Acetylcysteine does not prevent hangover, study shows (update)

N-Acetyl-L-Cysteine (NAC)-containing supplements are widely propagated for hangover prevention, although there’s been no scientific evidence backing this claims. First-ever results from a placebo-controlled hangover trial now became available.

The popular supplements are useless. NAC does not prevent hangover.

This blog has written extensively in finnish about a scam product by Rohtos Labs from Oulu. Called SUOJA – formerly Detoxformula -, it contains NAC as main ingredience, and was sold internationally.


What trial?

The world’s first-ever placebo-controlled trial of NAC in hangover prevention was conducted already in August – December 2015 in Pennsylvania, US. Run by the St. Luke’s Hospital and Health Network, it enrolled 62 people and used a crossover design.

49 participants had analysable data. They were randomized in groups of 23 and 26. 2/3 were male, race was not recorded. Alcoholism was an exclusion criterium. Outcome measure was the Hangover Symptoms Scale (HSS), which has 13 items á 4 pts max. The worst (but unimaginable) hangover thus would score 52 pts.

Participants drank beer until reaching a blood alcohol concentration of 0.1. The number of drinks was recorded, and NAC 600mg capsules were given, 1 caps for 3 drinks. The next morning, participants filled out the HSS questionnaire.

The results should make NAC sellers and users feel uncomfortable: NAC and placebo had exactly the same effect. The HSS scores were 0-35 and 0-38, respectively. That means, that hangover really occured and the alcohol dose was sufficient – as should have been the NAC dose.

Still worse, NAC had significantly more side effects than placebo. In the Acetylcysteine group, 22% of users experienced adverse effects, while in the placebo group adverse reactions were registered in only 8%.

These results became available a few days ago through the Study results-tab of the trial’s registry entry at Ahead or in place of a peer-reviewed publication, they went completely unnoticed by the supplements community.

This demonstrates again, how dietary supplements are used without justification, based only on lab studies. Rarely such useless and potentially hazardous “biohacks” get so cleanly refuted as in this case.

***UPDATE 9.7.2018***

The second, bigger NAC study with 200 participants was now terminated early. Obviously it was deemed futile to try to demonstrate a non-existent effect.


37 thoughts on “Acetylcysteine does not prevent hangover, study shows (update)

  1. I have used nac for hangover prevention and I suggest it is 60-70 % effective in my experience. That the trial mentioned herein is flawed in that participants are administered the supplement after they have consumed all the alcohol. At the end of the evening. That the literature which accompanies NAC for hangover prevention states it should be taken an hour in advance of and then every hour or so, during an evening of drinking. Takne inthis manner, you are essentially absorbing nac, throughout the night, to help it build those antioxidants on the fly. That taking it after drinking is too late, as all the damage from acetylaldehyde has already been done. Hence the negative trial results. Well, that’s my anecdotal 2 bits. I have used it, and with decent success.

    1. It’s a common feature of alternative treatments, wonder supplements and other “biohacks”, that failures are blamed on the user. “Would you’ve taken it before, it would have worked!” – “Didn’t you know it can not be taken together with X?” and so on.

      There is no credible “literature” to accompany any NAC product for hangover prevention. Simply because it’s not scientifically tested. The only thing we have in humans is this single study, and it’s negative. I could go on with a tractate about GI physiology to show you got the wrong idea how these substances “work”. But that would be nothing more than another rant w/o relevance for the question.

      If someone has a link to reliable information, please put it here for discussion. So far most does come from people with a commercial interest, not from scientific research.

      1. Love it how you’re in denial. A single study that was conducted in a wrong way “proved” something, so people’s opinions don’t matter to you. There’s so many things wrong with this premise I can’t even begin to explain them.

        1. OK.

          Why is this?

          There have been so many claims that I’m getting tired. No-one could present any proof or even a plausible theory why it should be taken before.

          Until there’s some more detail than just plain denial, I’m thinking about suspending comments to this post.

          Still waiting.

  2. In my opinion the study you have linked is more ore less worthless because it has too less participiants and is using only a Median Value for the score. At least total Hangover symptom score is 10 vs 13 and nauseated score is 0 vs 1 for NAC vs Placebo. Though its insignificant the NAC users had a little less hangover than placebo users.

    Second is what Tony said. You should take it before drinking, at least for mice it had a negative effect taking NAC after drinking. (liver damage wise)

    Third, I am getting an alcohol flush reaction when drinking alcohol and for me it is greatly reduced by taking NAC. Most probaly NAC safes a little from Acetataldehyde intoxication.

    I am not really saing it will help against hangover for most of the people but it can have other positive effects and for people like me who gets an alcohol flush reaction the hangover is probaly reduced greatly.

    1. The study had enough power to detect meaningful differences.

      The side effects difference had trend-level significance (p=0,09 roughly calculated). If there had been a few more participants (1-2 more), it would have reached significance.

      For power calculation, see for example the good tutorial in Critical Care, which is already a classic and should be understood before claiming anything about “too small” studies. Other literature about biostatistics will tell the same (but is harder to read, in my opinion).

  3. This study is complete nonsense. Participants were given NAC at the end of the night, after drinking. Of course it’s not going to prevent a hangover if administered after a night of heavy drinking. I use NAC regularly, and it must be taken 30 minutes to an hour prior to drinking, with pills taken throughout the night with each drink. It works wonderfully if taken properly… I’d say about 70-80 percent reduction in hangover symptoms a night after heavy drinking. This study is ridiculous.

    1. I understand that taking nac after drinking can be harmful and cause damage to the liver, but how long after drinking can one take nac? I need to drink on a daily basis and I would like start taking nac.

  4. I have zero commercial interest in NAC, but I do have an interest in my ability to wake up without a hangover in the morning, and my results, as indicated were reasonably worth while. Prior to taking NAC, I’d consistently wake up hungover after a night of drinking. As I got older, I could tolerate even less alcohol. Taking NAC had immediate effect for me.

    Anyway, I already admitted my results were around 70% effective, and agree they are purely anecdotal, but for you to suggest I am somehow doing it for “commercial interest”, or that I am somehow not credible, is plainly false. It worked for me. My experience is very credible. More credible than the trial I just read which was- by and large- a waste of time in the manner it was conducted, as well as your own “unfounded opinion”.

    I was interested to read the trial results, but the manner in which the trial was done rendered it usesess. Gastrointestinal physiologies notwithstanding.

    1. I didn’t mean you with that. To expect that such a comment would be in commercial interest, would be silly, as this blog is too unimportant…and I plainly hate discussions where others are un(dis)provably blamed for sinister agendas.

      Apologies if that was misunderstandable.

      1. Ha – my apologies in return.

        As soon as I submitted my response, I read your reply more fully and felt my reply might have been deemed a little defensive, so sorry about that.

        I still stand my my personal experience using NAC.

        Have honeslty been trying to find supporting literature for my experience which, as you indicated, does not exist, so was just a little disappointed at how they arrived at their conclusions. The trial meant little to me.

        I have also read literature that they adminster NAC for tylenol overdose, so it must have some antioxidant / liver benefit. I am sure there is also literature indicating its benefit in improving liver function, so really a harmless supplement to take if you are planning to drink alcohol.

  5. NAC definitely improves hangovers (not perfect but vast improvement) but it must be taken in advance. Again no commercial interest.

    1. Again: That was not aimed at commenters.

      If there is any reliable source for the claim that it works if taken *before*, please let me know. Otherwise it’s irrelevant for our question, because this post is about science and not personal views.

      1. I found this particular article/blog/report doing a search for NAC uselfulness in hangover prevention. Guess I was trying to find something more concrete than personal anecdotal experience.

        Haven’t actually used NAC in a while, yet my drinking has generally increased because I now do a fair bit of homebrewing.

        The above report makes assumptions relevant to my use of NAC. I left comments that I think refute, or at least, raise some questions over the validity of how the trial was carried out, and the conclusions drawn.

  6. In the absence of high-quality evidence I’m not going to pretend to know NAC definitely works and I haven’t tried it myself. But every anecdotal account of using NAC to prevent hangovers on the internet speaks of taking the supplement BEFORE and often during and after drinking. If it is indeed true that in this study they had participants take NAC after finishing drinking then their null result doesn’t prove anything. Mechanistically we should EXPECT a null result because much if not most of the alcohol should’ve already been converted to acetaldehyde, and, indeed much of the acetaldehyde may already have been converted to acetic acid.

    1. You’re right about the evidence-based view. It’s often forgotten that the best available evidence has to be used. If there are no good studies, anecdotal evidence is the best we have and must be used. I have to keep that in mind.

      On the other hand, the question here was not before or after. That’s beyond scope and would require comparative studies.

      I’m afraid there will be no further studies on NAC for alcohol soon, because the best we have (one with NAC taken after drinking) was negative and there’s no great interest in that topic from the industry. The pharmaceutical industry, which usually sponsors bigger RCTs, not the supplement industry which usually relies on prejudice and half-truths.

  7. If the subjects only drank to a blood alcohol content of .1%, I don’t expect there would be much hangover, and the test would not be very sensitive. And looking at the study results, there was very little reported hangover symptoms in either group. All of the 1-4 symptom ratings were only 1 for both groups, except for nausia, which was 0 in the NAC group.

    In my personal experience, NAC does work, specifically when the alcohol amount is enough to be considered very drunk.

    This article draw too positive and unreserved a conclusion from a single, seemingly flawed study.

  8. The study does, though, seem to show that nausea is less in the NAC group, while other effects are equal. I ask you, could it be that there is more than one process at work in a hangover? Consider the way NAC is used by hospitals to treat certain overdoses, and it’s method of action.

    Could it be that nausea symptom is caused by the buildup of toxins in the brain, which NAC combats by increasing glutathione, while the dehydration symptom is caused by another process that NAC does not address, namely the production of vasopressin?

    The article does not contemplate this. I use NAC specifically for the nausea prevention and do not expect it to prevent dehydration.

    The update section in particular seems un-objective when it states that the reason for a new study’s discontinuation is “obvious” when actually the reason is not obvious to us. The writer seems to have an axe to grind.

    1. That makes sense to me! I still feel some effects of a hangover (tiredness, soreness etc.), but the worst symptomd—the nausea and lack of appetite (and to some extent, the post-alcohol anxiety)—are pretty much nonexistent. I was almost blackout drunk this Saturday, yet shockingly functional yesterday (it’s Monday now). I slept at my friend’s place, and he’s STILL feeling the after effects today…
      Actually, the last time I had a proper hangover was before I started taking NAC (and mind you, it was so bad that I couldn’t sleep and started experiencing panic attacks, trembled and felt horribly weak, had to take an ice cold shower because I felt feverish, was hardly able to swallow food, and almost vomited several times), and I’ve been on several binges since then.
      I originally started taking high doses of NAC to see if it would help me with my skin picking disorder and trichotillomania (it has somewhat alleviated my body-focused repetitive disorders thus far). So finding out that it can prevent hangovers if taken about 30+ minutes beforehand was a nice surprise! After researching it, I do avoid taking any after I have started drinking, and about 16-24 hours afterwards, since apparently it can have the opposite effect of making ethanol more toxic for your body if used too soon after drinking.

  9. I took NaC for a month to see if it helped reduce my obsessive tendencies. It was a while ago and I can’t remember if it helped with that (I think it did a bit) but I remember thinking, huh, I don’t get hangovers anymore and looked into it and it was totally a thing. I wasn’t expecting it to have any affect on hangovers but it was pronounced enough for me to notice.

    1. Vitamin C? Says who?

      I understand that my blog is now on Google pos. 1 for “acetylcysteine hangover”. That’s why there were hundreds of pageviews around New Year’s Eve. It even surpassed my all-time top posts about BEMER and the HumanCharger scam.

      This brought new commenters who aren’t familiar with this blog. To make it short:
      I’m not writing about opinions, but science. If someone makes up a disease, symptom or treatment, I will comment this way. Please deliver references for such claims, otherwise it’s boring and wasted.

  10. “The best way to prevent symptoms the next day is, of course, to drink sensibly. But if someone gets caught up in celebrations and has a few more than they normally do, it’s very likely they will wake up with symptoms such as thirst, fatigue, nausea, headache, dizziness, and shakiness. What is a good hangover cure at home? Can NAC for alcohol help with these symptoms?

    The supplement works best if it is taken before alcohol ingestion. The use of NAC for hangover can be dangerous if it is taken after alcohol consumption. This is because, following a night of drinking, the body goes into overdrive and produces more glutamine than required. If the supplement is taken during this natural glutamine rebound, the excessive levels in the body can cause symptoms such as poor sleep, anxiety, tremors, restlessness, and high blood pressure.”

      1. I wouldn’t say “dangerous”, but instead of it having hepatoprotective effects (when taken before alcohol consumption), it has hepatotoxic effects (when taken after). I.e. it just adds to the damaging effects of alcohol if ingested too soon after alcohol consumption, so to be on the “safe” side, it may be best to avoid NAC supplementation for up to 24 hours after drinking alcohol.

        As for some amino acids being able to have negative effects on the body depending on other factors (in this case an autosomal recessive genetic disorder): haven’t you ever heard of phenylketonuria (PKU)?
        Why do you think there are warning texts for “contains phenylalanine” on certain products? It’s warning phenylketonurics about an essential amino acid.

        And as for a specifically “dangerous” amino acid: β-Methylamino-l-alanine (BMAA) is a neurotoxin that acts on the glutamate receptors.

        And it’s not an issue of glutamine overdrive, but GLUTAMATE overdrive. Glutamate is a neurotransmitter, and pathologically high levels of glutamate is absolutely harmful as it causes excessive stimulation that damages and can kill nerve cells: look up “excitotoxicity” to read more about this process.

        1. Thanks for a high-qual (but somewhat inconsistent) comment.

          Obviously, with amino acid I meant amino acids from which our organism is built and we get, mostly, from food. Glutamine is usually produced by the human body, and therefore highly unlikely to be of concern. I felt this cannot be discussed with somebody who confuses Glutamine and Glutamate.

          It’s clear that not everything that carries a -COOH and -NH2 is non-toxic. And with “inconsistent” I mean your remark about PKU. As you notice correctly, the problem is the disease, not the Phe itself. Phenylalanine is needed for a lot of syntheses (roughly most important, the catecholamines) and is an essential amino acid. The mark on food products and beverages is for those who have PKU, which is, in central Europe, a quite common genetic defect. (Especially here in Finland it’s generally unknown even to many physicians, because the finnish gene pool was long isolated and enriched in many “exotic” genetic defects, but has no PKU.)

          Is there any source for your claim of hepatic probs, besides the over-interpreted rodent studies?

      2. Wow you’re somewhat of a smart ass unnecessarily so.
        Here’s the one place the information was obtained from but I’ve researched this for awhile because “I” was wondering why i would feel like shit taking NAC the next day AFTER excess drinking more so than went i took nothing. So i read the rodent studies and searched hundreds of places for others anecdotal experiences.
        Come down from your fckin might high horse genius. There’s information that may have escaped your massive IQ.

        Here’s where my quote came from and it was just a simple counter to the flawed meaningless rodent study.

        1. yes, he has a terrible bedside manner. And the study in question only proves that taking NAC after alcohol has little effect. We obviously need another experiment that compares what happens taking it beforehand, and there is plenty of anecdotal evidence and self-reporting about the efficacy of the latter. I also taking NAC for a year before drinking, and my partner, and we haven’t had a hangover once during that period.

        2. I agree with you, the editor is obviously not a very nice person. There’s plenty enough anecdotal evidence of NAC’s efficacy taken BEFORE drinking, even in this blog. It works perfectly well for me, and wouldn’t drink without having taken it beforehand. I can’t believe how the study discussed is so flawed in assuming that taking it after would help, it seems arbitrary.

  11. I take a double dose the next day of about 1800mg on an empty stomach with 1000mg of Vit C along with a multi vit, cod liver oil and magnesium, then if I can get a nap in, get up and repeat the NAC and vit C dose within an hr of doing that 2nd dose I usually feel pretty good. So I do think it can reduce the duration of a hangover by a few hrs but that’s as good as I can get from it. I once gave a friend 1200mg one night when he was plastered before he went to bed and he texted me the next day saying “what did you give me last night? I feel amazing, I no hangover at all.” So, it may affect different individuals to different degrees.

  12. I do find that NAC helps somewhat but more so it’s a B vitamin complex that works better. I take the two in combination. Thing is though, if I can drink more with less hangover symptoms all that happens is that I push my boundaries to find the new point that I can drink to without feeling too bad the next day with the supplements help. That’s not a positive development. I try and stay on kava as much as possible but alcohol is my main weakness.

  13. This is a flawed study, a conclusion cannot be determined due to the errors made here. I would look at the countless other studies on NAC and alcohol use that have been conducted properly.

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