Kava

Supplements · Sleep & Calming Herbs · Supplement, Typed Supps

A traditional calming root with a real, documented liver warning.

Stage by stage

Intake (Extract capsule or traditional prep): Active kavalactones absorbed in the small intestine.
Small intestine (Absorbed): Absorbed alongside other plant compounds.
Liver (Processed here): Processed by the liver after circulating.
Calming brain pathways (GABA-related signalling): Interacts with calming brain signalling pathways.

What the evidence supports

Reducing anxiety — moderate evidence. Pooled trials show a real reduction in anxiety symptoms compared with placebo — better evidence than most herbal calmatives have.
Long-term safety of the liver — insufficient evidence. The reason this entry exists. Reports of severe liver injury, including cases requiring transplant, led several countries to ban or restrict it. Whether that reflects the plant, the extraction solvent, or the plant part used is still argued.

Typical dose

Trials have used roughly 60 to 280 mg of kavalactones daily, most commonly somewhere between 105 and 210 mg in divided doses. The most-studied preparation, extract WS 1490, was usually given as 70 mg of kavalactones three times a day, so 210 mg in total. The German Commission E recommended 60 to 120 mg of kavalactones daily, and for no longer than three months.

Upper limit: No formal UL, and duration matters at least as much as dose. Reported cases of kava liver injury have come on anywhere from about two weeks to two years after starting, with a median of roughly four and a half months — which is why the regulatory guidance that existed capped use at three months rather than setting a milligram ceiling alone.

Timing

Evening use is common given its calming effect.

Time to effect

~1 hr: Acute calming effect in most studies; longer-term use has more safety debate.

Medication interactions

Alcohol: Additive liver risk and additive sedation. Do not combine. (high)
Paracetamol and other hepatotoxic drugs: Compounds the liver risk that led to regulatory action. (high)
Benzodiazepines and sedatives: Additive sedation; case reports of coma in combination. (high)
Levodopa: May worsen Parkinson’s symptoms. (high)

Common myth

“Kava is a completely safe herbal alternative to anti-anxiety medication.” In reality: Rare but serious liver toxicity reports, particularly with certain extraction methods, led some countries to restrict it — a real caution, not just herbal-supplement fearmongering.