Kudzu and binge drinking: what the new UCSF trial found and what it does not show

Kudzu is a climbing vine whose root has a long history in traditional East Asian medicine. A new randomised trial has now put a standardised extract of it in front of a much wider audience. Published in the American Journal of Psychiatry on 4 November 2026, the University of California, San Francisco (UCSF) trial found that adults with alcohol use disorder who binge drank had fewer binge-drinking days when they took kudzu extract before expected heavy drinking than when they took placebo.

A question that normally belongs to prescription medicines is being asked of a supplement ingredient, so the details matter: the dose, the product, the people studied and the size of the effect.

The short answer: in 120 adults with alcohol use disorder who binge drank at least weekly, 2 g of kudzu extract taken on days when binge drinking was expected reduced binge-drinking days compared with placebo (incidence rate ratio 0.73, 95% confidence interval 0.54 to 0.99), and the reduction was still present three months after treatment ended. The primary result only just reached statistical significance, a smaller 19-person trial found no benefit over placebo, and a product bought over the counter should not be assumed to match the extract used in the trial.

What the trial did

This was a phase 2b, double-blind, placebo-controlled trial. A total of 120 adults with alcohol use disorder (AUD) who binge drank at least once a week were randomised 1:1 to oral kudzu extract or matching placebo for 12 weeks. For men, binge drinking meant five or more drinks on one occasion, and for women four or more. Participants took 2 g of the extract on days when binge drinking was anticipated, at least 2.5 hours beforehand, rather than every day. Everyone also received brief weekly counselling. People had to report recent sex under the influence of alcohol, people with another severe substance use disorder were excluded, and the trial ran in San Francisco. The primary outcome was the number of binge-drinking days in the past week.

The trial is registered as NCT03709043 and was funded by the US National Institutes of Health. The paper says the study was conducted under an FDA investigational new drug exemption and cites pre-IND number 139735. ClinicalTrials.gov lists the kudzu arm as a drug.

What it found

• Retention was high: 88% completed the trial and 84% of weekly follow-up visits were completed (1,215 of 1,440).
• Primary analysis (everyone as randomised): kudzu reduced binge-drinking days against placebo, incidence rate ratio 0.73 (95% confidence interval 0.54 to 0.99). In an as-treated analysis of people who took the product at least 2.7 days a week, the estimate was stronger, 0.58 (0.38 to 0.89).
• Average binge-drinking days a week fell from 2.15 to 1.42 in the kudzu group and from 2.15 to 2.06 on placebo.
• The proportion of weeks with any binge drinking fell from 88% to 58% on kudzu and from 88% to 81% on placebo. The relative risk in the as-randomised analysis was 0.79 (0.62 to 0.99).
• Phosphatidylethanol (PEth), a blood marker of sustained heavy drinking over the previous few weeks, was lower in the as-treated analysis only (relative risk 0.82, 0.67 to 0.99). It was not significantly lower when everyone was analysed as randomised.
• Number of drinks in the past 30 days was not significantly lower (relative risk 0.70, 0.47 to 1.03). Ethyl glucuronide, a urine marker of recent drinking, was not lower.
• Three months after treatment ended, self-reported binge-drinking days remained lower than on placebo (incidence rate ratio 0.68, 95% confidence interval 0.47 to 0.97).
• Safety: the overall frequency of adverse events was similar between groups, and no serious adverse event was attributed to kudzu. One serious event, myocarditis, occurred in a participant assigned to kudzu after treatment ended and was judged unrelated.

How strong is the result?

The upper end of the primary confidence interval is 0.99, so the main result barely clears conventional statistical significance, and the stronger as-treated estimate depends on who took the product often enough to count. Most outcomes were self-reported, with biomarkers as secondary measures, and the biomarker difference appeared only in the as-treated analysis. The weekly counselling is itself a recognised approach to alcohol problems, so both groups were receiving an active element; the placebo group's average barely moved, though.

The authors conclude that kudzu may be a helpful pharmacologic treatment for binge drinking among people with AUD. UCSF says larger studies are needed to confirm the findings in broader populations. That is a fair reading of a phase 2b trial: a credible, NIH-funded signal that justifies a bigger trial, and not yet a reason to treat a bottle of kudzu as a plan.

Earlier kudzu research is mixed

A smaller 2026 study from McLean Hospital and Harvard Medical School gave 19 treatment-seeking men and women with AUD either daily kudzu extract (750 mg isoflavones) or placebo, plus weekly counselling, for eight weeks. Heavy drinking days fell by about 30% on kudzu and 44% on placebo. The authors concluded that kudzu did not reduce drinking more than placebo in this treatment-seeking group. Taken with their earlier studies, they suggest kudzu may help reduce binge drinking, but may not add benefit for people already in an effective AUD programme. Before the study was funded, McLean Hospital negotiated a licensing agreement for the extract. The authors state that none of them is affiliated with the licensee.

Memorial Sloan Kettering's review of kudzu notes that human studies have mostly looked at alcohol intake or menopausal symptoms, that they enrolled small numbers of people, and that systematic reviews found the evidence of benefit for any condition unclear. The new trial adds to that literature, but it is one trial.

A supplement bought over the counter is not the study product

The trial used 2 g of standardised kudzu prepared by Natural Pharmacia International (Burlington, Massachusetts) and then over-encapsulated for blinding. It names no retail brand, and the authors say other over-the-counter products vary too much to assume the same result.

Safety and interactions

The trial data cover 12 weeks of as-needed use in a monitored setting. Kudzu's main compounds are isoflavones, and Memorial Sloan Kettering lists these points:

• Kudzu has oestrogenic activity, so people with hormone-sensitive cancers and people taking tamoxifen are advised to avoid it.
• In animal studies, kudzu reduced the elimination of methotrexate and raised its levels. Clinical relevance has yet to be determined.
• Animal studies suggest a kudzu compound may add to the effect of diabetes medicines. Clinical relevance has yet to be determined.
• Case reports include liver injury in a 55-year-old man after taking mistletoe and kudzu extracts, where it is uncertain which product, or the combination, caused it, and acute interstitial nephritis (a kidney problem) in a middle-aged woman who drank kudzu root juice for 10 days.

A case report cannot show cause, and no serious event in the new trial was attributed to kudzu. They are reasons to speak to a pharmacist or doctor before taking an extract, particularly with regular medicines.

Getting help with drinking in the UK

The NHS says a good place to start is a GP, and that Drinkline, the national alcohol helpline, is free and confidential on 0300 123 1110 (weekdays 9am to 8pm, weekends 11am to 4pm). If you have become physically dependent and need to stop completely, stopping overnight could be harmful, so get advice first about doing it safely and about any medicine you may need. Call 999 if you have severe withdrawal symptoms such as hallucinations, severe tremors or seizures.

UK rules

GOV.UK import guidance for England and Wales says food supplements, like other foods, are not required to demonstrate their effectiveness before marketing, and that they are not subject to prior approval unless they are genetically modified or novel. If a supplement claims to prevent, treat or cure a human disease, it may be classified as a medicine, so a kudzu product presented as a treatment for alcohol dependence may be classed as one. Under the Human Medicines Regulations 2012, a product is a medicinal product if it is presented as preventing or treating disease, or if it is used to restore, correct or modify a physiological function by a pharmacological, immunological or metabolic action. If a product is classed as a medicine, report a suspected side effect through the MHRA Yellow Card scheme.

FAQ

Does kudzu reduce binge drinking?

In the 120-person UCSF trial, adults with alcohol use disorder who took 2 g of kudzu extract before expected heavy drinking had fewer binge-drinking days than those on placebo, and the effect persisted for three months. A smaller 19-person trial in people already in treatment found no benefit over placebo.

Will a kudzu supplement bought over the counter do the same thing?

That is not known. UCSF's researchers caution that over-the-counter kudzu products can differ from the standardised formulation used in the trial.

Who should avoid kudzu extract?

Memorial Sloan Kettering says people with hormone-sensitive cancers and people taking tamoxifen should avoid kudzu, and says not to take it if you are allergic to it. It also says not to take it with methotrexate or diabetes medicines, and says the clinical relevance of those two interactions has yet to be determined. Talk to a pharmacist or doctor first.

What if I drink heavily every day?

The NHS says that if you have become physically dependent and need to stop completely, stopping overnight could be harmful, so get advice before doing so. Speak to a GP or call Drinkline on 0300 123 1110, and call 999 for hallucinations, severe tremors or seizures.