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 randomized trial has now put a standardized extract of it in front of a much wider audience. Published in the American Journal of Psychiatry on November 4, 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 randomized 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 counseling. 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 randomized): 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-randomized 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 analyzed as randomized.
• 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 counseling is itself a recognized 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 counseling, 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 program. 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 standardized 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 estrogenic 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.

Treatments with proven benefit

Three medications are approved in the United States for alcohol use disorder: naltrexone (a pill or injection), acamprosate and disulfiram, according to the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Behavioral treatments and mutual-support groups are other options, and NIAAA recommends starting with a primary care provider. UCSF notes that fewer than 10% of people with AUD have ever received medication to treat it, which is part of why researchers are looking for more options. A supplement trial is not a reason to skip a clinician.

If you have been drinking heavily for a prolonged period, suddenly stopping can trigger withdrawal that is painful or even life-threatening, with symptoms that can include seizures. NIAAA advises seeking medical help to plan a safe recovery. SAMHSA's National Helpline, 1-800-662-HELP (4357), is free, confidential and open 24 hours a day. MedlinePlus says to go to the emergency room or call 911 if seizures, fever, severe confusion, hallucinations or an irregular heartbeat occur.

US rules

FDA is not authorized to approve dietary supplements for safety and effectiveness before they are marketed. A product sold as a supplement but represented as treating or preventing a disease is regulated as a drug. The paper says the UCSF trial was conducted under an FDA investigational new drug exemption and cites pre-IND number 139735. ClinicalTrials.gov lists the kudzu arm as a drug.

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 standardized 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?

Do not stop suddenly without medical advice. NIAAA warns that withdrawal after prolonged heavy drinking can be life-threatening. Call SAMHSA's National Helpline on 1-800-662-4357, and call 911 for seizures, fever, severe confusion or hallucinations.