NAC

NAC itself isn't sold as a supplement in Australia, so our naturopaths focus on finding you the legal option that suits you.

A good fit if

• You came here looking for NAC and want the clear legal answer before you buy anything
• You want a legal cysteine source you can swallow, and you're happy with cysteine, cystine or glutathione instead
• You'd rather get more cysteine from food, since everyday protein already contains it
• You've read about NAC for sperm health and want a naturopath's view on the legal alternatives

Check with us first if

• You already take a cysteine-family product and are thinking about adding another. The 450 mg cysteine cap covers all of them combined.
• You're pregnant or breastfeeding and thinking about glutathione, which carries a label warning: adults only, and not for use in pregnancy.
• You take prescription medicine and want to add any cysteine-family or glutathione product.
• You've been taking an "NAC" product bought online, because it hasn't been assessed under Australian rules.

• N-acetylcysteine (NAC). Best known for: The form almost every trial in this comparison actually used, and the one you can't buy here. Absorption: Not established for the oral route in our sources. Typical use: Not a legal supplement ingredient in Australia. Used in hospitals as an injection or inhaler.
• Cysteine (item 1688). Best known for: The plain amino acid, permitted here as an active ingredient. Absorption: Not tested on its own in any trial we hold. Typical use: Capped at 450 mg of cysteine a day. No outcome trials of its own.
• Cystine (item 1691). Best known for: The stable, oxidised twin of cysteine. Absorption: Not tested alone, only combined with glutathione. Typical use: One 124-person trial, for skin tone, at a dose above our legal cap.
• D-Ribose-L-Cysteine (item 1703). Best known for: A cysteine-delivery form sold overseas as a glutathione precursor. Absorption: No data in our sources. Typical use: Legal here, oral, capped at 450 mg of cysteine. No clinical trials found.
• Glutathione (item 2379). Best known for: The finished antioxidant NAC is taken to try to raise, not a precursor. Absorption: Covered in its own entry, not assessed here. Typical use: Legal here, oral, adults only, not recommended in pregnancy or breastfeeding.
• Whey protein and other high-cysteine foods. Best known for: Ordinary food-based cysteine, with no regulatory cap because it's food. Absorption: Not assessed for this comparison. Typical use: The simplest legal way to get more cysteine, through the diet.

Reference values. There's no Australian recommended intake for cysteine or NAC. The NHMRC reference values cover 25 vitamins and minerals, not amino acids.

Typical supplemental range. There isn't one for NAC itself, because it isn't a legal supplement ingredient here. The cysteine-family ingredients you can buy (cysteine, cystine, cysteine hydrochloride and D-ribose-L-cysteine) share one combined cap of 450 mg of cysteine a day.

Upper level. No upper level is set for cysteine or NAC. Clinical trials of NAC taken by mouth used 600 mg to 4,000 mg a day, all above what an Australian listed medicine can legally contain.

Worth knowing. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Eggs, meat, poultry and fish: A well-known source of cysteine as part of ordinary protein. No verified per-serve figure in our sources
• Dairy, especially whey-based protein: A well-known cysteine source. No verified per-serve figure in our sources
• Legumes, oats and sunflower seeds: A plant-based source of cysteine. No verified per-serve figure in our sources

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Pregnancy and breastfeeding. No safety data exists for NAC itself either way. Glutathione products carry a mandatory adults-only, not-pregnant label warning.
• Stacking cysteine products. Cysteine, cystine, cysteine hydrochloride and D-ribose-L-cysteine share one combined cap of 450 mg of cysteine a day.
• Surgery, especially liver transplant surgery. NAC has been linked to increased blood and clotting product needs during liver transplants.
• Longer than 6 weeks of use. Across 83 studies, stomach pain, nausea, diarrhoea and joint pain were 1.4 to 2.2 times more common.
• Any oral "NAC" supplement bought online. It isn't a permitted ingredient in an Australian listed medicine, so it hasn't been assessed under our rules.