An off-the-shelf supplement may be able to cure hangovers – but only for women, a scientific study has found.

Researchers in the United States found N-acetylcysteine (NAC), a liver-protecting supplement also given to asthmatics and cystic fibrosis sufferers, alleviates hangover symptoms for women.

Men, however, appear to get no benefit at all from the pills.

Purported hangover cures – two paracetamol tablets before bed, having a cup of water between drinks, a Berocca in the morning alongside a full English breakfast – have devout supporters, but few are grounded in scientific research.

The team of academics from St Luke’s University Health Network in Pennsylvania chose to investigate NAC as a potential hangover cure because of its effect on the liver.

Tablets’ effect on liver in the spotlight

“In the liver, alcohol dehydrogenase (ADH) breaks down ethanol to acetaldehyde, a toxic by-product, using coenzymes glutathione and cysteine, which are the limiting reagents in this reaction,” the researchers write in their study, published in Scientific Reports.

“When excessive amounts of ethanol are consumed, the liver is unable to effectively complete this process.

“As glutathione stores diminish, the patient must wait for the liver to make more glutathione to rid the body of the remaining acetaldehyde, a process that can take 8-24 hours.

“Since N-acetylcysteine (NAC) is a precursor to L-glutathione, it has the potential to decrease oxidative stress on the liver during ethanol degradation as a glutathione donor.”

Researchers recruited 49 volunteers and tasked them with sitting in a room and drinking bottles of “5.2% ABV Belgian-style wheat ale”.

After each one, they did a breathalyser test to assess their breath alcohol content and they stopped drinking once it reached 0.1 per cent. A 0.8 per cent reading is the legal drink driving limit in both the US and UK.

At this point, participants were given NAC capsules (three if they drank seven or more beers, two if they drank four to six, and one if it was three or less) and driven home.

A tub of 30 600mg tablets is available from retailers for less than £10.

The now-drunk participants were asked to fill in a questionnaire within one hour of waking up the next morning, rating various symptoms on a scale of one to five.

Sliding scale for hangovers

There was also a scale to assess, in general, how hungover they felt from “Feel like I did not drink” to “So hungover I might die”.

Data showed that women who took NAC felt better in the morning than women who took a placebo, rating their hangovers 3.5 higher.

However, men reported feeling worse after the pills. The gender divide was most stark for nausea and feelings of weakness, the researchers say.

“The study was suggestive of a gender difference with females having improved hangover symptoms after NAC use,” the researchers say.