on these orders, including after the 1 July 2026 EU customs rule change that affects parcels arriving from outside the EU. Why this matters from July 2026 →
Key Facts — NAC Ireland
- NAC (N-Acetyl Cysteine) is a stable form of the amino acid cysteine and a precursor to glutathione.
- NAC is not a medicine in food supplement form in Ireland; it is regulated by the FSAI.
- The most-studied human NAC dose is 600mg, the standard retail capsule strength in Ireland.
- A 2023 Nutrients systematic review (Fernández-Lázaro et al., PMID 37299425) found NAC may support glutathione homeostasis but called for more research.
- A 2018 RCT (Paschalis et al., PMID 29233792) found NAC improved performance only in people with low baseline glutathione, not universally.
- There is no EU-authorised health claim for NAC itself; selenium, present in the NOW formula, carries authorised antioxidant and immune claims under EU Regulation 1924/2006.
- NAC and glutathione are both sold here; evidence on which raises glutathione most is mixed.
- Irish supplement VAT is 13.5% and is included in listed prices.
- NOW Foods NAC 600mg (€22.95) and Swanson NAC 600mg (€21.95) are available from Probiotic.ie with tracked delivery from Dublin.
FAQ
Frequently asked questions
What is the best NAC supplement in Ireland?
The most-stocked NAC dose in Ireland is 600mg per capsule, the dose used across most published human NAC trials. The two highest-volume options here are NOW Foods NAC 600mg (which also includes selenium and molybdenum) and Swanson NAC 600mg (single-ingredient, lowest price). Both are vegan-suitable. "Best" depends on whether you want NAC alone or NAC paired with selenium, which carries an EU-authorised antioxidant claim.
What does NAC do in the body?
NAC is a stable form of cysteine. Once absorbed it converts to cysteine inside cells, and cysteine is the rate-limiting building block for glutathione, the body's main intracellular antioxidant. A 2023 review in Nutrients (Fernández-Lázaro et al., PMID 37299425) summarised that NAC may help maintain glutathione homeostasis, while noting more research is needed in healthy populations.
Is NAC legal to buy in Ireland?
Yes. NAC is legally sold as a food supplement in Ireland and regulated by the Food Safety Authority of Ireland (FSAI). It is sold under FSAI food supplement guidelines and EU Regulation 1924/2006 on health claims.
What is the correct NAC dosage?
The dose used most consistently across published human trials is 600mg, taken one to three times daily, typically 600 to 1,200mg per day with food. Most Irish retail NAC products, including NOW Foods and Swanson, provide 600mg per capsule. Trial dose is not a product claim; follow the label and consult a pharmacist if you take prescription medication.
Should I take NAC or a glutathione supplement?
Both are sold in this range. Oral glutathione has historically shown poor stability in the gut, which is why NAC, a precursor, is a common alternative. Evidence on which raises glutathione most is mixed, and newer liposomal and sublingual glutathione forms complicate the comparison. It is a personal choice on cost and preference, not a medical recommendation.
Why does some NAC contain selenium?
Selenium is a required cofactor for glutathione peroxidase, the enzyme that uses glutathione to neutralise reactive oxygen species. NOW Foods NAC 600mg includes 25mcg selenium from L-selenomethionine. Under EU Regulation 1924/2006, selenium carries the authorised claims that it contributes to the protection of cells from oxidative stress and to the normal function of the immune system.
Are there side effects to taking NAC?
At oral supplement doses NAC has a long-documented safety record. The most common effects are mild gastrointestinal symptoms such as nausea or stomach discomfort, more likely on an empty stomach, so taking it with food helps. If you take prescription medication, particularly nitroglycerin or blood pressure medication, consult your doctor or pharmacist first.
What other antioxidant supplements are in this collection?
Alongside NAC, the range includes glutathione, alpha lipoic acid, milk thistle, CoQ10 and selenium-containing formulas from brands including NOW Foods, Swanson, Doctor's Best and Healthy Origins, all stocked for tracked delivery within Ireland.
How fast is delivery on NAC supplements in Ireland?
Orders dispatch from Dublin by tracked DPD delivery, with most arriving the next working day within Ireland and free delivery over €75. Because stock ships from within Ireland, there are no customs charges, including after the 1 July 2026 EU customs change.
Where can I buy NAC in Ireland?
NAC supplements are available from Probiotic.ie, an Irish-owned specialist store dispatching from Dublin, including NOW Foods NAC 600mg from €22.95 and Swanson NAC 600mg from €21.95, in 100 and 250 capsule sizes, with Irish VAT included and tracked nationwide delivery.
Read more
DG
Darren Grant — Managing Director, Probiotic.ie
Darren runs Probiotic.ie, an Irish-owned specialist supplement store, with a focus on evidence-led product information and compliance with FSAI and EU food supplement rules.
This page is for educational purposes only and does not constitute medical advice. NAC and the other products listed are food supplements regulated under FSAI guidelines and are not intended to diagnose, treat, cure, or prevent any disease or medical condition. If you have persistent or worsening symptoms, consult a GP or pharmacist. If you are pregnant, breastfeeding, or taking medication, seek professional advice before use. Probiotic.ie is regulated under FSAI food supplement guidelines.
Sources
- Fernández-Lázaro D, Domínguez-Ortega C, Busto N, et al. Influence of N-Acetylcysteine Supplementation on Physical Performance and Laboratory Biomarkers in Adult Males: A Systematic Review of Controlled Trials. Nutrients. 2023;15(11):2463. PMID 37299425. DOI: 10.3390/nu15112463. — pubmed.ncbi.nlm.nih.gov/37299425
- Paschalis V, Theodorou AA, Margaritelis NV, et al. N-acetylcysteine supplementation increases exercise performance and reduces oxidative stress only in individuals with low levels of glutathione. Free Radic Biol Med. 2018;115:288-297. PMID 29233792. DOI: 10.1016/j.freeradbiomed.2017.12.007. — pubmed.ncbi.nlm.nih.gov/29233792
- Schmitt B, Vicenzi M, Garrel C, Denis FM. Effects of N-acetylcysteine, oral glutathione (GSH) and a novel sublingual GSH form on oxidative stress markers: A comparative crossover study. Redox Biol. 2015;6:198-205. PMID 26262996. DOI: 10.1016/j.redox.2015.07.012. — pubmed.ncbi.nlm.nih.gov/26262996
- European Commission. EU Register of nutrition and health claims (Regulation (EC) No 1924/2006) — selenium authorised claims. — EU health claims register
- Food Safety Authority of Ireland (FSAI). Food supplements legislation and guidance. — fsai.ie/legislation/food-supplements
